Manual on how to install and connect SECU-3T unit

The installation manual of the SECU-3T ECU includes following sections:

Choosing a place for mounting of unit
Block diagram of the system
The appearance of unit connectors
General recommendations on wiring
Methods of spark distribution
Connecting crankshaft position sensors (CKP, reference, Hall sensors)
Connecting camshaft(phase) sensor
Connecting the coolant temperature sensor (CLT)
Connecting the intake air temperature sensor (IAT)
Connecting the manifold absolute pressure sensor (MAP)
Installing the nipple in the intake manifold
Connection and installation of the knock sensor (KS)
Throttle limit switch or TPS
Connecting to the gas valve or switching tables
Vehicle speed sensor (VSS)
Connection of the oxygen sensor (EGO)
Additional inputs/outputs
Starter relay control
Idle cut off valve
Power valve
Connection of the engine cooling fan
Embedded stroboscope connection
Feeding signal to a tachometer
Control of the electric fuel pump
Connection of a power management relay
Connecting the automatic choke control unit
Connecting stepper gas valve
Connection of the stepper IAC valve
PWM IAC valve connection (single or double winding)
Fuel injectors
Ignition coils
Connecting iButton for immobilizer
Jumpers inside the unit (Bl, DE)
Splitting ADD_IO2 on input and output
Connecting an embedded MAP sensor
Connecting CE lamp

Installation manual for the old version of unit with 24-pin connector is here

Choosing a place for mounting of unit

SECU-3 unit must be installed in the cabin, for example, under a torpedo. MAP nipple and connectors must be directed downward to avoid moisture inside (especially important in the winter).

The MAP sensor’s hose must be connected to the intake manifold.

Block diagram of the system

Examples of complete wiring diagrams can be found here. It is recommended to review these wiring schemes for a common understanding.

The following describes how to connect the various sensors and devices individually.

The appearance of unit connectors

External connectors of the SECU-3T 14+12

The most common (and an optimal) version with USB interface and built-in sensor for absolute pressure (MAP). There is also a version with RS232 interface (instead of USB), as well as without a built MAP.

View of the unit connector:

SECU with double connector

General recommendations on wiring

For a stable and reliable operation of the unit must be strictly carried out following recommendations on the connection:

1) “+” power supply must be taken as close as possible to the battery, for example, from the ignition switch or via a separate relay from the battery. Ignorance of this recommendation may result in malfunction of the unit’s microprocessor. It is strongly not recommended to take the power for unit from the points of connection of power devices (cooling fan / stove, ignition coils, starter, fuel pump, etc.)

2) Connect unit’s ground (“-“) (J7/7 contact) using individual short wire to the body (don’t connect it to a terminal of the battery!)

3) power supply of ignition coil or module must be connected using a separate wire from the ignition switch, or through a separate relay to the battery.

4) The ground (“-“) of the ignition coils or module must be connected using individual short wire to the engine or body.

5) Connecting of all sensors (MAP, CLT, CKP, reference sensor, cam sensor, KS etc) must be carried out with a shielded cables, grounding the shield as indicated in the diagrams (to the “dirty” ground (J7/7 contact), in one point around the unit).

6) “+” of ignition modules must be connected to the ignition switch, or through a separate relay with separate battery wire, ignition coil(s) separate.

7) “-” of each ignition module to be connected to the body or the engine with individual wires.

8) in the absence of special branded crimping tools, use soldering of contacts of the main terminal. for example:

 Soldering main connector contacts

Connection all other devices to perform a proper wire cross section, depending on the current consumed by them. Shielding the other than the above connections are not required.

Methods of spark distribution

There are three ways for distribution of spark in the ICE

  • using a distributor. This is the easiest way to distribute the spark on cylinders. It is desirable to alter distributor, fixing/blocking centrifugal and vacuum advance units. Modifications will help reduce the loss of spark energy in the gap. Connection: ECU unit – ignition module – coil – distributor- spark plugs.
  • “wasted spark” or semi-sequential ignition. This method is possible only for an even number of cylinder engines. In this case, each coil runs on two cylinders, i.e. spark fed directly to the two cylinders. In this case, one of the cylinders at which point the compression stroke in the other – the exhaust stroke. It turns out one spark running in “idle”. The loss is almost no spark, as the exhaust stroke spark occurs at close to atmospheric pressure and has a small energy, the primary energy is used for ignition of the fuel-air mixture in the cylinder of the compression stroke. For example, a 4-cylinder engine needs two ignition modules/coil drivers and two coils with double high-voltage outlets or a single ignition coil with quad high-voltage outlets, for 6-cylinder engine – 3 ignition modules/drivers and 3 coils with two high-voltage outlets etc.
  • full sequential ignition. The most progressive method of the spark distribution. Each cylinder has a separate ignition module/driver and coil (usually COP). The powerful sparkle among mentioned methods. Also, this is the only way to get a power spark on engines with odd numbers of cylinders. Mandatory condition – the presence of the cam sensor, except 1-cylinder engine.

