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.
DTCS 37/38, TCC Brake Switch Stuck On/Off: Notes
Normally closed brake switch supplies a B+ signal on TCC brake switch signal circuit to PCM. When brakes are applied signal voltage is opened.
DTC 37 will set when:
- TCC brake switch signal circuit is open and/or.
- Vehicle speed is less than 5 MPH for greater than 6 seconds.
- Then vehicle speed is 5-20 MPH for greater than 6 seconds.
- Then vehicle speed is greater than 20 MPH for greater than 6 seconds.
- For a total of 7 times.
DTC 38 will set when:
TCC brake switch signal circuit has constant voltage.
* Vehicle speed is greater than 20 MPH for greater than 6 seconds.
* Then vehicle speed is 5-20 MPH for greater than 6 seconds.
* For a total of 7 times.
PCM will default to an incorrect brake signal can affect TCC scheduling. Also, an incorrect brake signal can inhibit 4th gear operation, if in hot mode. DTCS 37/38 will be stored in PCM memory, but will not turn on MIL.
- This test checks for voltage at brake switch.
- This test checks brake switch.
- This test checks TCC brake switch signal circuit at PCM.
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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.