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.
Diagnostic Trouble Codes (DTCS)
A diagnostic trouble code (DTC) is stored if the control module detects a fault.
A malfunction that has been detected repeatedly during several driving cycles will permanently turn off the functions adaptive cruise control, collision warning, and brake assistance as well as store a diagnostic trouble code for this.
A permanently turned off system can only be reactivated by resetting diagnostic trouble codes in the Forward Sensing Module (FSM), Central electronic module (CEM), Brake control module (BCM), and Engine control module (ECM) in the same driving cycle.
A driving cycle includes ignition on, that the vehicle speed goes above 20 km/h as well as ignition off.
If a malfunction occurs in the adaptive cruise control and brake assistance functions in case of a possible collision, a malfunction counter calculates up per function. If these malfunction counters, independent of each other, reach a predetermined value during the same operating cycle, independent error flags are stored in the monitoring logic in the Central electronic module (CEM).
Storage of this error flags also results in diagnostic trouble codes (DTCs) being stored in the Forward Sensing Module (FSM), Brake control module (BCM), Engine control module (ECM) and in the Central electronic module (CEM). The diagnostic trouble codes (DTCs) must be erased from all control modules during an operating cycle to reset these error flags.
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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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