Connecting crankshaft position sensors (CKP, reference, Hall sensors)

SECU-3 unit supports synchronization from:

  • Hall sensor in distributor The easiest method of synchronization. Hall sensor in distributor is used, centrifugal and vacuum advance units are thrown out or blocked. Trigger wheel (interruptor) is standard – number of rod/gaps is equal to the number of cylinders. Can be used only with mechanical high voltage distributor. Wiring of a Hall sensor:

SECU-3T. Connecting a Hall sensor

Distributor (or trigger wheel / interrupter) must be turned 60 ° before a TDC (60° at crankshaft or 30° at camshaft/distributor). Gap in interrupter must enter sensor 60° befor TDC (this is a starting point for ignition timing). The main thing is to start the engine, and the exact initial ignition timing can be set using a stroboscope. In addition, the unit must be written with firmware with support of synchronization from a Hall sensor.

  • CKP sensor. Use a sensor installed in front of the trigger wheel (60-2, 36-1 or the other with the number of teeth 16 to 200 and 1 or 2 missing teeth). This way of synchronizing the most preferred because of its support at car factories and in the simplicity of installation and configuration.

Connecting CKP sensor (VR)

It is necessary to position the sensor correctly with respect to trigger wheel. For example, using a 60-2 pulley/trigger wheel for 4 cylinder engine, it is recommended that when the first cylinder is in TDC, center of 20-th tooth must be opposite to the sensor (so, gap will be 20 teeth before TDC). The numbering starts with 1, considered in the direction opposite to the rotation. The software allows you to select the appropriate number of teeth before TDC in a certain range. In the list of options offered for editing in the manager, there is a special option, it is called «Number of teeth before TDC».

However, it should be understood that the sensor positioning standard designed to gap (1 or 2 missing teeth) passed the sensor core at the moment of maximum angular speed of the crankshaft, at which point the acceleration is minimum. Thus, the maximum accuracy of gap recognition is achieved. For details, see installing the CKP sensor

To determine the pins 1 and 2 of CKP sensor it is possible to carry out the following experiment (with LED).

If a metal object quickly moved away from the sensor and the connected LED flashes, then the cathode of the diode corresponds to the J5/9 pin of the unit’s connector, and the anode, respectively, J5/3 pin. In case of this connection, negative front/edge for CKP sensor should be selected in the SECU-3 Manager. Anyway, you can connect sensor as you wish and select necessary front in the software, as mentioned. So, swapping of wires is equal to changing of edge in the software.

If your CKP sensor is hall effect, then you can connect it as following:
Connecting hall effect CKP sensor to CKPS1
Or this way (PS should be reassigned to CKPS):
Connecting hall effect CKP sensor to PS. PS should be remapped as CKPS.

  • Two CKP sensors (VR). This method of synchronization used with non-missing tooth wheels and separate rod mounted on the crankshaft. First sensor detects passing of teeth and second one (reference sensor) detects passing of rod. Such sensors are often installed on the flywheel, because it is already has teeth.

Connecting two VR sensors

Determination of sensor polarity is equal to determination of CKP sensor polarity described before. For reference sensor cathode of LED correspond to J5/12 pin of the external connector, anode of LED- to J5/6 pin. Correspondingly, in the SECU-3 Manager in reference sensor settings, falling edge should be set.

Connecting camshaft(phase) sensor

SECU-3 allows to use a phase sensor for full sequential ignition with COP.

Wiring of Hall effect camshaft sensor:

Connecting a Hall sensor

For correct positioning of cam sensor, it is necessary (when retrofitting a distributor):

  • set crankshaft in the position, when missing teeth will be opposite to the CKP sensor (for systems with missing tooth wheel and single CKP sensor) or reference rod will be opposite to reference sensor (for systems with non-missing tooth wheel and two CKP sensors), in the compression stroke of the first cylinder.
  • install cam sensor in a such way, that center of gap in the interrupter wheel will be opposite the cam sensor (for interrupters of type #1 and type #3, see below picture). For interrupter of type #2 (again, see mentioned picture), a center of the tooth should be opposite to the sensor and in the software settings (SECU-3 Manager) you should set inversion check for cam sensor input.

The aim of installing/connecting a cam sensor is to obtain a single pulse per engine cycle (4 strokes) in the time slot in 70° to 160° before TDC of the 1-st cylinder (compression stroke), but not late than last tooth of trigger wheel (usually, falling edge appears several teeth befor a gap or reference pulse). Oscillogram of signals looks like shown on the following picture:


SECU-3T unit has 6 independent ignition channels, by desire this number can be increased to 8 (if you remap in the SECU-3 Manager other free outputs to 7 and 8 ignition channels).
Moreover, cam sensor is necessary when using SECU-3 with two knock sensors on the V-type engine (e.g. V-8).

Below table shows order of ignition channels firing, so take it into account when connecting coil/spark plugs according to firing order of your engine.

1 1
2 1 2
3 1 2 3
4 1 2 3 4
5 1 2 3 4 5
6 1 2 3 4 5 6
8  1 2 3 4 5 6 7 8

In case of cam sensor failure, system will automatically go into the pairwise-parallel ignition mode, CE will light up and corresponding error code will be stored in the ECU memory.

In general, there are two variants of cam sensor installation (one of them already mentioned above).
First variant. Sensor has already installed or its installation was foreseen by design of engine (e.g. special seats for installing are present).
Second variant. Our engine was not completed with cam sensor, moreover, there are no special seats for sensor on the engine. In this case you can use retrofitted distributor as a cam sensor (if it is present on your engine). For that, it is necessary to make a trigger vane and if your distributor was contact, then install a Hall sensor. Take a look of the following image to see some types of trigger vane.

