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 MANUALSGMC1991S15 JIMMY 2D UTILITY, RWD, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)BRAKESANTI-LOCK BRAKESANTI-LOCK BRAKE SYSTEM - REAR WHEELTESTING & DIAGNOSISNOTES
1991 GMC S15 Jimmy 2D Utility, RWD, Standard
Testing & Diagnosis: Notes
1991 GMC S15 Jimmy 2D Utility, RWD, StandardSECTION Notes
NOTE:
Ensure brake warning light is on before trying to retrieve trouble code. If light is not on, grounding ALDL connector will lead to false CODE 9.
- System can be diagnosed through trouble codes. To activate trouble codes, connect a jumper wire between terminals "A" and "H" on ALDL connector and observe flashing on brake warning light. Sequence should be one long flash followed by short flashes (i.e. one long flash followed by 4 short flashes indicates CODE 5).
- System will repeat code as long as ALDL connector is grounded. Long flash after short flashes indicates repeat of code. If there is more than one failure, only the first failure code will be stored and displayed. See TROUBLE SHOOTING CHARTS .
- On C and K Series trucks with dual rear wheels, a "chirping" noise may occur when applying brakes. This is a mechanical problem, not RWAL. To correct, remove brake drums and spray two coats of Graphite Compound (12345268) onto brake linings. Allow compound to dry between coats.
NOTE:
If ECU connector retaining clip is broken when unplugging connector, service clips are available from manufacturer.
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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.