Transfer Case Shift Control Switch Indicators Flash Continuously 15 Seconds or More

Transfer Case Shift Control Switch Indicators Flash Continuously 15 Seconds or More

Circuit Description
This symptom is usually the result of actions expected to take place during the transition of a transfer case mode change, which has not happened. When the transfer case changes from 2WD to 4WD, for example, the front axle is Locked by the transfer case shift control module. If the transfer case shift control module does not sense that the front axle is applied, the module waits for the action to take place before the gear change is made. While waiting, the mode switch lamp continues to flash for a period of time, at which time all other mode requests are ignored for the duration of the ignition cycle.

The front axle control circuit consists of an electric motor actuator which engages and disengages the front axle. The front axle actuator motor consists of a permanent magnetic (PM) motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit all within the actuator assembly.

The front axle actuator consists of the following circuits:
^ The front axle control circuit, which is also connected to the transfer case shift control module
^ The front axle switch circuit, which is also connected to the transfer case shift control module
^ A battery feed circuit
^ A ground circuit

When a shift to AUTO 4WD, 4HI, or 4LO is requested, the transfer case shift control module engages the front axle by grounding the front axle control circuit through a current limiting driver.

Test Description

Steps 1-6:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines the position of the front axle switch.
3. This step helps determine if the front axle will not engage.
4. This step helps determine if the front axle will not disengage.