Interrupter wheels for cam sensor in distributor

SECU-3 hardware supports either Hall effect cam sensor or variable reluctance (VR) type cam sensor. If your cam sensor is VR-type, then you can connect it to REF_Sx inputs and in the SECU-3 Manager remap this input as PS. Separate article describing cam sensor installation can be found here.

Connecting the coolant temperature sensor (CLT)

CLT sensor must be installed in a place where the cooling liquid moves in a small circle (not through the stove or radiator cooling) closer to the exit of coolant from the engine unit, for accurate and timely determination of the temperature of the engine block. Connection:

Connecting CLT sensor

Connection of sensors with one terminal (thermistors):

Connecting of CLT with one terminal

The most commonly used sensors and a description of their terminals, see page Accessories and sensors

SECU-3 unit supports both CLT sensor types: linear characteristic and non-linear, characteristic can be set manually, by the table (for thermistors). The range of input supply voltage for CLT sensor is from 0 to 5V. Example of CLT sensor calibration described in details in SECU-3 Manager user manual.

Connecting the intake air temperature sensor (IAT)

In the regularly configured unit, IAT sensor is connected as shown on the following picture. At this you should set inversion check for ADD_O2 (see SECU-3 Manager User’s Manual).

Connecting IAT to the SECU-3T

Also, you should connect an external 2k pullup resistor (shown in grey) or solder it on the SECU-3T board as shown on one of pictures below (either):

2k resistor for ADD_I2 input

You can split ADD_I1 input and ADD_O2 output. In this case, IAT should be connected to another pin of external connector (KS_1 or MAP_S). A 2к resistor is also necessary, similarly,  you can use external one or solder it as shown on the following picture:

ADD_I2 pullup resistor

Connecting the manifold absolute pressure sensor (MAP)

If the SECU-3T unit has no built in MAP sensor, it is necessary to connect an external sensor as follows:

Connecting an external MAP sensor

By default, SECU-3T unit calibrated for MPX4250AP sensor. When using other sensors, you need to calibrate them (it is quite simple). Other sensors and description of their terminals and calibrations see on page Accessories and sensors

MAP should be connected to the intake manifold by flexible tube/hose. It is recommended to use tube with strong and thick wall, thus tube will not clench by action of the intake vacuum and as a result affect to sensor indications.

Do not connect MAP tube to the nipple on the carburetor intended for vacuum advance unit in the distributor, ignition timing in this case will not be correct!

It is desirable to connect MAP in place, where all intake manifold tubes connect together (e.g. under carburetor). If nipple for connecting of MAP sensor is absent by design, then you need to install in manually, making a hole and perform threading.
If your SECU-3T unit has an embedded MAP, then you can use MAP_S pin of external connector to lead out ADD_I2 input, which can be split from ADD_O2 output. How to do this, described in this article. This will allow you to obtain additional free input or output.

Installing the nipple in the intake manifold

Drilling a hole and cutting the thread for nipple is possible without uninstalling the manifold. The nipple can be purchased at stores selling gas-cylinder equipment. The main enemy when doing this operation – sawdust and chips. Grease the drill with lubricate and drill with minimal effort, especially at the end. It is need to update lubricant as often as possible, removing the waste with sawdust from drill. After finishing of drilling remove the remaining dust with a vacuum cleaner. Next, cut a thread also with lubricant and after again do vacuuming. To prevent nipple from unscrewing, use a liquid thread lock.

Connection and installation of the knock sensor (KS)

Connect knock sensor with shielded cable and install it in the place, provided by manufacturer of engine. If such provided place is absent, then, sensor sould be installed on bolt at the middle of cylinder block, near to combustion chambers. Pay special attention when screwing the bolt, use a torque wrench, to apply precisely a specific torque (as described in the sensor’s specification).

Connecting a knock sensor

Basically, engine knock frequency affected by the diameter of the piston, but the exact frequency, you can only learn by writing detonating sound of the engine and carrying out a spectral analysis of the resulting audio file. Often, the spectral analysis can found also the second harmonic of detonation. You can try to adjust the detection of knock on it. Sometimes it gives better results.

For details on adjusting of knock settings see здесь or SECU-3 Manager user manual.

Throttle limit switch or TPS

There are two type of determining throttle position. First is simple one – using a limit switch (which triggers when throttle closes/opens). Second one is potentiometer (output voltage depends on the position of throttle).

In case of simple limit switch, wiring is also simple:

Connecting the throttle limit switch

Connected directly to the SECU-3 unit, if necessary you can inversion in the software (so, doesn’t matter how switch triggers).

In case of using throttle position sensor (TPS) take a look of the following wiring:

Connection of the TPS

Determining  designation  A, B and C pins:

Alternately connect multimeter to the pairs of contacts and change position of throttle. Pins, resistance between which will not change when changing position of throttle are A and C, remaining pin is B.

If your engine has regular TPS sensor with ECU installed on the factory, then connect to the input of the SECU only pin B and cut special jumper on PCB (shown on the following picture).

перемычка ДПДЗ

Anyway, If you are going to connect TPS only to the SECU-3 unit, you also need to cut mentioned jumper, because it connects a pull up resistor, which will disturb normal operation of TPS. If you use a limit switch and jumper was already cut, then you need to restore it again.

You need to properly configure a limit switch or TPS in the SECU-3 Manager, so when you push a gas pedal, yellow light should appear on the corresponding indicator (for more information see  SECU-3 Manager user manual).

Connecting to the gas valve or switching tables

Connection to the gas valve allows automatically switch between set of tables when fuel type changes, for instance, between gas/petrol  (if gas equipment installed). connected directly to the SECU unit.

