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 693 (CELLULAR COMMUNICATION SYSTEM)
1999 GMC Forward Control 5.7 R, Automatic
Section 693 (Cellular Communication System)
1999 GMC Forward Control 5.7 R, AutomaticSECTION Section 693 (Cellular Communication System)
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
- Specifications
- Schematic and Routing Diagrams
- Component Locator
- Diagnostic Information and Procedures
- Diagnostic Starting Point - Cellular Communication
- Diagnostic System Check - Cellular Communication
- Scan Tool Data List
- Scan Tool Data Definitions
- Diagnostic Trouble Code (DTC) List
- DTC B2462
- DTC B2476
- DTC U1500
- OnStar Symptom Diagnosis
- Symptoms - Cellular Communication
- OnStar Always On
- OnStar One or More Buttons Inoperative
- OnStar Cannot Control Horns, Door Unlock, or Exterior Lamps
- Unable to Contact OnStar Call Center
- OnStar Call Center Unable to Configure OnStar (R) System
- Microphone Inoperative - Caller Cannot Be Heard
- Voice Recognition Inoperative
- OnStar Button LED Inoperative
- No (or Noisy) OnStar Audio
- Global Positioning System (GPS) Data Not Current or Inaccurate
- OnStar Battery Consumption Test
- OnStar Reprogramming
- Repair Instructions
- Description and Operation
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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.