Differential Lock: Description and Operation

AXLE LOCK

GENERAL
For this vehicle, the Axle Lock has no dedicated module controller. A manual switch located on the instrument panel controls the system. No DTC's will occur for this system.

DESCRIPTION
The axle lock has the ability to lock the front and rear axle differentials. The system components are the instrument cluster, axle lock switch, front and rear locker relays, front and rear locker pumps, and locker indicator switches. To operate both lockers three requirements need to be met:
1. ignition in the ON position
2. transfer case range sensor indicating 4 "LOW" range
3. vehicle speed less than 16km/h (10 mph)

The 16km/h (10 mph) engagement is for engagement only All axles will remain locked if vehicle speed does not exceed 72 km/h (45 mph).

The instrument cluster has the control logic that monitors these requirements. If the requirements are not met the axle lock switch will be disabled. The axle lock switch receives the enable signals from the instrument cluster. Any subsequent down-ward press of the axle lock switch will operate the front locker relay and front locker pump. The first downward press on the axle lock switch locks the rear axle, the second downward press locks the front axle (rear is still locked), the third downward press unlocks the front axle (rear is still locked), the fourth downward press locks the front axle (rear axle is still locked). An upward press on the axle lock switch at any time will unlock any axle that is currently locked.

The enabled axle lock switch energizes the locker relay and voltage is sent to the locker pump to supply 5 psi of air to the axle allowing the differential to lock up. The "axle lock" indicator on the instrument cluster flashes during the transition state. The instrument cluster is seeking lock feedback from the locking indicator switch. With a successful lock request the "axle lock" indicator will be illuminated and a chime will sound.

If an axle is engaged the axle lock switch remains enabled until all axles are unlocked, regardless if the key is removed from the ignition switch. If the ignition key is removed and either axle is locked the instrument cluster "axle lock" indicator to the corresponding axle will flash and the chime will sound three times to alert of battery discharge. Flashing 11 axle lock" indicators will continue until axles are unlocked. Once the axles have been locked it will remain locked until one of the following happens:

1. an upward press of the axle lock switch for all locked axles or downward press for front axle only
2. transfer case is shifted out of 4 "LOW" range
3. vehicle speed exceeds 72 km/h (45 mph)
4. loss of battery power