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.
Door Open Sensor
The door open sensor is a switch mounted in the lock units of the side doors and the tailgate/trunk lid. On vehicles with an alarm there is a single switch on the hood. The switches are closed when the door or tailgate/trunk lid is shut.
The C30 and C70 do not have door open sensors for the rear side doors as they do not have any rear doors.
When the alarm is activated, the central electronic module (CEM) checks every 3 times / second that the switches are closed. If the central electronic module (CEM) detects that a switch is open the alarm is triggered.
If the central electronic module (CEM) detects that a switch is not closed when the central locking and alarm activation command is received, the vehicle tilt sensor and mass movement sensor module (MMS) alternatively ultrasonic sensor module (IMS) will not be activated. Similarly, no attention will be paid to signals from a door open sensor not closed on activation.
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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.