XC90 AWD V8-4.4L VIN 85 B8444S (2005)
Engine Control Module: Description and Operation
The starter motor (6/25) is supplied with power via the starter motor relay (2/35), the starter motor relay is controlled by the engine control module
The start process is as follows:
1. The ignition key is turned to start position (position III)
2. A high signal (Ubat) from the ignition switch (3/1) is transmitted to the engine control module (ECM) via the central electronic module (CEM).
The engine control module (ECM) interprets this high signal as a request to activate the starter motor.
3. The engine control module (ECM) activates the starter motor solenoid by grounding and powering the coil for the starter motor relay.
4. The relay closes the circuit between the starter motor solenoid and the fuse in the relay/fuse box in the engine compartment, activating the starter
5. The engine control module (ECM) activates the starter motor until the engine starts (the engine speed (rpm) exceeds a certain value)
If the ignition key returns to ignition position (position II) before the engine is started, the starter motor continues to run. The starter motor runs until the
engine is started or until a certain time has elapsed. The engine temperature dictates the running time of the starter motor:
0° C or higher, approximately 3 seconds
less than 0° C, up to approximately 5 seconds.
If the engine does not turn or if the engine speed is extremely low when the start relay is activated, the engine control module (ECM) interrupts start
Activation of the starter motor is not permitted or is interrupted if:
the engine is running (the engine speed (RPM) above a certain value)
the immobilizer function does not allow a start. For further information also see Design and Function, Immobilizer