The 4WD LO Circuit is used to notify the vehicle control module (VCM)/powertrain control module (PCM) that the vehicle is in 4WD low range. VCM/PCM supplies 12 V to this circuit. The transfer case shift control module grounds this circuit when the vehicle is in 4WD low range.
This DTC detects an transfer case shift control module problem, a short to voltage on the 4WD LO Circuit.
• | After the transfer case shift control module grounds the 4WD LO 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 4 LO Circuit. |
• | May affect the transmission shift points. |
• | The SERVICE indicator (AWD/4WD) lamp 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 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. |
The numbers below refer to the step numbers on the diagnostic table.
Tests the 4WD LO circuit for voltage.
Tests the 4WD LO circuit for a short to voltage.
Tests the 4WD LO circuit for an open or high resistance.
Repairs the 4WD LO circuit for a short to voltage.
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 DMM indicate battery voltage? | -- | Go to Step 3 | Go to Step 4 | |
Does the DMM continue to display 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 VCM Replacement/Programming for the 5.0, 5.7L engine, Powertrain Control Module Replacement/Programming for the 6.5L engine, or VCM Replacement/Programming for the 7.4L engine. 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 |