Test Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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.
- 2: Tests for an intermittent condition.
- 3: Determines whether the failure is the result of a faulty 4WD system.
- 4: Determines if the failure is the result of a faulty instrument cluster.
- 5: Determines if the failure is the result of a faulty PCM.
4WD Indicator Always On
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Transfer Case Control Schematics | ||||
| 1 | Did you perform A Diagnostic System Check - Transfer Case? | - | Go to Step 2 | Go to Diagnostic System Check - Transfer Case |
| 2 | Verify the fault is present. Does the system operate normally? |
- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Does the front axle disengage when the four wheel drive (4WD) control lever is in the two wheel drive (2WD) position? | - | Go to Step 4 | Go to Four-Wheel Drive Does Not Disengage |
| 4 |
|
- | Go to Step 5 | Go to Step 8 |
| 5 | Test the axle switch signal circuit for voltage at the PCM. Does the voltage measure within the specified value? |
9-14V | Go to Step 6 | Go to Step 7 |
| 6 | Inspect the axle switch signal circuit for a short to voltage. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. If OK, replace the front axle actuator. Refer to Electric Motor Actuator Replacement
in Front Drive Axle. Did you complete the replacement? |
- | Go to Step 9 | - |
| 7 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement
in Engine Controls - 4.3 L, Powertrain Control Module (PCM) Replacement
in Engine Controls - 4.8 L, 5.3 L, and 6.0 L, or Powertrain Control Module (PCM) Replacement
in Engine Controls - 8.1 L. Did you complete the replacement? |
- | Go to Step 9 | - |
| 8 | Replace the instrument panel cluster. Refer to Instrument Panel Cluster (IPC) Replacement
in Instrument Panel, Gauges, and Console. Did you complete the replacement? |
- | Go to Step 9 | - |
| 9 | Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? |
- | System OK | Go to Step 2 |