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 DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM & COMPONENT TESTSCOMPUTERIZED ENGINE CONTROLSPCM POWER & GROUND CHECKGROUND CIRCUITS
1999 GMC Forward Control 5.7 R, Automatic
Ground Circuits
1999 GMC Forward Control 5.7 R, AutomaticSECTION Ground Circuits
- Using an ohmmeter, check for continuity to ground at PCM/VCM ground terminals. See POWERTRAIN CONTROL MODULE (PCM) CONNECTOR TERMINAL IDENTIFICATION . See Figure-Figure . Resistance should be zero ohms. If not, repair open to ground.
- Using a voltmeter, connect negative lead of a voltmeter to a good ground. Backprobe positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is more than one volt, check for open, short to voltage, corrosion or loose connection on ground circuit.
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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.