Pinpoint Test C: The Front Axle Does Not Engage/Disengage Correctly
Four Wheel Drive (4WD) Systems - 1-Speed Torque-On-Demand
Pinpoint Test C: The Front Axle Does Not Engage/Disengage Correctly
Refer to Wiring Diagram Set 34, Four-Wheel Drive System for schematic and connector information Electrical Diagrams.
Normal Operation
In 4X2 mode, the Transfer Case Control Module (TCCM) supplies a ground path to the Integrated Wheel End (IWE) solenoid to apply vacuum to the IWEs (Integrated Wheel Ends) (disengaging the front hubs from the front axle). In 4X4 mode and 4X4 AUTO modes, the TCCM (Transfer Case Control Module) does not supply the ground path to the IWE (Integrated Wheel End) solenoid, vacuum is not applied to the IWEs (Integrated Wheel Ends) and an internal spring keeps the hubs engaged.
- DTC C1979:11 (IWE Solenoid Circuit Failure: Circuit Short To Ground)- Fault sets when TCCM (Transfer Case Control Module) C2371A pin 6 detects a short to ground. Fault results in IWEs (Integrated Wheel Ends) hubs disengaged all the time.
- DTC C1979:12 (IWE Solenoid Circuit Failure: Circuit Short To Battery)- Fault sets when TCCM (Transfer Case Control Module) C2371A pin 6 detects a short to voltage. Fault results in IWEs (Integrated Wheel Ends) hubs engaged all the time.
- DTC C1979:13 (IWE Solenoid Circuit Failure: Circuit Open)- Fault sets when TCCM (Transfer Case Control Module) C2371A pin 6 detects an open circuit. Fault results in IWEs (Integrated Wheel Ends) hubs engaged all the time.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Vacuum leaks
- Mode Select Switch (MSS)
- IWEs (Integrated Wheel Ends)
- IWE (Integrated Wheel End) solenoid
- Transfer case
- Front axle assembly
- TCCM (Transfer Case Control Module)
PINPOINT TEST C : THE FRONT AXLE DOES NOT ENGAGE/DISENGAGE CORRECTLY
C1 CHECK FOR TCCM (Transfer Case Control Module) DTCs
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self-Test- TCCM (Transfer Case Control Module).
Are any DTCs present?
Yes
For DTC C1979:11, GO to C19.
For DTC C1979:12, GO to C18.
For DTC C1979:13, GO to C20.
For all other DTCs, REFER to the Transfer Case Control Module (TCCM) DTC Chart. Four Wheel Drive (4WD) Systems - 1-Speed Torque-on-Demand
No
GO to C2.
C2 CHECK FOR GRINDING NOISES AT HIGH SPEEDS
- With the vehicle warm and the MSS (Mode Select Switch) in 2H mode, drive the vehicle at sustained WOT (Wide Open Throttle) for 5 seconds.
Is there a grinding noise from the axle system during WOT (Wide Open Throttle)?
Yes
GO to Pinpoint Test H. Pinpoint Test H: The Front Axle Makes Noise in 2H Mode Only and Generally Under Heavy Throttle
No
GO to C3.
C3 CHECK TCCM (Transfer Case Control Module) OPERATION
- Ignition ON.
- Monitor the 4X4 indicator on the IC (Instrument Cluster) while moving the MSS (Mode Select Switch) between 2H and 4H modes.
Does the 4X4 indicator illuminate when the MSS (Mode Select Switch) is in the 4H position and turn off when the MSS (Mode Select Switch) is in the 2H position?
Yes
GO to C4.
No
GO to Pinpoint Test D. Pinpoint Test D: The Vehicle Does Not Shift Between 4X4 AUTO and 4X4 Modes Correctly
C4 CHECK THE IWE (Integrated Wheel End) DISENGAGEMENT
NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs (Integrated Wheel Ends) to engage and disengage.
- With the vehicle in NEUTRAL, position it on a hoist.
- Place the MSS (Mode Select Switch) in 2H.
- Start the engine.
- 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 either front halfshaft rotate?
Yes
GO to C8.
No
GO to C5.
C5 CHECK THE IWE (Integrated Wheel End) ENGAGEMENT
- With the engine running, place the MSS (Mode Select Switch) in 4H.
- Rotate the LF tire one revolution forward and one revolution backward while observing the LF halfshaft.
- Rotate the RF tire one revolution forward and one revolution backward while observing the RF halfshaft.
Did both front halfshafts rotate?
Yes
The front axle is operating properly at this time. CARRY OUT the 4WD (Four-Wheel Drive) Functional Test. GO to Pinpoint Test I. Pinpoint Test I: Four-Wheel Drive (4WD) System Functional Test
No
GO to C6.
C6 CHECK THE IWE (Integrated Wheel End) SOLENOID OUTPUT IN 4H
- Disconnect the output vacuum line at the IWE (Integrated Wheel End) solenoid.
