Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Starter motor
Manual transmissions
The starter motor (6/25) is operated by turning the key in the ignition switch (3/1) to position III.
- For transmissions with a clutch interlock (certain markets), a signal is transmitted from the ignition switch to the engine control module (ECM) (4/46). The engine control module (ECM) detects the position of the clutch pedal sensor (7/123). The engine control module (ECM) transmits data to the central electronic module (CEM) (4/56) via the control area network (CAN) about the position of the pedal. The central electronic module (CEM) requires a signal that the clutch is pressed down and that the key is in position III before it will send a signal to the relay (2/35). When the relay is activated, the solenoid in the starter motor is powered
- For transmissions without clutch interlock, the central electronic module (CEM) (4/56) activates relay 2/35 and powers the solenoid in the starter motor (6/25).
The starter motor turns for as long as the key is in position III. If the engine has been started once, there is a Limp Home function so that the engine can be started again even if there is a fault in the control area network (CAN). This function is active for a brief period after the key is removed from the ignition switch. After this time the car will not start because there is no communication for the immobilizer between the central electronic module (CEM) and the engine control module (ECM).
Automatic transmission
The starter motor (6/25) is operated by turning the key in the ignition switch (3/1) to position III.
- For transmission 4T65EV, a signal is transmitted from the gear-shift position sensor (3/71) via the transmission control module (TCM) (4/28) to the central electronic module (CEM) (4/56) indicating that the gear selector is in position P/N
- For AW transmissions the signal is transmitted directly from the gear-shift position sensor to the central electronic module (CEM). The central electronic module (CEM) requires this signal and a signal indicating that the key is in position III before it will send a signal to the relay (2/35). When the relay is activated, the solenoid in the starter motor is powered.
The starter motor turns for as long as the key is in position III. If the engine has been started once, there is a Limp Home function so that the engine can be started again even if there is a fault in the control area network (CAN). This function is active for a brief period after the key is removed from the ignition switch. After this time the car will not start because there is no communication for the immobilizer between the central electronic module (CEM) and the engine control module (ECM).
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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