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 MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 83 (ENGINE CONTROLS - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0724: BRAKE SWITCH CIRCUIT LOWDIAGNOSTIC PROCEDURES
1999 GMC Forward Control 5.7 R, Automatic
Diagnostic Procedures
1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.
- Turn ignition on, with engine off. Using scan tool, monitor BRAKE SWITCH while depressing and releasing brake pedal. If scan tool does not indicate RELEASED when brake pedal is applied, problem is intermittent. See DIAGNOSTIC AIDS . If scan tool indicates RELEASED when brake pedal is applied, go to next step.
- Check BRAKE fuse (15-amp). Replace and retest if open. If fuse continues to open, repair short in Orange wire or Light Blue wire between underhood fuse block and PCM. Remove left side lower instrument panel cover. Disconnect stoplight switch. Connect jumper wire between Orange wire and Light Blue wire at stoplight switch connector. If scan tool consistently indicates APPLIED, check stoplight switch connector and adjustment. If connector and adjustment are okay, replace stoplight switch. If scan tool does not consistently indicated APPLIED, go to next step.
- Connect test light between stoplight switch connector terminal No. 4 (Orange wire) and ground. If test light is on, check Light Blue wire between stoplight switch and PCM for open. If wire is okay, replace PCM. If test light is off, repair open in Orange wire between stoplight switch and underhood fuse block.
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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.