General description (Peugeot Eurovans 806)

The Bosch Motronic MP3.2 electronic engine management system (EMS), which has been used to control Citroen and Peugeot engines since around 1993, is an integrated system that controls the ignition coil primary winding, fuel delivery and idle speed adjustment via the same electronic control unit (ECM) (see illustration 11.1). MP3.2 is an improved version of MP3.1, in which the number of ECM contact pins has been increased from 35 to 55.



The electronic control unit (ECM) simultaneously determines the ignition timing and fuel injection duration. This way, the best ignition and fuel delivery timing is determined. The Bosch Motronic system uses the same fuel injection functions as the L-Jetronic system. A 55-pin multi-connector connects the electronic control unit to the battery, sensors, and actuators.

Main functions of the electronic control unit (ECM) (MPi)

DC voltage is supplied from the battery to contact pin No. 18 of the electronic control unit. This allows the self-diagnostic program to save data. When the ignition is on, the fuel injection system main relay supplies voltage to pin #37 of the ECU, as well as to the fuel injectors and the idle speed control valve (ISCV).



Most sensors (as opposed to those that produce voltage, for example: crankshaft angle sensor (CAS), oxygen sensor (OS)) now receive a voltage of 5.0 Volts from the corresponding contact pin of the electronic control unit. When the engine is cranking or running, the signal from the crankshaft angle sensor (CAS) causes the ECU to ground pin #3 so that the relay begins to supply voltage to the ignition coils and fuel pump. If cranking continues, the ECU will close each drive circuit by pulsing the appropriate ground wire, and the injectors, idle speed control valve (1SCV), ignition coils, and fuel pump will begin to operate.

(Original text is located at peugeotbook.ru)

Reference voltage

The initial voltage level supplied from the ECU to many sensors is 5.0 volts.

Electronic Control Module (ECM) Power Supplies and Ground Checks

Nominal battery voltage (nbv)

State	Volts
The ignition is on	11.5-13.5
When turning the crankshaft	8.0 +
With the engine running	13.0-15.9

Electronic Control Module (ECM) voltage values

Terminal numbers

ECM	Element	State	Volts
18	Battery: t30	The ignition is off	nbv
37	Relay output terminal	The ignition is on	nbv
36	Relay control circuit	The ignition is off	nbv
36	Relay control circuit	The ignition is on	1.25 (maximum)
3	Relay control circuit	The ignition is on	nbv
3	Relay control circuit	When cranking the crankshaft/the engine is running	1.25 (maximum)
14, 19, 24 and 47	ECM grounding	The ignition is on	0.25 (maximum)

Note: nbv is the nominal voltage of the battery (see illustrations 11.2, 11.3, 11.4, 11.5, 11.6)