P0703 Fault Code in Toyota: Causes, Symptoms, and Fixes

This code indicates that the Transmission Control Module (TCM) or Engine Control Module (ECM) has detected an abnormal signal from the brake switch circuit. The brake switch input is important for controlling torque converter lock-up and shift timing.

Possible Causes:

1. Faulty brake pedal switch
2. Misadjusted brake switch
3. Damaged or shorted wiring/connector in the brake switch circuit
4. Faulty TCM/ECM (rare)

Symptoms:

1. Torque converter clutch not engaging or disengaging properly
2. Harsh or delayed shifting
3. Cruise control not working
4. Brake lights may not function correctly
5. Check Engine Light (CEL) ON

Fixes:

1. Inspect and, if necessary, replace the brake light switch.
2. Adjust brake switch position.
3. Check brake switch wiring/connector for damage or corrosion.
4. Clear the code and retest after repair.