The indicator lamps circuit consist of five individual lamps contained inside the mode/range switch assembly. They are AUTO 4WD, 2HI, 4HI, 4LO and NEUTRAL. The AUTO 4WD, 2HI, 4HI, and 4LO lamps are contained inside their respective range button. When the ignition in ON, the transfer case shift control module illuminates the indicator lamp that corresponds to the current ATC gear position by providing a ground through a current limiting driver.
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 completes the shift.
A solid state circuit located inside the switch supplies ignition voltage to the lamps. The solid state circuit also receives voltage when the headlamp switch is in the parklamp or headlamp position. When the solid state circuit receives voltage from the headlamp switch, it reduces the voltage that it supplies to the indicator lamps, dimming the lamps when the headlamps are ON.
The numbers below refer to the step numbers on the diagnostic table.
This step tests the transfer case electrical control of the lamp circuits.
This step helps determine module failures.
This step tests the affected lamp circuit for an open or high resistance.
This step tests the lamp feed circuit for an open or short to ground.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Transfer Case Control Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Transfer Case? | Go to Step 2 | |
Do all the indicators illuminate? | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
Important: Do not damage a connector or circuit while back probing.
Does the affected lamp turn ON? | Go to Step 4 | Go to Step 5 | |
Test the affected indicator control circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 7 | |
Test the LED dimming supply circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 6 | |
6 | Replace the transfer case shift control switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | Go to Step 8 | -- |
7 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement . Did you complete the repair? | Go to Step 8 | -- |
8 |
Does the symptom occur? | Go to Step 2 | System OK |