Rear Lock Indicator: Operation

The rear lock indicator gives an indication to the vehicle operator of the status of the locker mechanism in the rear axle of vehicles equipped with the optional off-road package. The rear lock indicator can also give an indication when certain faults are detected in the axle locker system. This indicator is controlled by a transistor on the instrument cluster electronic circuit board based upon cluster programming, and hard wired inputs to the cluster from the key-in ignition switch, the axle lock switch, and the rear locker indicator switch. The rear lock indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will allow this indicator to operate whenever the instrument cluster receives a battery current input on the fused B(+) circuit. Therefore, the LED can be illuminated regardless of the ignition switch position. The cluster can illuminate the LED solid, or flash it on and off at two different rates, slow or fast. The slow rate is about one flash per second, while the fast rate is about two flashes per second. 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 lock indicator for the following reasons:

• Rear Axle Lock Request Input  - Each time the cluster detects ground on the rear axle lock request circuit from the axle lock switch (rear axle lock request circuit ground = rear axle lock request active) while the key is in the ignition lock cylinder, the rear lock indicator flashes on and off at a slow rate. The indicator continues to flash until the rear axle lock request input to the cluster is an open circuit (rear axle lock request circuit open = rear axle lock request inactive), or until the cluster detects a change in the inputs from the rear locker indicator switch or the key-in ignition switch, whichever occurs first.
• Rear Locker Indicator Switch Input  - Each time the cluster detects ground on the rear locker indicator switch sense circuit (rear locker indicator switch closed = rear axle locker engaged) while the rear axle lock request is active and the key is in the ignition lock cylinder, the rear lock indicator is illuminated solid. The indicator remains illuminated solid until the rear locker indicator switch input to the cluster is an open circuit (rear locker indicator switch open = rear axle locker disengaged), or until the cluster detects a change in the inputs from the axle lock switch or the key-in ignition switch, whichever occurs first.
• Rear Lock Request/Feedback Mismatch  - Each time the cluster detects that the inputs from the axle lock switch (request) on the rear axle lock request circuit and from the rear locker indicator switch (feedback) on the rear locker indicator switch sense circuit are mismatched, the rear lock indicator flashes on and off at a slow rate. This condition occurs when the lock request is active but the axle locker remains disengaged, or when the lock request is inactive but the axle locker remains engaged. The indicator continues to flash until the request and the feedback are matching.
• Key-In Ignition Switch Input  - Each time the cluster detects that the key has been removed from the ignition lock cylinder (key-in ignition switch open = key is not in ignition switch) while the rear axle lock request is still active, the rear lock indicator flashes at a fast rate and three chime tones are sounded. The indicator will continue to flash at this rate until the key is replaced in the ignition switch lock cylinder (key-in ignition switch closed = key is in ignition switch) while the rear axle lock request is still active, or until the rear axle lock request input is deactivated, whichever occurs first.

The axle lock switch in the accessory switch bezel on the instrument panel provides a hard wired ground input to the instrument cluster circuitry through the rear axle lock request circuit whenever the switch is enabled and the rear or the rear and front axle lock position of the switch is selected by the vehicle operator. The rear locker indicator switch on the rear axle housing provides a hard wired ground input to the instrument cluster whenever the rear axle locker mechanism is engaged. The key-in ignition switch integral to the ignition switch provides a hard wired ground input to the instrument cluster whenever a key is present in the ignition lock cylinder. Each of these inputs to the instrument cluster can be diagnosed using conventional diagnostic tools and methods. For further diagnosis of the instrument cluster circuitry that controls the rear lock indicator LED, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING  ).