Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit/System Description
The TCC Brake Switch signal hard wired to the TBCM is normally open and closes to battery voltage when the brake pedal is applied. A separate brake switch signal is hard wired to the Body Control Module (BCM) that is normally closed to battery voltage and opens when the brake pedal is applied. The BCM sends its brake switch information to the TBCM over GMLAN serial data. The TBCM compares the states of the two brake switch signals after a Master Cylinder Brake Pressure threshold is exceeded. If the brake switch signal states are not in agreement or if the serial data brake state is not valid, a DTC will set and the ITBC system will be disabled.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.