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.
Movement Sensor (IMS)
The movement sensor (IMS) is in the interior light in the ceiling. The movement sensor (IMS) is used to detect movement inside the passenger compartment when the alarm is activated.
When the alarm is activated, the central electronic module (CEM) checks the sensor.
The sensor communicates serially with the central electronic module (CEM).
When the sensor is activated it sends out ultrasound into the passenger compartment. The sound waves are reflected back to the sensor by the vehicle interior and if the sensor detects change in reflections or movements in the passenger compartment then the alarm is triggered. The sensor is also sensitive to air turbulence and therefore all windows and roof hatch, if appropriate, must be closed so that the sensor shall function optimally without the risk of false alarms.
Due to the sensitivity of the sensor, the alarm can be triggered if an external passenger compartment heater is used for example.
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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.