подключение к газовому клапану

If gas equipment is not installed on your vehicle, then you can utilize this input for switching between set of tables. For instance, “Economical” and “Power”. which set of tables to use for certain type of fuel is set in the software (SECU-3 Manager).

for this purpose you need to install a button, which will short this input to +12V:

переключние между настройками кнопкой

If button is pressed, then system will switch to the set of tables selected for gas. If button is not pressed, then system will switch to the set of tables selected for petrol.

Moreover, software allows to remap one of free inputs as MAPSEL0. In this case you have opportunity to switch between four sets of tables! Behaviour can be described by the following table:

GAS_V MAPSEL0 Set of tables
0 0 Set selected for petrol
0 1 1-st set
1 0 Set selected for gas
1 1 2-nd set

Implementation examples.
1. Rotary switch with four positions. GAS_V and MAPSEL0 inputs are connected to the switch.

Using rotary switch for switching between four sets of maps
2. Simple button (on/off) connected to the input which remapped as MAPSEL0, while GAS_V input is connected to the gas valve. So, as for petrol and as for gas, you can select between pair of table sets. For example: petrol/economical, petrol/power, gas/economical, gas/power.

Warning! As by default ADD_I2 input and ADD_O2 output are connected together and to the same pin of the external connector, (ADD_IO2), then if you are going to use ADD_I2 as MAPSEL0 you have to feed it with signal not directly from button, but via 100…200 Ohm resistor. In opposite case, when 12V will be directly come to this pin ADD_O2 transistor can be damaged. Also, when do remapping in the SECU-3 Manager, don’t forget to set inversion check for ADD_O2, thus output transistor will always be turned off and doesn’t disturb working of ADD_I2 (MAPSEL). As option, you also can solder out output transistor  VT3, (in this case resistor mentioned above is not needed) or even more, you can perform actions described in this article.

Vehicle speed sensor (VSS)

Vehicle speed sensor can be also connected to the SECU-3T unit. VSS outputs certain number of pulses per 1Km of passed path.

VSS connected to the PS or REF_S1 inputs. Following wiring shows how to connect it to the PS input:

Connecting VSS

You need to specify in the settings of the SECU-3 Manager program number of pulses per 1Km. Also, in the software don’t forget to remap PS input as SPD_SENS. If you connected VSS to REF_S1, then you also need to pull up this input with 1k resistor to MAP+ or 12V, and correspondingly, in the software remap REF_S input as SPD_SENS. Pull up for REF_S1 can be soldered as shown on the picture:

Pull up for REF_S1

After that, SECU-3 Manager will display vehicle speed and passed distance since last starting of the engine.

Connection of the oxygen sensor (EGO)

Connection of the narrow band oxygen sensor is shown on the scheme below:
Sensor with heating:


All possible options for controlling of sensor’s heating are shown on the following picture. Option A allows to use PWM control, which extends lifetime of sensor (for some sensors PWM control is obligatory, see technical specification on your sensor).

Options to control of lambda sensor's heater

If you need to emulate correct mixture while oxygen sensor is heating up, you can use following wiring:

Emulation of correct mixture while oxygen sensor is heating up

SECU-3 unit has no PWM output for controlling of the oxygen sensor’s heating in pulse mode. In this connection, if model of oxygen sensor allows, then its heating should be connected to work permanently or being controlled from the SECU-3T unit by means on one of outputs, remapped as universal (universal programmable outputs, see SECU-3 Manager).

Additional inputs/outputs

SECU-3 unit has two additional inputs/outputs (ADD_IOx, see pinouts), which like other outputs and inputs can work in different modes. Mode of operation can be programmed via SECU-3 Manager software. These I/O can carry out following functions:

  • stroboscope mode
  • emulation of the conventional Hall sensor output for feeding of another ECU (e.g. throttle-body injection ECU) or a tachometer
  • control of the electric fuel pump
  • control of the SECU-3T unit’s supply  (unit takes supply directly from the battery via relay and can work some time after turning off of ignition to perform or finish some tasks).  One input and one output are used.
  • control of the automatic choke via stepper motor unit. Two outputs are used.
  • control of the stepper gas valve
  • activation of blink codes (used to display ECU errors stored in the memory)
  • additional input for switching between 4 sets of tables
  • control of the intake manifold heating
  • input for VSS
  • universal programmable outputs (firmware supports up to 3 such outputs)
  • control of one or several fuel injectors (via external driver)

It is worth noting, that ADD_IOx can be split into separate inputs and outputs (they are already separated in the software). Starting from the RevC U6 board, ADD_IO1 (J5/10) by default is split (output is left on the ADD_IO1 pin, but input is connected to KS_2 pin). Starting from the  RevD U6 board, appeared opportunity to split in a such way ADD_IO2 (only in case, if detonation control is not used, because in this case ADD_I2 input will be connected to KS_1 pin). If unit with embedded MAP, then MAP_S is free and can be also used to lead out ADD_I2. Both of mentioned variants are described in this article.

Starter relay control

Additional starter relay (or starter blocking relay) turns off starter after cranking if RPM exceeds set threshold. This feature essentially increases life of the starter.

