A vehicle's warning chime for 'key in ignition' or 'lights on' when the door is open is inoperative. All other chimes (seatbelt, low fuel) function normally. A technician confirms the door ajar switch is operating correctly and the ignition switch properly detects the key. Which component is MOST likely faulty?
- AThe ignition switch wiring
- BThe instrument cluster speaker/chime module
- CThe door ajar switch wiring
- DThe Body Control Module (BCM)
Show answer & explanationAnswer & explanation
Correct answer: D. The Body Control Module (BCM)
The 'key in ignition' and 'lights on' chimes are typically controlled by the Body Control Module (BCM), which receives inputs from various switches (door, ignition, light switch) and then commands the chime module or speaker. Since all inputs (door switch, ignition switch, lights) are confirmed good, and other chimes work, the BCM is the most likely component that is failing to process these specific inputs and/or send the correct command for these specific chime conditions.
Why the other options are wrong
- A. The ignition switch is confirmed to be operating correctly, ruling out its wiring.
- B. If other chimes (seatbelt, low fuel) work, the instrument cluster speaker or chime module itself is functional, ruling it out as the cause for this specific chime's failure.
- C. The door ajar switch is confirmed to be operating correctly, ruling out its wiring.
Body Control Module (BCM) Functions
The BCM is an electronic control unit responsible for monitoring and controlling various electronic accessories and body functions, including interior lighting, power windows, central locking, and warning chimes.
- Acts as a central hub for many comfort and convenience features.
- Receives inputs from numerous switches and sensors.
- Processes logic and sends commands to actuators or chime modules.
Memory trick: Inputs good, other chimes ring? BCM's logic is missing a thing!