Pinpoint Test A : Four-Wheel Drive (4WD) System Functional Test: Notes

Locator views for the vacuum lines and vacuum reservoir are located in Description and Operation. REFER to: Four-Wheel Drive Systems - System Operation and Component Description . Refer to Wiring Diagram Four Wheel Drive Systems for schematic and connector information.

Normal Operation 

The four wheel drive system functional test will isolate and test each sub-system to determine if the subsystem is functioning properly. If a fault is found, additional testing of the suspect subsystem will be required.

When operating in 2H mode, the transfer case clutch is de-energized and both IWE's are unlocked. The TCCM may engage the IWE's in 2H mode to speed warm up of the front axle fluid. The transfer case has certain amount of clutch drag which can cause the front driveshaft to spin in 2H mode.

When operating in 4WD modes both IWE's are locked. In 4A, the TCCM will apply the clutch when needed to control wheel slip.

The following parameters may be monitored in datalogger during this test: