• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
The 4WD low circuit is used to notify the powertrain control module (PCM) that the vehicle is in 4WD low range. The PCM supplies 12 volts to this circuit. The transfer case shift control module grounds this circuit when the vehicle is in 4WD low range.
This DTC detects a short-to-ground, short-to-voltage, or an open in the 4WD low circuit.
• | The ignition is ON. |
• | The system voltage is 9-18 volts. |
• | After the transfer case shift control module grounds the output, the 4WD low circuit, and reads back a high voltage, the DTC is set. The system will not attempt setting the DTC 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 low circuit. |
• | The transmission shift points may be affected. |
• | The SERVICE 4WD indicator will be latched on for the remainder of the current ignition cycle. |
• | The transfer case shift control module will clear the DTC if the condition for setting the DTC is not currently present. |
• | A history DTC will clear after 33 consecutive ignition cycles without a fault present. |
• | History DTCs can be cleared using a scan tool. |
Transfer Case Control Schematics
Transfer Case Description and Operation
Control Module References for scan tool information.
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.