Motronic wiring diagrams

Bosch Motronic is the engine management system for the Volvo 740 Turbo (B230ET) model. Unlike newer LH injection, Motronic handles both fuel delivery and ignition with the same unit.

Below is a list of the control unit (ECU) pin functions and the wire colors connected to them: Pin Wire Color Function / Purpose 1 White Ignition coil 2 Orange Tachometer 4 Pink Starter maintenance connector / Ignition lock 5 Black Ground (crankshaft position sensor) 6 Yellow Air mass meter (AFM) 7 Brown-White Air mass meter (AFM) 8 Yellow-Red Engine speed sensor 9 Green-Yellow Air mass meter (AFM) 11 Gray-White Driver information computer control unit (pin 9) 13 White Engine temperature sensor (ECT) 14 Green-Red ETC main stage (pin 16) 16 Black Ground 18 Green Injector series resistor / ETC main stage (connects to pin 35) 19 Brown Ground 20 Yellow-Black Turbocharger boost pressure switch 21 Blue-Red CIS control unit (pin 12) 22 Green Air mass meter (AFM) 23 Black Charged air temperature sensor 25 Blue Crankshaft position sensor (CPS) 26 Red Crankshaft position sensor (CPS) 27 Blue-Yellow Engine speed sensor 30 Yellow-White Charged air temperature sensor 35 Green Injector series resistor / ETC main stage (connects to pin 18)

In many B230ET engines (and some B200 models) there is a sensor on the block above the crankcase vent cover from which a yellow wire originates. The wire turns white at the firewall penetration. It typically runs to the driver's footwell or center console. It is often an oil pressure gauge sensor or other optional gauge sensor that has also been used in EZK-ignition equipped models.

Temperature sensor: Motronic uses the same temperature sensor as the LH 2.4 system. Its resistance values are important to check if the car runs rich. CPS and speed sensors: The system has two sensors on the flywheel (pins 8, 25, 26, 27). If either of these fails, the car will not start or the ignition misfires badly.

In the Motronic system, injector control often runs through a series resistor (pin 18/35). This is a critical check point if injectors do not open, even though the pump is running.