If you receive customer reports on an applied vehicle of the low- range light flashing rapidly (18 times) after vehicle start with fault code P1831 (Positioner motor, position sensor or power supply is faulty) in the transfer case ECU, do not replace the transfer case motor. This is caused by temporary loss of communication between the transfer case control module and the shift motor position sensor.
174/175, as of Chassis # A346835.
To resolve, read out the fault codes and cycle the transfer case shift motor by following the below procedure.
1. Read out and erase the fault codes.
2. If fault codes other than P1831 are present, diagnose and repair accordingly (use appropriate damage code, operation code and time).
3. If fault code P1831 is present, start the vehicle.
4. Shift the transmission into neutral (N).
5. Push the LOW RANGE switch. Depress the brake pedal.
6. After the shift motor has cycled, push the LOW RANGE switch again. The LOW RANGE light should go out at this time.
7. Confirm proper transfer case shift function: Cycle ignition and repeat steps 2-5.
Warning: While performing the transfer case shift adaptation described above, take all necessary safety measures, such as applying the parking brake and firmly holding the service brake. (Failure to do so can result in unintended vehicle movement.)
Courtesy of IDENTIFIX.