1. Diagnose the Problem:
* Check for obvious symptoms: Common symptoms of a failing BCM include malfunctioning lights (headlights, taillights, interior lights), power window issues, central locking problems, anti-theft system malfunctions, instrument cluster errors, and problems with the communication system (like OnStar). Don't jump to conclusions – some of these issues could have other causes.
* Use an OBD-II scanner: A scan tool can read diagnostic trouble codes (DTCs) that might pinpoint the BCM as the culprit or point to a different issue. A more advanced scanner capable of communicating with the BCM directly is preferable.
* Consult a repair manual: A factory service manual for your specific year and model Rendezvous will have detailed diagnostic procedures and wiring diagrams.
2. Troubleshooting Options:
* Check fuses and relays: Before assuming the BCM is bad, inspect all relevant fuses and relays. A blown fuse or faulty relay could be the actual problem and save you a significant expense.
* Check the BCM connections: Ensure all connectors to the BCM are securely plugged in. Corrosion or loose connections can cause intermittent problems.
* Have a professional diagnose it: This is highly recommended. A qualified mechanic with diagnostic equipment can accurately determine if the BCM is truly at fault. They can also check for related problems that may have been caused by the BCM failure.
3. If the BCM is confirmed bad:
* Replacement: The BCM needs to be replaced. This is *not* a DIY job for most people. It involves complex programming and potentially security measures. Replacing it incorrectly could cause serious problems or even brick your vehicle's electronics.
* Reprogramming: Once a new or refurbished BCM is installed, it must be programmed to your vehicle's specific settings. This requires specialized diagnostic software and equipment that's only available to professionals. Using incorrect programming can render the vehicle unusable.
* Cost: Replacing a BCM can be expensive, both for the part itself and the labor involved in installation and programming.
In summary: Don't attempt to replace or repair a BCM yourself unless you have extensive automotive electrical experience and access to the necessary diagnostic and programming tools. It's almost always best to take your Rendezvous to a qualified mechanic or dealership for diagnosis and repair of BCM-related issues. The cost of professional help will likely be far less than the potential cost of misdiagnosis, incorrect replacement, or damage to other vehicle systems.
