Transfer Case Shift Control Switch Indicator Flashes, Then Returns to Previous Mode
Transfer Case Shift Control Switch Indicator Flashes, then Returns to Previous ModeTest 1-8:
Circuit Description
The transfer case shift control module flashes each indicator lamp after a shift has been requested and continues to flash until the transfer case shift control module can complete the shift. If the transfer case is unable to make a shift, the requested mode indicator flashes and returns to the previous mode. If the requested mode indicator flashes for 15 seconds and returns to the previous mode, this indicates the loss of a necessary input from another module. The transfer case shift control module requires a vehicle speed sensor (VSS) signal, provided by the ABS module, and a PRNDL input provided by the transmission. These signals are provided to the transfer case shift control module via class 2, and if not received the transfer case will not shift.
If a new mode is requested and the requested mode indicator flashes less then 15 seconds and returns to the previous mode, this indicates a transfer case fault. This symptom is caused by an internal mechanical transfer case fault causing the shift detent lever shaft to bind, or a fault within the encoder motor.
Test Description
The numbers refer to the step numbers on the diagnostic table.
2. This step tests for the possibility of a missing system input or a system fault.
3. This step tests for a missing PRNDL input from the transmission.
4. This step tests for a missing VSS signal from the ABS system.
5. This step determines if the condition is caused by a faulty encoder motor or a mechanical internal fault to the transfer case.