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

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

1. Normal Operation and Fault Conditions 

   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.

   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 

   • ATCM
   • Front axle
   • Transfer case torque on demand clutch

2. A1 CHECK MODULES FOR ON DEMAND DTC (DIAGNOSTIC TROUBLE CODE)
   
   
   • Ignition ON.
   • Gear selector in Park
   • Enter the following diagnostic mode: TCCM and ATCM on demand self-test.

   Is any DTC retrieved? 

   Yes	REFER to Diagnostic Trouble Code (DTC) Chart .

   No

   GO to  A2

3. A2 CHECK ROTARY SWITCH
   
   
   NOTE: For vehicles not equipped with a rotary drive mode switch, go to  A3.
   • Gear selector in Park
   • Start engine
   • Access the ATCM and monitor the LAST_DIR_CLCK_RTPID and

     Access the ATCM and monitor the LAST_DIR_CNTR_LFTPID while rotating the ATCM rotary switch clockwise and counterclockwise

   Do LAST_DIR_CLCK_RT () and LAST_DIR_CNTR_LFT () correctly indicate the last direction the rotary knob was rotated? 

   Yes

   GO to  A3

   No	INSTALL a new ATCM. REFER to: All Terrain Control Module (ATCM) .

4. A3 CHECK SWITCH INPUT TO THE TCCM (TRANSFER CASE CONTROL MODULE) IN 2H
   
   
   • NORMAL drive mode
   • Gear selector in Park
   • Engine running
   • Access the TCCM and monitor the 4X4_SWPID

   Does the 4x4_SW display Two Wheel Drive? 

   Yes	The TCCM recognizes a valid input from the ATCM. GO to  A4

   No	INSTALL a new ATCM. REFER to: All Terrain Control Module (ATCM) .

5. A4 CHECK THE IWE (INTEGRATED WHEEL END) DISENGAGEMENT
   
   
   NOTE: The TCCM may command the IWE to engage during 2H operation to warm up the front axle.
   • With the vehicle in N, position it on a hoist. Raise the vehicle until all 4 wheels are off the ground. REFER to: Jacking and Lifting .
   • Engine Running: 
     • The engine must idle for up to 5 minutes for the vacuum on demand system to build up the vacuum required for the IWE to disengage.
     • Allow engine to idle for 5 minutes

   • Gear selector in Neutral.
   • NORMAL drive mode.
   • Access the TCCM and control the IWE_OUT_ENGAGEDPID to No (False)
   • Rotate the RH front tire one revolution forward and one revolution backward while observing the RH front halfshaft.
   • Rotate the LH front tire one revolution forward and one revolution backward while observing the RH front halfshaft.

   Did both front halfshafts remain stationary? 

   Yes	End Output State Control. GO to  A5

   No	End Output State Control.GO to Pinpoint Test I

6. A5 CHECK THE IWE (INTEGRATED WHEEL END) ENGAGEMENT
   
   
   • Vehicle on hoist with all 4 wheels off the ground.
   • Engine running.
   • Gear selector in Neutral.
   • SAND drive mode or select 4A.
   • Rotate the LH front tire one revolution forward and one revolution backward while observing the LH front halfshaft.
   • Rotate the RH front tire one revolution forward and one revolution backward while observing the RH front halfshaft

   Did both front halfshafts rotate? 

   Yes	The front axle is operating properly at this time. GO to  A6

   No	GO to Pinpoint Test I

7. A6 CHECK TORQUE ON DEMAND CLUTCH OPERATION
   
   
   • SAND drive mode or select 4H.
   • Drive the vehicle on a dry, hard surface while full lock turns.

   Is wind-up / vehicle bind present? 

   Yes	The TOD clutch is transmitting torque as expected GO to  A7

   No	The TOD clutch is slipping / not transferring torque. CHECK the transfer case. REFER to: Transfer Case - Vehicles With: 1-Speed Torque On Demand Transfer Case .

8. A7 CHECK FOR WIND-UP IN 2H MODE WITH IWE (INTEGRATED WHEEL END) ENGAGED
   
   
   • NORMAL drive Mode.
   • Access the TCCM and control the IWE_OUT_ENGAGEDPID

     # to Yes (True).

   • Drive the vehicle on a dry, hard surface while full lock turns.

   Is wind-up / vehicle bind present? 

   Yes	Exit Output State Control. The transfer case is unable to disengage 4x4. REFER to: Transfer Case - Vehicles With: 1-Speed Torque On Demand Transfer Case .

   No	Exit Output State Control. The 4WD system is operating as designed.