Torque Converter/Brake Switch B Circuit High
Diagnostic trouble code P0724 indicates that the Powertrain Control Module (PCM) has detected a high voltage signal in the torque converter clutch (TCC) brake switch 'B' circuit. This typically means the PCM sees the brake pedal as constantly depressed, which prevents the torque converter clutch from engaging.
While not usually an immediate safety hazard, this code prevents the torque converter clutch from locking up, which can lead to decreased fuel economy and potential transmission overheating on long highway trips.
Common symptoms
- Check Engine Light illuminated
- Cruise control inoperative
- Decreased fuel economy
- Transmission fails to lock up at highway speeds
- Brake lights may remain on continuously
Likely causes
- Misadjusted or faulty brake light switch
- Blown brake light bulb or incorrect bulb installed
- Short to power in the brake switch 'B' circuit wiring
- Corroded or damaged electrical connectors in the brake switch circuit
- Faulty torque converter clutch solenoid (less common)
- Failed Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Check the operation of the brake lights.
Look for: Verify if the brake lights are staying on constantly without the pedal being pressed, which indicates a misadjusted or stuck brake switch.
Inspect the brake light bulbs.
Look for: Look for blown bulbs, incorrect bulb types (like single filament instead of dual), or LED bulbs installed without proper load resistors, which can backfeed voltage into the circuit.
Test the brake switch adjustment and operation.
Look for: Using a multimeter, check for continuity changes when the pedal is pressed and released. Ensure the switch is properly adjusted to contact the pedal arm.
Inspect the wiring harness and connectors for the brake switch circuit.
Look for: Look for chafed wires, melted insulation, or water intrusion in the connectors that could cause a short to power.
Monitor the brake switch PID using a scan tool.
Look for: Observe the scan tool data to see if the PCM recognizes the brake pedal state changing from ON to OFF when the pedal is cycled.
This page explains the generic P0724 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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