Circuit Description
The front axle control circuit consists of a Front Drive Axle Clutch solenoid which is electronically controlled by the transfer case shift control module. This solenoid opens and closes a vacuum control valve allowing vacuum to apply and release a clutch pack inside the front axle housing. The transfer case shift control module determines whether or not the clutch pack has been applied or released based on a signal form the front axle switch mounted on the front axle housing assembly. The front axle is normally locked or engaged during AUTO 4WD, 4WD HI, and 4WD LO modes. The front axle is unlocked or disengaged only during 2 HI or neutral modes.
Conditions for Setting the DTC
| • | The system will try to engage the front axle. If it can not engage the front axle, the system will not attempt it again during that ignition cycle. |
| • | The transfer case shift control module reads back the front axle output as a high voltage when a low voltage is expected. |
Action Taken When the DTC Sets
| • | All shifting for 4WD, AUTO 4WD, and 4WD LO modes will be disabled. |
| • | SERVICE indicator (4WD/AWD) lamp will be latched on for the remainder of the current ignition cycle. |
Conditions for Clearing the DTC
| • | The Transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists. |
| • | A history DTC will clear after 100 consecutive ignition cycle without a fault present. |
| • | History DTCs can be cleared using a scan tool. |
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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Tests the operation of the front axle switch.
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Tests the front axle control circuit for a short to voltage.
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Helps determine whether the short to voltage is due to a faulty transfer case shift control module or wiring.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Transfer Case Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check |
Does the Front Axle Switch status change with each command? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | |
Did you find a short to voltage? | -- | Go to Step 4 | Go to Step 5 | |
Was the condition found and corrected? | -- | Go to Step 7 | Go to Step 6 | |
5 | Replace the front axle actuator. Refer to Front Drive Axle Actuator Replacement in Front Axle. Did you complete the replacement? | -- | Go to Step 7 | -- |
6 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement . Did you complete the replacement? | -- | Go to Step 7 | -- |
7 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
