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DTC codes / P07xx · Transmission / P0724

P0724Brake Switch 'B' Circuit High

P0724 means the transmission control module (TCM) sees the brake switch 'B' circuit stuck at a high voltage when it expects the signal to change as the brake pedal is pressed and released. The TCM uses this switch to know when the brakes are applied, and a constant high reading prevents it from correctly managing torque converter lockup and shift scheduling.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • The check engine light or transmission warning light is illuminated on the dashboard.
  • Often no symptoms besides the warning light, with the vehicle driving normally.
  • Harsh or delayed transmission shifts, especially when coming to a stop or accelerating from a stop.
  • The torque converter clutch may stay engaged too long, causing the engine to shudder or stall when braking to a stop.
  • In some vehicles, the transmission may fail to downshift properly as you slow down.
  • Cruise control may become inoperative or disengage unexpectedly.

Common causes, most likely first

  1. A faulty brake pedal position switch (brake light switch) that is stuck closed or has failed internally.
  2. A misadjusted brake switch that does not fully release when the pedal is at rest.
  3. A short to voltage in the brake switch 'B' signal wire between the switch and the TCM.
  4. Corroded, loose, or damaged electrical connectors at the brake switch or TCM.
  5. A defective TCM that incorrectly interprets a normal brake switch signal as high.
  6. Aftermarket accessories wired into the brake circuit, such as trailer brake controllers, causing voltage backfeed.

How to diagnose and fix it

  1. Check for any aftermarket wiring or accessories tapped into the brake light circuit and disconnect them temporarily to see if the code clears.
  2. Inspect the brake pedal switch for proper adjustment and operation, verifying that the switch opens and closes the circuit as the pedal moves.
  3. Test the brake switch 'B' circuit for a short to voltage using a digital multimeter, checking the signal wire at the switch and at the TCM connector.
  4. Inspect all related connectors and harnesses for corrosion, loose pins, or chafed wires, and repair as needed.
  5. If the switch and wiring test good, substitute a known-good brake switch to see if the code returns.
  6. Clear the code and perform a road test that includes several brake apply and release cycles to confirm the repair.
  7. If the code persists after all external checks, diagnose the TCM and its software, including checking for technical service bulletins or reprogramming.

Brake Switch B Circuit High Mysteries

  • A brake switch that is simply out of adjustment can set P0724 without any visible brake light malfunction, because the TCM monitors a separate signal circuit from the brake light output.
  • Aftermarket remote starters or alarm systems that tap into the brake wire are a frequent hidden cause of a high voltage reading on the brake switch 'B' circuit.
  • The code does not always mean the switch itself is bad; a short to voltage in the harness from a rubbed wire near the pedal assembly is just as common.
  • Some vehicles use a dual-contact brake switch where one contact feeds the brake lights and the other feeds the TCM, so the brake lights can work perfectly while the TCM signal is faulty.
  • A failing TCM can misinterpret a normal brake switch signal, so always rule out wiring and the switch before condemning the module.

Can I keep driving with P0724?

You can usually continue driving with P0724, but avoid aggressive acceleration and be aware that the transmission may shift harshly or the torque converter clutch may stay engaged, which can affect braking feel. Have the fault diagnosed soon to prevent unnecessary wear on the transmission.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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