Buick Repair Questions? Ask a Mechanic for Answers ASAP
When this occurs, do the power windows still work?
Sorry for the delayed response. This source of your problem may be in the ignition switch, body control module, or the wiring. Best place to start would be to check voltage on the White wire coming off the ignition switch. If the voltage drops while the problem is occurring, replace the ignition switch. If the voltage is okay, check the wiring for any possible shorts or chafing. If wiring is okay then the body control module would be suspect.
Because the problem is affecting the dash integration module (for radio turn on signal) and the theft deterrent module, I am leaning towards ignition switch failure.
Are you removing power by cycling the key off?
Which BCM did you replace? Was it the dash integration module?
Do you have access to a scan tool?
Are there any diagnostic trouble codes stored? Do any of the modules not respond when the problem is occurring?
Two of these codes (P1381 and P1602) specifically deal with loss of serial data communications between the PCM (engine control computer) and the EBCM (abs brake control computer). Check the wiring first, the serial data wire is Purple. If the wiring looks okay, try disconnecting the electrical connectors at the EBCM and driving the vehicle (Note: ABS warning light will stay on) If the original problem does not surface with the EBCM disconnected then the problem is a short in the EBCM that is shorting out the serial data line and shutting down the radio and theft deterrent modules.