OPERATION

The rear axle lock indicator gives an indication to the vehicle operator when the locking mechanism in the rear axle of vehicles equipped with the optional off-road package is engaged. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Totally Integrated Power Module (TIPM) over the Controller Area Network (CAN) data bus

The rear axle lock indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED will always be OFF when the ignition switch is in any position except ON or START. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the rear axle lock indicator for the following reasons:

• Rear Axle Lock Indicator Lamp-On Message - Each time the cluster receives an electronic rear axle lock lamp-ON message from the TIPM, the indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the TIPM, or until the ignition switch is turned to the OFF position, whichever occurs first.
• Actuator Test - Each time the cluster is put through the actuator test, the rear axle lock indicator will be turned ON, then OFF again during the LED portion of the test to confirm the functionality of the LED and the cluster control circuitry.

The TIPM continually monitors an input from the rear axle lock solenoid to determine the status of the rear axle lock mechanism. The TIPM then sends the proper lamp-ON or lamp-OFF message to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN).

For proper diagnosis of the rear axle lock system, the TIPM, the EMIC, the CAN data bus or the electronic communication related to rear axle lock indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.