By default, if engine RPM exceed 600min-1, ST_BLOCK output is being turned off. Coil of the starter relay connected between ST_BLOCK and +12V  from the ignition switch. Normally open relay contacts connected  to open in the wire coming from the ignition switch to the starter solenoid as shown in the diagram below:

starter blocking relay

Idle cut off valve

Body of the valve connected to engine (ground), thus only one wire comes from the SECU3T unit. If valve has two terminals, connect one of them to to the body or engine, second terminal connect to the IE output of the SECU-3T unit. Use wire with good isolation and with enough cross section (with will reduce probability of break). If wire of valve will broke, then engine will stall if gas pedal is released.

Connection of the idle cut off valve

Power valve

Body of the valve connected to engine (ground), thus only one wire comes from the SECU3T unit. If valve has two terminals, connect one of them to to the body or engine, second terminal connect to the FE output of the SECU-3T unit. Use wire with good isolation and with enough cross section (with will reduce probability of break).

Wiring of the power valve

Not all carburetors have such valve in “electronic form”, but for Solex carburetors it is possible to manufacture special adapter and control mentioned valve from the SECU-3 unit. This will optimize control of the fuel mixture on high load engine modes. Designs of the adapters (several variants) can be found this page Installing the power valve.

Connection of the engine cooling fan

There are several variants of the engine cooling fan control:

Using a relay, simple method, allows to turn on cooling fan when coolant temperature reaches set threshold and to turn off cooling fan when temperature falls below another specified threshold. On/off thresholds can be set from the SECU-3 Manager software.

Connecting cooling fan using relay

Using a cooling fan control unit with PWM. This method allows control RPM of the cooling fan smoothly, thus decreasing noise, increase its life and flatten engine temperature swings. Threshold when cooling fan will be 100% turned on is set from the SECU-3 Manager. Minimal speed will be turned on before 6° to the threshold. Wiring diagram is shown below.

Smooth control of the cooling fan's speed

It is recommended to use shielded wire for the ECF signal, but it is not obligatory.

Warning! Connections which shown by thick lines should be made with appropriate cross section wires. Through these wires will frow current which is equal to the current of your cooling fan.

In such connection, the fan will be turned off when you turn off the power of the ECU.

If you want cooling fan to be controlled from the regular thermostat when ignition is turned off, then use following wiring diagrams by your choice:

  • when using regular relay for on/off control (without smooth control):

параллельное управление вентилятором

Warning! Connections which shown by thick lines should be made with appropriate cross section wires. Through these wires will frow current which is equal to the current of your cooling fan.

  • when using coiling fan speed control unit. When ignition is turned off, cooling fan will be driven by regular thermostat:

joint of the cooling fan control from the thermostat and SECU

Warning! Connections which shown by thick lines should be made with appropriate cross section wires. Through these wires will frow current which is equal to the current of your cooling fan.

Embedded stroboscope connection

Stroboscope is used for setting or checking of the starting ignition timing using special marks on the crankshaft or pulley.

For synchronization from a Hall sensor it is obligatory to check the starting ignition timing. This is because it is hard to position a distributor with high accuracy.

Of course, you can use a conventional separate strobe (usually looks like a pistol), but SECU-3 has an embedded stroboscope function and we will describe its using beneath.

Strobe light is connected to the one of free outputs of the SECU-3, remapped as STROBE. As strobe light, 1…3 Watts LED can be used with lens. If one of the IE or FE outputs selected for strobe, then connect LED using following wiring:

подключение стробоскопа на FE-IE

For the rest of outputs, use this wiring:

подключение стробоскопа на НЕ FE-IENote, that some SECU-3 outputs have pull up resistors to 5 or 12V. This will slightly illuminate LED, but it should not be a big problem.

Feeding signal to a tachometer

Connection of the tachometer is directly depends on its type:

  • driven by low voltage signal

Tachomener should be connected to the one of outputs remapped in the software as HALL_OUT. At the same time, a 1k pull up resistor from this output to +12V is necessary.

If one of the IE or FE outputs selected for HALL_OUT, then wiring looks like following:

Connecting low voltage tachometer to the SECU-3 ECU

If other outputs selected for HALL_OUT, then use this scheme:

Connecting low voltage tachometer to the SECU

  • driven by high voltage

Again, tachometer can be connected with HALL_OUT with using of this schematic:

If IE or FE output is used for HALL_OUT:

Connecting high voltage tachometer

If other output selected as HALL_OUT:

Connecting high voltage tachometer


Coil from the conventional automobile relay can be used as inductance.

VT1 transistor can be С5027, 2SC5027, KT859A and any other high voltage.

Also, high voltage tachometer can be connected even without using of HALL_OUT (without remapping one of outputs). One of the following schematics can be used, depending on the number of cylinders.

подключение высоковольтного тахометра через диодыIt doesn’t matter you use wasted spark or full-sequential configuration. Diodes are used to mix pulses from several coils to single output. Note that anodes of diodes should be connected to outputs of ignition module (coil drivers), so to the primary winding of coil.

If  tachometer shows nothing, then try to add scheme of 1 or 2 resistors as shown at the picture below.  If that didn’t have effect, then try to select values of R1 and R2, especially R2. In most of cases R2 is unneeded and can be excluded (R=0).

You can also try a schematic with Zener diode (cathodes of diodes are connected to a Zener, which passes only high voltage pulses):


If you are not able to determine type of the tachometer (high or low voltage), then first connect it using low voltage schematic, and if it doesn’t work, finally connect it using one of the high voltage schematics.

