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.
Engine Control Module (ECM)
The Engine Control Module (ECM) is the main module for this function. For the Engine Control Module (ECM) the following components are included in this function:
- Relay starter motor
- Starter motor
- Battery relay (main battery)
- Secondary Battery Relay
- Coolant Pump Relay*
- Coolant Pump*
- Neutral Position Sensor**
- Clutch Pedal Switch B**
- Vacuum pressure sensor
- Alternator
- Accelerator pedal (AP) position sensor
- Stop lamp switch***
- Brake pedal switch***
- Brake pressure sensor
*Only on vehicles without Combustion Preheater Module (CPM).
** Only manual gearboxes
*** On V40 (13-) these are combined in a single component.
For a description of the relevant component, see: Design and Function - Engine Control Module (ECM)
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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.