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.
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HOMESERVICE MANUALSGMC1991JIMMY 5.7 K, AUTOMATIC, 4L60/MD8REPAIR AND DIAGNOSIS (SINGLE PAGE)TRANSMISSIONAUTOMATIC TRANSDIAGNOSIS - A/TDIAGNOSTIC FLOW CHARTS (CARS)CODE 38, BRAKE SWITCH CIRCUIT - 3.3L PFI N BODYNOTES
1991 GMC Jimmy 5.7 K, Automatic, 4L60/MD8
Code 38, Brake Switch Circuit - 3.3L PFI N Body: Notes
1991 GMC Jimmy 5.7 K, Automatic, 4L60/MD8SECTION Notes
ECM monitors status of brake switch circuits through ECM terminal BC4. Code 38 will set under the following conditions:
- No. Code 24 is present.
- Vehicle speed has been above 35 MPH and back to 0 MPH 23 times.
- Status of circuit No. 420 has not changed state.NOTE: Test numbers refer to test numbers on diagnostic chart.
- Jumpering brake switch will determine if ECM and wiring for brake circuit are okay.
- This test verifies supply voltage to brake switch.
RENDER: 1.0x
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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.