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 836 (CELLULAR COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESONSTAR BUTTON LED INOPERATIVETEST DESCRIPTION
1999 GMC Forward Control 5.7 R, Automatic
Test Description
1999 GMC Forward Control 5.7 R, AutomaticSECTION Test Description
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers on the diagnostic table.
- 3: Determines if the OnStar® status LED has the necessary GREEN LED signal circuit voltage.
- 5: If the GREEN LED signal is shorted to voltage then the OnStar® 3-button assembly has been damaged and the OnStar® 3-button assembly must be replaced.
OnStar Button LED Inoperative
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: OnStar Schematics Connector End View Reference: Cellular Communication Connector End Views DEFINITION: This procedure is for diagnosing problems with the OnStar® button assembly LED. |
||||
| 1 | Did you perform the Cellular Communications Diagnostic System Check? | - | Go to Step 2 | Go to Diagnostic System Check - Cellular Communication |
| 2 |
|
- | Go to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems | Go to Step 3 |
| 3 | Measure the voltage from the keypad GREEN LED signal circuit to a good ground. Does the voltage measure near the specified value? |
7 V | Go to Step 6 | Go to Step 4 |
| 4 | Test the keypad GREEN LED signal circuit for an open, high resistance or a short to ground. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 10 | Go to Step 5 |
| 5 | Test the keypad GREEN LED signal circuit for a short to voltage. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 7 | Go to Step 8 |
| 6 | Inspect for poor connections at the harness connector of the rearview mirror. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 10 | Go to Step 7 |
| 7 | Replace the rearview mirror. Refer to Rearview Mirror Replacement
in Stationary Windows. Did you complete the repair? |
- | Go to Step 10 | - |
| 8 | Inspect for poor connections at the harness connector of the vehicle communication interface module (VCIM). Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 10 | Go to Step 9 |
| 9 |
IMPORTANT:
Perform the OnStar® setup procedure. Replace the VCIM. Refer to Communication Interface Module Replacement .Did you complete the repair? |
- | Go to Step 10 | - |
| 10 | Operate the system in order to verify the repair. Did you correct the condition? |
- | System OK | Go to Step 2 |
RENDER: 1.0x
NO RELATED
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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.