Control of the electric fuel pump

Fuel pump can be low pressure (e.g. 0.3 bar) if installed on the carburetor or high pressure (e.g. 3 bar) if fuel injection is used.  Electric fuel pump should be connected via relay:

Подключение электробензонасоса через реле

One of free outputs should be remapped as FL_PUMP. SECU-3 unit will keep supply of the fuel pump turned on in following cases:

  • within 5 seconds after the ignition is switched on
  • permanently if the engine is running,
  • within 3 seconds after the engine stops

Connection of a power management relay

It may be necessary for ECU to perform operations some time after switching off the ignition. For instance, it can set automatic choke or IAC valve to the initial (cranking) position or keep cooling fan turned on.

SECU-3 unit should be connected directly to the battery via relay as shown on the picture below. After switching off of ignition, ECU will finish all pending operations and disconnect himself from the supply.

подключение реле управления питанием

If after turning the ignition lock into the OFF position, voltage at the ADD_IO2 (or ADD_I2) doesn’t drop below 1V, then make sure resistor R27 is soldered on the PCB (by default it is not soldered). This resistor acts as pull down to the ground. Of course, you can connect external resistor (1…10kOhm) between ADD_IO2 (ADD_I2) and ground.

Using of this power management scheme will reduce the risk of damaging of the ECU’s EEPROM (which may occur if supply disappears at the moment when microprocessor writes some data to the EEPROM).

For working of mentioned scheme, you need to remap one input and one output in the SECU-3 Manager. Set inversion check opposite to the ADD_O2 output (because ADD_I2 input and ADD_O2 output by default connected to the same pin of the external connector). Thus, output will not disturb working of the input. Also, you can do actions described in this article and as a result,  ADD_O2 will not conflict with input (mentioned inversion check and resistor shown on the schematic become unnecessary).

Connecting the automatic choke control unit

Automatic choke is driven by the stepper motor which connected to the SECU-3 unit using stepper motor control unit.


How to install automatic choke and connect motor in details see in article How to install automatic choke on the Solex carburetor

Connecting stepper gas valve

Stepper gas valve connected as already described for automatic choke – using stepper motor control unit.

Подключение газового дозатора к блоку SECU-3T

Stepper IAC valve connection

If you are going to use SECU-3T for the fuel injection, then you may need to connect and control stepper IAC valve. Below wiring shows hot to connect stepper IAC. Inputs of the SECU-STEP are connected to IGN_OUT3 and IGN_OUT4 output of the SECU-3T ECU, which should be remapped as DIR and STEP correspondingly.
Подключение шагового РХХ к блоку SECU-3T

Also, for economy of outputs (number of which is very limited) SECU-STEP inputs can be connected to the BL and DE signals inside the SECU-3T unit (see jumpers inside the ECU). But in this case you need to open ECU and solder two wires (which will go outside). It is recommended only for experienced users.

PWM IAC valve connection (single or double winding)

If you are going to use SECU-3T unit for fuel injection, then you may need to control IAC valve. Beneath described how to connect PWM IAC valve to the SECU-3T unit.

If valve has single winding (2 terminals), then use following schematic:
Подключение ШИМ РХХ c одной обмоткой к блоку SECU-3T

It is easier to use ready-made driver board SECU-PWMIAC:

Connecting single-coil PWM IAC driver to the SECU-3T unit

If valve has double winding (3 terminals), then use schematic shown below (it is slightly more complex than first one). It is possible to use TIP120-122 transistors.
Подключение ШИМ РХХ c двумя обмотками к блоку SECU-3T

Or again, it is more easier to use ready-made driver board SECU-PWMIAC:

Connecting double-coil PWM IAC driver to the SECU-3T unit

Described above schematic can be assembled on the small board or inside the box from old relay. PWM IAC valve driver also present in the SECU-P&H+PWMIAC unit, but using of this unit only for IAC is not reasonable.

Fuel injectors

High resistance injectors can be connected to the SECU-3T unit using 4-channel Hi-z injector driver board. If you need more than 4 channels, then use two such boards.

Подключение высокоомных форсунок к блоку SECU-3, попарно-параллельный впрыск

On the wiring shown above, driver connected to IE and FE, which are high side outputs (12V appears when injector should be turned on). By default pull down resistors on the 2-nd and 3-rd inputs of the driver are soldered. First input connected with second, third with fourth, thus ensured correct working from the high side outputs .

For the simultaneous injection it is enough only one output from the SECU-3T. Injector driver inputs should be connected together and to the one of ECU outputs.

Подключение драйвера высокоомных форсунок для одновременного впрыска

Following wiring diagram shows how to connect driver for full-sequential injection on the 4-cylinder engine. Like in previous wirings, second and third driver inputs are connected to IE and FE outputs.

Подключение драйвера высокоомных форсунок для фазированного впрыска

In case if 2-nd and 3-rd inputs of the driver connected to other outputs of the SECU-3 unit, then it is necessary to solder out mentioned resistors.  Instead of this, provide pull up resistors to 5 or 12V  (these are resistors provided on the SECU-3T PCB or external resistors).

Except this, if any of the driver inputs connected to the low side output, then in the SECU-3 Manager when remapping of corresponding output, set inversion check.

Peak and Hold injectors, if they are many, connected via  4-channel peak-n-hold injector driver. If you need more than four channels, then use two such drivers.

Подключение peak-n-hold форсунок к блоку SECU-3T, попарно-параллельный впрыск

In this example driver inputs are connected to the high side outputs of the SECU-3T unit. Inputs of driver should be properly configured (pull up/pull down resistors, см. schematic).

