The 4WD indicator lamp is located in the instrument cluster. Ignition 3 voltage is supplied to the instrument panel cluster (IPC) when the ignition switch is in the START or RUN position. When the vehicle is in START or RUN and the Engine control module (ECM) receives the axle switch signal from the front axle actuator, the ECM sends a CAN signal to the instrument cluster turning on the 4WD indicator. The 4WD indicator will stay on as long as the axle switch signal input is present.

Schematic Reference

Transfer Case Control Schematics

Connector End View Reference

Transfer Case Control Connector End Views

Electrical Information Reference

1. Place the vehicle in 4WD install a scan tool and using engine data 2 look at the display for 4WD signal.
2. Verify that the scan tool indicates that the vehicle is in 4WD.

⇒	If the scan tool indicates that the vehicle is in 2WD go to circuit system testing.

1. Check the axle switch signal circuit for an open or high resistance.

⇒	If everything checks normal then go to the next step.

2. Check the front axle actuator control circuit pin B at the front axle actuator connector or pin C at the transfer case shift control switch for an open or high resistance.

⇒

If everything checks normal then short the axle actuator control circuit to ground this should cause the actuator to engage. Remove the short to ground and then short the circuit to ground again, this should cause the actuator to disengage. If the actuator does not operate properly then refer to front axle will not engage or front axle will not disengage. If everything checks normal go to ECM and IPC functionality check.

If all circuits referenced above check good use the scan tool under engine data 2 to see if the scan tool still indicates the vehicle is still in 2WD.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.