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.
Code P090, TCC Brake Switch Input Circuit Problem: Action
Traction control disabled. PCM disables cruise control and substitutes status of stop/BTSI/cruise brake switch input for TCC brake switch input. "TRACTION DISABLED" and "REDUCED ENGINE POWER" message displayed on DIC. Garage shift adapts are maintained at current levels.
- Testing TCC brake switch input to PCM PI71. If input is working correctly, display will change from HI to LO to HI. If display remains HI, check circuit No. 420 and TCC brake switch for short to voltage. If display remains LO, check circuit No. 420 for open or short to ground.
- Checks for voltage at TCC brake switch terminal "A".
- Checks circuit No. 741 for short to ground.
- Checks circuit No. 420 for short to ground. If circuit is okay, check circuit No. 741 for open.
- Checks circuit No. 420 for open.
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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.
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