If you need to control a single P&H injector (for instance throttle body injection), then use SECU-P&H+PWMIAC unit. Wiring of the unit is shown on the below schematic:

Подключение форсунки моновпрыска к блоку SECU-3T

Unit contains P&H injector driver and PWM IAC driver, which connection is also shown on the schematic.

Ignition coils

Ignition coils connected using ignition modules, BIP373 or SECU-3 Igniters. If ignition coil has embedded driver(s), then it can be directly connected to the SECU-3T unit. ECU has 6 ignition channels (IGN_OUT1, IGN_OUT2, IGN_OUT3, IGN_OUT4, ADD_IO1, ADD_IO2) and two of any free outputs can be remapped as 7 and 8 ignition channels. Thus,  ECU supports up to eight ignition channels. By default, first 5 ignition channels have 1k pull up resistors to 5V. If you are going to use ADD_IO2 as ignition channel, then it is necessary to solder a pull up resistor (PCB has special place for it).

SECU-3T подтягивающий резистор на 6-м канале зажигания

The same goes for any other outputs remapped to be used as 7 and 8 ignition channels, but special places for the resistors are not provided on the PCB (experienced users can solder the resistors inside the unit, for the rest it is recommended to connect the resistors from outside).

How to connect ignition coil to the SECU-3T unit using ignition module is shown below:

Подключение коммутатора и катушки зажигания к блоку SECU-3T

The coil could be any: with single high voltage outlet, filled with oil, with double high voltage outlet etc.

How to connect ignition coil using BIP373:

Подключение BIP373 к блоку SECU-3

Schematic diagram shows only connection of the primary winding. On the next picture you can see an example of connecting 2 BIP373 and two double-ended coils for Wasted Spark ignition on the 4-cylinder engine. Of course, you can use single coil with four high-voltage outlets instead of pair  of coils with two high-voltage outlets.

SECU-3T BIP373 Wasted Spark 4 cylinder engine

Also, you can use SECU-IGN-DRV4 driver. Wiring diagram example for full sequential ignition on the 4-cylinder engine with mentioned driver is shown below. If your engine is 5, 6 or 8 cylinders, then, obviously you need two of these drivers.
Connecting SECU-IGN-DRV4 coil driver to the SECU-3T unit
Connecting of SECU-IGN-DRV4 driver for wasted spark on the 4-cylinder engine:
SECU-IGN-DRV4 for wasted spark ignition on the 4-cylinder engine
Connecting of SECU-IGN-DRV4 driver for wasted spark on the 4-cylinder engine with COP:
Wasted spark, 4 cylinders, coil-on-plug

Connecting iButton for immobilizer

iButton key (for example, DS1990) can be connected to the SECU-3 unit for the implementation of the immobilizer. Connection is shown on the picture below. It is desirable to use a shielded cable for connection. iButton has written code on it, this code should be entered in the security settings tab in the SECU-3 Manager.

Подключение iButton DS1990 к блоку SECU-3T


Jumpers inside the unit (Bl, DE)

SECU-3T unit has two jumpers inside:

emergency start of the boot loader.

аварийный запуск бутлоадера секу

For example, if during the flashing  something went wrong: lost power supply, hanging of computer, etc.  In this case, the unit will not operate properly and most likely will not be linked with the SECU-3 Manager. In such cases, this jumper is useful.

Installing this jumper will force boot loader to start. In this case, set in the SECU-3 Manager check “Bootloader launched emergency” to work with the unit in this mode. Now the unit can be flashed through the manager. So you can restore firmware.

To turn off this mode, the jumper must be returned to the neutral position.

– loading default settings to EEPROM

секу сброс настроек перемычкойThe unit has a special area of memory which stores its default settings. Install this jumper, turn on power supply to the unit and settings rescue mode will run. This process takes a few seconds and “CE” will light during this time. After restoring the settings, jumper  should be returned to the neutral position.

Settings resetting procedure can be launched even without touching jumpers – by software via SECU-3 Manager (see SECU-3 Manager user’s manual).

– neutral position

JMP default

Appearance of the jumpers can differ from the shown on the photo. One contact pair can be light-coloured and turned to the side or it can be dark and just sticking up (both pairs of contacts are similar).

On the bottom side of the PCB there are additional labels:

“B” – boot loader jumper (Bootloader)

“E” – jumper for loading/rescuing settings into EEPROM (default EEPROM)

Thus, you can gently close one of jumpers on the back side of the board, the board itself is not pulling out.

Splitting ADD_IO2 on input and output

If you are not using detonation control or your SECU-3T is with an embedded MAP, then you can obtain additional input or output. To do this, split ADD_IO2 into input and output. This article describes in detail how to do it. Recommended only for experienced users.


Connecting an embedded MAP sensor

SECU-3T Connecting an embedded MAP sensor

Connecting CE lamp

Подключение лампы CE

Copyright (C) Alexey A. Shabelnikov 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018,
SECU-3™ is registered trademark. Using of any materials from this site without a reference to the source is prohibited.


  1. BaNDiTR
    14.04.2014 @ 11:05 AM

    If i remap the FE output to function as HALL_OUT, will it be in synchronisation with spark signals on IGN_OUT1 or IGN_OUT2 ?

  2. STC
    14.04.2014 @ 01:19 PM

    Yes, if you remap FE to HALL_OUT, it will be in synchronization with mentioned signals.
    One pulse per engine stroke.