- With the engine running and the MSS (Mode Select Switch) in 4H, measure the vacuum at the output port of the IWE (Integrated Wheel End) solenoid.
Is the vacuum less than 25 mm (1 in) Hg?
Yes
The IWE (Integrated Wheel End) is mechanically stuck in the disengaged position. INSTALL a new IWE (Integrated Wheel End) on the halfshaft(s) that did not rotate. REFER to Integrated Wheel End (IWE) . TEST the system for normal operation.
No
GO to C7.
C7 CHECK THE IWE (Integrated Wheel End) SOLENOID
- Ignition OFF.
- Disconnect: IWE (Integrated Wheel End) Solenoid C1157.
- Start the engine.
- With the engine running, measure the vacuum at the output port of the IWE (Integrated Wheel End) solenoid.
Is the vacuum less than 25 mm (1 in) Hg?
Yes
GO to C20.
No
INSTALL a new IWE (Integrated Wheel End) solenoid. TEST the system for normal operation.
C8 CHECK THE IWE (Integrated Wheel End) SOLENOID OUTPUT VACUUM IN 2H
- Disconnect the output vacuum line at the IWE (Integrated Wheel End) solenoid.
- With the engine running and the MSS (Mode Select Switch) in 2H, measure the vacuum at the output port of the IWE (Integrated Wheel End) solenoid.
Is the vacuum greater than 254 mm (10 in) Hg?
Yes
GO to C11.
No
GO to C9.
C9 CHECK THE IWE (Integrated Wheel End) SOLENOID INPUT VACUUM
- Disconnect the supply vacuum line at the IWE (Integrated Wheel End) solenoid.
- With the engine running, measure the supply line vacuum to the IWE (Integrated Wheel End) solenoid.
Is the vacuum greater than 254 mm (10 in) Hg?
Yes
GO to C20.
No
GO to C10.
C10 CHECK THE VACUUM RESERVOIR
- Ignition OFF.
- With the source vacuum line still disconnected, connect a vacuum pump to the vacuum port on the vacuum reservoir and apply 508 mm (20 in) Hg of vacuum.
Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute?
Yes
REPAIR or INSTALL new vacuum lines or INSTALL a check valve. TEST the system for normal operation.
No
INSTALL a new vacuum reservoir. TEST the system for normal operation.
C11 CHECK THE IWE (Integrated Wheel End) VACUUM LINES
- Ignition OFF.
- Disconnect the output vacuum line from the IWE (Integrated Wheel End) solenoid.
- Disconnect and plug the LH and RH IWE (Integrated Wheel End) vacuum lines at the IWEs (Integrated Wheel Ends).
- Connect a vacuum pump to the IWE (Integrated Wheel End) output vacuum circuit at the IWE (Integrated Wheel End) solenoid connection. Apply 508 mm (20 in) Hg of vacuum and observe the vacuum reading.
Does the vacuum drop more than 25 mm (1 in) Hg per minute?
Yes
GO to C14.
No
GO to C12.
C12 CHECK THE LH IWE (Integrated Wheel End) VACUUM LINE FOR AN OBSTRUCTION
- REMOVE the plug from the vacuum line at the LH IWE (Integrated Wheel End).
- Connect a hand vacuum pump to the LH IWE (Integrated Wheel End) vacuum line and attempt to draw a vacuum on the line.
Did the vacuum pump draw a vacuum on the LH IWE (Integrated Wheel End) vacuum line?
Yes
INSTALL a new vacuum line. CLEAR the DTCs. TEST the system for normal operation.
No
GO to C13.
C13 CHECK THE RH IWE (Integrated Wheel End) VACUUM LINE FOR AN OBSTRUCTION
- REMOVE the plug from the vacuum line at the RH IWE (Integrated Wheel End).
- Connect a vacuum pump to the RH IWE (Integrated Wheel End) vacuum line and attempt to draw a vacuum on the line.
Did the vacuum pump draw a vacuum on the RH IWE (Integrated Wheel End) vacuum line?
Yes
INSTALL a new vacuum line. CLEAR the DTCs. TEST the system for normal operation.
No
GO to C14.
C14 CHECK THE RH IWE (Integrated Wheel End) LEAK RATE
- Apply 508 mm (20 in) Hg of vacuum to the RH IWE (Integrated Wheel End) port and observe vacuum reading.
Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute?
Yes
GO to C15.
No
INSTALL a new RH IWE (Integrated Wheel End). REFER to Integrated Wheel End (IWE) . TEST the system for normal operation.
C15 CHECK THE RH IWE (Integrated Wheel End) OPERATION
- Connect a vacuum pump with gauge to the larger port of the RH IWE (Integrated Wheel End).
