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 533 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESBACKUP LAMPS ALWAYS ON
1999 GMC Forward Control 5.7 R, Automatic
Backup Lamps Always On
1999 GMC Forward Control 5.7 R, AutomaticSECTION Backup Lamps Always On
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
Backup Lamps Always On
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems. |
|||
| 1 | Did you perform the Lighting System Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Lighting Systems |
| 2 |
|
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Remove the backup lamps relay. Do the backup lamps turn OFF? |
Go to Step 5 | Go to Step 4 |
| 4 | Repair a short in the backup lamps relay switched battery positive voltage supply circuit. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you complete the repair? |
Go to Step 6 | - |
| 5 | Replace the backup lamps relay. Refer to Relay Replacement (Attached to Wire Harness)
or Relay Replacement (Within an Electrical Center)
in Wiring Systems. Did you complete the replacement? |
Go to Step 6 | - |
| 6 | Operate the system in order to verify the repair. Did you correct the condition? |
System OK | Go to Step 2 |
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.