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 37, Brake Switch Stuck On: Notes
The normally closed brake switch supplies a 12-volt signal on circuit No. 420 to the PCM. The signal voltage is removed when brakes are applied. An incorrect brake signal may affect TCC and 4th gear operation in hot mode.
Code 37 will set when circuit No. 420 is open, vehicle speed less than 5 MPH for 6 seconds, then between 5 MPH and 20 MPH for 6 seconds, then greater than 20 MPH for 6 seconds, for a complete total of 7 times.
- This test checks for voltage at brake switch.
- This test simulates closed brake switch (brakes off).
- This test checks circuit No. 420 from brake switch to PCM.
- This test opens circuit No. 420 and simulates brakes being applied.
NO RELATED
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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.