Circuit Description
The 4WD indicator lamp is located in the instrument panel cluster (IPC). Ignition 1 voltage is supplied to the IPC when the ignition switch is in the START or RUN position. When the vehicle is in START or RUN and the powertrain control module (PCM) receives the axle switch signal from the front axle actuator, the PCM sends a class 2 signal to the IPC, turning on the 4WD indicator. The 4WD indicator stays on as long as the axle switch signal input is present.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests for an intermittent condition.
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This step determines whether the condition is the result of a faulty 4WD system.
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This step determines if the condition is the result of a faulty IPC.
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This step determines if the condition is the result of a faulty PCM.
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 | |
Verify the condition is present. Does the system operate normally? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 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 | ||
Does the 4WD indicator turn OFF when all indicators are turned OFF? | -- | Go to Step 5 | Go to Step 8 | |
Test the axle switch signal circuit for voltage at the PCM. Does the voltage measure within the specified value? | 9-14 V | 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 Replacement in Engine Controls - 4.3L, Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L, or Powertrain Control Module Replacement in Engine Controls - 8.1L. Did you complete the replacement? | -- | Go to Step 9 | -- |
8 | Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges, and Console. Did you complete the replacement? | -- | Go to Step 9 | -- |
9 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 |
