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 21 (BODY CONTROL MODULES)SYSTEM TESTSTEST D: SCAN TOOL DOES NOT POWER UP
1999 GMC Forward Control 5.7 R, Automatic
Test D: Scan Tool Does Not Power Up
1999 GMC Forward Control 5.7 R, AutomaticSECTION Test D: Scan Tool Does Not Power Up
WARNING: This page is about a different car, the 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, 2001 Chevrolet Monte Carlo, and 2001 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
- Check for a blown CLSTER/BCM fuse (10-amp) located in fuse block located at left side of instrument panel. If fuse is okay, check for short to ground or open in Orange wire between DLC connector terminal No. 16 and CLSTER/BCM fuse (10-amp). See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair as necessary and preform appropriate diagnostic system check for suspect system. See DIAGNOSTIC SYSTEM CHECK table. If fuse and wire are okay, go to next step.
- Check for open or high resistance in Black wire between ground and DLC terminal No. 4. See Fig 1. Repair as necessary and preform appropriate diagnostic system check for suspect system. See DIAGNOSTIC SYSTEM CHECK table. If wire is okay, go to next step.
- Check for poor terminal contact at DLC connector terminals No. 4 (Black wire) and No. 16 (Orange wire). Repair as necessary and preform appropriate diagnostic system check for suspect system. See DIAGNOSTIC SYSTEM CHECK table. If connection is okay, go to next step.
- Connect scan tool to another vehicle. If scan tool operates on another vehicle, check for poor connection between scan tool and DLC. If connection is okay, check for faulty scan tool. See scan tool manufactures instructions and repair as necessary. If scan tool does not communicate with another vehicle, check for faulty scan tool. See scan tool manufacturer's instructions, repair as necessary and preform appropriate diagnostic system check for suspect system. See DIAGNOSTIC SYSTEM CHECK table.
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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.