  3. Иван Ко-ко
    11.05.2014 @ 06:25 PM

    Я у Вас недавно купил блок(получил 30 апреля), еще не ставил пока проводку вояю.Так вот вопрос:какие функции сейчас в блоке, что подключено(стандартные).Я не знаю что такое стандарт.Из инструкции по ДАННОМУ блоку “шпаргалка”. Зачем есть на Вашем сайте.Может глупые вопросы задаю, простите.Хочу сам разобраться.Спасибо.

  4. STC
    11.05.2014 @ 07:07 PM

    Можете задавить любые вопросы (даже глупые ;-))на форуме, там и ответим подробно.

  5. n1ger
    24.06.2014 @ 10:17 PM

    В пункте “Реле блокировки стартера” на картинке в левом верхнем углу “селеноид” и в тексте тоже “селеноид”. Вроде ж как соленоид? Селеноид, по словарям, это вообще что-то с луной связано)))

  6. STC
    26.06.2014 @ 12:01 PM

    Спасибо! Поправили 🙂

  7. mv78
    11.12.2014 @ 05:41 PM

    Здравствуйте ! покупал плату вас собирал сам все работает возник вопрос можно ли установить на ниву моновпрыск блок упровления EFI-4 вышел из строя родной модуль зажигания .

  8. STC
    11.12.2014 @ 06:48 PM

    Можно, как спрашивайте на форуме

  9. Александр Сокуренко
    27.10.2015 @ 11:03 PM

    Как бы увидеть схему подключения моновпрыска.

  10. STC
    21.11.2015 @ 08:15 PM

    Схемы подключения для впрыска (и в частности моновпрыска) уже добавлены на сайт.

  11. STC
    19.10.2016 @ 12:14 AM

    Инструкция была обновлена и улучшена.

  12. serilo
    02.12.2016 @ 10:07 AM

    А есть какая-либо информация о типе ДТВ и на что вообще влияет его установка? Я в документации про это чего-то ничего не нашел.

  13. STC
    02.12.2016 @ 10:19 PM

    ДТВ используется в 2-х случаях:
    1. Коррекция УОЗ по температуре воздуха на впуске
    2. Расчем времени впрыска топлива (если прошивка с впрыском)
    ДТВ любой подойдет, так как для его настройки есть отдельная таблица.

  14. STC
    29.12.2016 @ 03:08 PM

    Полезная статья об установке ДУИ+ДНО от Nikola

  15. Родион Долгов
    11.06.2017 @ 01:10 AM

    Нужно ли проворачивать шторку модулятора датчика-распределителя зажигания на 30 градусов раньше при использовании SECU-3 Micro или это верно только для старых прошивок/других блоков SECU?

  16. A. Shabelnikov
    12.06.2017 @ 01:23 PM

    Родион, да, нужно доворачивать шторку.

  17. Igor Khrol
    14.11.2017 @ 02:05 PM

    Здравствуйте. При установке одновременного впрыска(не моно) имеет значение что установлено концевик дз или дпдз и что предпочтительней?

  18. A. Shabelnikov
    14.11.2017 @ 02:49 PM

    Для впрыска (любого) наличие ДПДЗ обязательно.

  19. Igor Khrol
    16.11.2017 @ 02:35 PM

    Будет secu-3 корректно работать на впрыске без ДК ?

  20. Igor Khrol
    16.11.2017 @ 02:51 PM

    ДК обязательно нужен для корректной работы ?(все остальные установлены).

  21. A. Shabelnikov
    17.11.2017 @ 12:12 PM

    ДК нужен для настройки и работы впрыска. Если впрыск хорошо настроен, то можно и без ДК ездить, но со временем смесь потихоньку будет уходить (износ механизмов) ну или банально бензином плохим заправитесь и все.

  22. stasoks
    16.12.2017 @ 11:52 PM

    при достижении 600об на выходе st_block пропадает минус, я правильно понял? если да то можно ли подключить данный минус на минус обмотки реле стартера (ваз 2108)? с замка будет идти плюс а с блока минус, и при достижении нужных оборотов минус пропадет и реле разомкнется? так будет проще

  23. A. Shabelnikov
    17.12.2017 @ 02:01 AM

    stasoks, Если это слаботочное реле, то можно.

  24. stasoks
    17.12.2017 @ 09:15 PM

    на какую нагрузку рассчитаны выходы? реле потребляет 200мА

  25. A. Shabelnikov
    18.12.2017 @ 12:17 AM

    В блоке SECU-3T выходы рассчитаны максимум на 500мА.

  26. Игорь Ганоцкий
    11.05.2018 @ 11:30 AM

    Здравствуйте, при прошивке блока secu 3t завис ноутбук и теперь блок не соединяется с менеджером, перемычки тоже не помогла, лампочка чек при включенном зажиганием горит постоянно, посоветуйте что делать ?

  27. STC
    14.05.2018 @ 10:19 PM

    Читайте внимательно справку по программе SECU-3 Manager. Там описано как пользоваться галочкой “Boot loader запущен аварийно”. После установки галочки нужно обязательно “передернуть” питание блока, так как состояние перемычки проверяется прошивкой только после включения питания. Вопросы лучше задавать у нас на форуме.

  28. denka6002
    27.09.2018 @ 09:05 PM

    Возможно ли запрограмировать свободный выход для управления соленойдом изменения геометрии впуска?

Leave a Reply