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

Normal Operation and Fault Conditions

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

LAST_DIR_CLCK_RT
LAST_DIR_CNTR_LEFT

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

4x4_SW
IWE_OUT_ENGAGED #

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 FOUR WHEEL DRIVE SYSTEMS for schematic and connector information.

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 are unlocked. The TCCM may engage the IWE 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 are locked. In 4A, the TCCM will apply the clutch when needed to control wheel slip.

When operating in 4H and 4L modes both IWEs and the transfer case are locked. The vehicle will bind in turns in 4H and 4L modes.

DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Condition
TCCM C1979:00	IWE Solenoid Circuit Failure: No Sub Type Information	This DTC sets when the TCCM detects there is a possible mechanical fault present with the IWE system based on wheel speed message data. When the DTC is present IWE solenoid output shall continue to operate normally.

Possible Sources

4WD system and/or related components

NOTE: 4X4 High and 4X4 Low are not intended for driving on hard/dry surfaces. Using these modes while driving on these surfaces may produce noises like intermittent clunking, but does not damage driveline components.