- Observe the RH halfshaft while rotating the RH front tire. Apply between 152 and 203 mm (6 to 8 in) Hg of vacuum and release the vacuum to manually disengage and engage the RH IWE (Integrated Wheel End).
Did the RH IWE (Integrated Wheel End) disengage between 152 and 203 mm (6 to 8 in) Hg and engage when the vacuum is released?
Yes
CONNECT the vacuum line to the RH IWE (Integrated Wheel End). GO to C16.
No
INSTALL a new RH IWE (Integrated Wheel End). REFER to Integrated Wheel End (IWE) . TEST the system for normal operation.
C16 CHECK THE LH IWE (Integrated Wheel End) LEAK RATE
- Disconnect the vacuum line from the larger port at the LH IWE (Integrated Wheel End).
- Apply 508 mm (20 in) Hg of vacuum to the LH IWE (Integrated Wheel End) port and observe vacuum reading.
Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute?
Yes
GO to C17.
No
INSTALL a new LH IWE (Integrated Wheel End). REFER to Integrated Wheel End (IWE) . TEST the system for normal operation.
C17 CHECK THE LH IWE (Integrated Wheel End) OPERATION
- Connect a vacuum pump with gauge to the larger port of the LH IWE (Integrated Wheel End).
- Observe the LH halfshaft while rotating the LH front tire. Apply between 152 and 203 mm (6 to 8 in) Hg of vacuum and release the vacuum to manually disengage and engage the LH IWE (Integrated Wheel End).
Did the LH IWE (Integrated Wheel End) disengage between 152 and 203 mm (6 to 8 in) Hg and engage when the vacuum is released?
Yes
CONNECT the vacuum line to the LH IWE (Integrated Wheel End). GO to C18.
No
INSTALL a new LH IWE (Integrated Wheel End). REFER to Integrated Wheel End (IWE) . CLEAR the DTCs. TEST the system for normal operation.
C18 CHECK THE IWE (Integrated Wheel End) SOLENOID CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: IWE (Integrated Wheel End) Solenoid C1157.
- Disconnect: TCCM (Transfer Case Control Module) C2371A.
- Ignition ON.
- Measure the voltage between IWE (Integrated Wheel End) solenoid C1157-2, circuit CCF05 (BN/BU), harness side and ground.
Is any voltage present?
Yes
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation.
No
GO to C19.
C19 CHECK THE IWE (Integrated Wheel End) SOLENOID CONTROL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: IWE (Integrated Wheel End) Solenoid C1157.
- Disconnect: TCCM (Transfer Case Control Module) C2371A.
- Measure the resistance between solenoid C1157-2, circuit CCF05 (BN/BU), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to C20.
No
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation.
C20 CHECK THE IWE (Integrated Wheel End) SOLENOID RESISTANCE
NOTE: If the temperatures (either ambient or in the engine compartment) are exceptionally high, a higher than normal resistance reading could result. A lower temperature could result in a lower resistance reading.
- Ignition OFF.
- Disconnect: IWE (Integrated Wheel End) Solenoid C1157.
- Measure the resistance between IWE (Integrated Wheel End) solenoid C1157 pins 1 and 2, component side.
Is the resistance between 44 and 70 ohms?
Yes
GO to C21.
No
INSTALL a new IWE (Integrated Wheel End) solenoid. CLEAR the DTCs. TEST the system for normal operation.
C21 CHECK FOR VOLTAGE TO THE IWE (Integrated Wheel End) SOLENOID
- Measure the voltage between IWE (Integrated Wheel End) solenoid C1157-1, circuit SBB29 (GY/RD), harness side and ground.
Is the voltage greater than 11 volts?
Yes
GO to C22.
No
CHECK Battery Junction Box (BJB) fuse 29 (20A). If OK, REPAIR circuit SBB29 (GY/RD). If not OK, REFER to the Wiring Diagrams to identify possible causes of the circuit short Electrical Diagrams. CLEAR the DTCs. TEST the system for normal operation.
C22 CHECK THE IWE (Integrated Wheel End) SOLENOID CONTROL CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: TCCM (Transfer Case Control Module) C2371A.
- Measure the resistance between IWE (Integrated Wheel End) solenoid C1157-2, circuit CCF05 (BN/BU), harness side and TCCM (Transfer Case Control Module) C2371A-6, circuit CCF05 (BN/BU), harness side.
Is the resistance less than 3 ohms?
Yes
GO to C23.
No
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation.
C23 CHECK FOR CORRECT TCCM (Transfer Case Control Module) OPERATION
- Ignition OFF.
- Disconnect all TCCM (Transfer Case Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all TCCM (Transfer Case Control Module) connectors and make sure they are seated correctly.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new TCCM (Transfer Case Control Module). REFER to 4X4 Control Module . TEST the system for normal operation.
No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. ADDRESS the root cause of the connector or pin issues.