• | 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 either the powertrain control module (PCM) for gasoline applications or the engine control module (ECM) for diesel applications that the vehicle is in 4WD low range. The applicable control module 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 for 5 seconds. |
• | The transfer case shift control module reads back a high voltage when a low voltage is expected on the 4WD low circuit. |
• | Transmission shift points may be affected. |
• | The SERVICE 4WD indicator is not illuminated. |
• | 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 100 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.