Do NOT drive the vehicle in this condition. Driving with these issues could be extremely dangerous. The vehicle could unexpectedly shift gears or stall, and the constant drain on the battery from the blower motor will quickly deplete it.
Here's what you should do:
* Don't attempt to troubleshoot this yourself unless you have extensive automotive electrical experience. Improper troubleshooting could worsen the problem.
* Disconnect the battery negative terminal immediately. This will stop the blower motor and prevent further damage.
* Have the vehicle towed to a qualified mechanic or GMC dealership. They have the diagnostic tools and expertise to identify and repair the underlying electrical fault. Describe the problem precisely to them.
Possible causes (that a mechanic should diagnose):
* Faulty ignition switch: This is a primary suspect, as it controls power to various systems, including the transmission shift interlock and blower motor.
* Short circuit: A short in the wiring harness could be supplying power to these systems inappropriately.
* Faulty BCM (Body Control Module): The BCM controls many electrical functions in the vehicle; a malfunction could be responsible.
* Faulty neutral safety switch: This switch prevents the vehicle from shifting out of park unless the brake pedal is depressed and the transmission is in neutral. A failure could allow shifting out of park without the key.
Get professional help right away. Ignoring this could lead to further damage or a dangerous driving situation.
