just put a different motor in the 94 gmc it come out of a 89 chevy van first it had a issue of to much gas change temp sensor idle air control vavle throttle position sensor egr vavle knock sensor still the same come to find out change computer it come out of it noiw the issue with the brake lights if vechiles not started they work the minute you start it they quit tail lights work find blinkers work find
My car has 132678 miles.
My car has a manual transmission.
There may be a fault in the brake light switch or corrosion crossing a circuit and making the lights work backwards. This switch is usually found on the brake pedal, but a technician with access to a wiring diagram should check the whole circuit for any other issues like loose connections or corrosion that may cause high resistance. Consider having an experienced technician, like one from YourMechanic, come out and take a closer look at the brake lighting to offer a more personal diagnosis.
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