Circuit Description
The 4WD LO circuit is used to inform the powertrain control module when the transfer case has been placed into 4WD LO mode. The powertrain control module supplies the circuit with a 12 V signal. When the transfer case is placed into 4WD LO, the transfer case shift control module pulls the 12 V signal low which is then sensed by the powertrain control module.
This DTC detects an internal module fault or a short to voltage on the 4WD LO signal circuit.
Conditions for Setting the DTC
| • | After the system turns the output on, grounding the 4WD Low Signal Circuit, and reads back a high voltage, the DTC is set. The system will not attempt it again during that ignition cycle. |
| • | The transfer case shift control module reads back a high voltage when a low voltage is expected on the 4WD LO Signal Circuit. |
Action Taken When the DTC Sets
| • | May affect the transmission shift points. |
| • | The SERVICE 4WD indicator will be 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 exits. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | History DTCs can be cleared using a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Tests the 4WD low circuit for voltage.
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Tests the 4WD low circuit for a short to voltage.
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Tests the 4WD low circuit for an open or high resistance.
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Repairs the 4WD low circuit for a short to voltage.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Transfer Case Control Connector End Views | ||||
1 | Was the Transfer Case Diagnostic System Check performed? | -- | Go to Step 2 | |
Does the DMM indicate battery voltage? | -- | Go to Step 3 | Go to Step 4 | |
Does the DMM continue to show battery voltage? | -- | Go to Step 5 | Go to Step 7 | |
Test the 4WD LO circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Was the condition found and corrected? | -- | Go to Step 8 | Go to Step 6 | |
5 | Repair the 4WD LO circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 8 | -- |
6 | Replace the powertrain control module. Refer to Powertrain Control Module Replacement 2.2L or Powertrain Control Module Replacement 4.3L. Is the replacement complete? | -- | Go to Step 8 | -- |
7 | Replace the transfer shift case control module. Refer to Transfer Case Shift Control Module Replacement . Is the replacement complete? | -- | Go to Step 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
