ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsHard
A vehicle's power windows operate normally, but the power door locks are inoperative on all doors. A technician checks the fuse box and finds no blown fuses related to the door lock system. What is the most likely cause?
- AA faulty body control module (BCM).
- BA faulty master power window switch.
- CA broken wire in the driver's door harness.
- DA faulty multi-door lock actuator.
Show answer & explanationAnswer & explanation
Correct answer: A. A faulty body control module (BCM).
Since all door locks are inoperative, and the power windows (which often share circuits or modules with door locks) are working, the issue points to a central control unit. The BCM (Body Control Module) commonly controls power door locks and a fault within it could disable all locks while leaving other functions intact.
Why the other options are wrong
- B. A faulty master power window switch would primarily affect window operation, not all door locks while windows are functional.
- C. A broken wire in the driver's door harness would typically only affect the driver's door lock or other components specifically in that door, not all door locks.
- D. While individual door lock actuators can fail, it is highly unlikely for all of them to fail simultaneously, making a central control fault more probable.
BCM Functionality
The Body Control Module (BCM) is an electronic control unit that monitors and controls various electronic accessories in a vehicle's body, such as power windows, door locks, lighting, and security systems.
- Centralized control for body electronics.
- Can affect multiple seemingly unrelated systems.
- Often communicates via CAN bus.
Memory trick: Many accessories, one brain – the BCM.