Pinpoint Test E: The Front Axle Does Not Engage/Disengage Correctly
Four Wheel Drive (4WD) Systems - Mechanical Shift
Pinpoint Tests
Pinpoint Test E: The Front Axle Does Not Engage/Disengage Correctly
Refer to Wiring Diagram Set 34, Four-Wheel Drive Systems for schematic and connector information. Diagrams By Number
Normal Operation
In 2H mode, the Transfer Case Control Module (TCCM) supplies a ground path to the Integrated Wheel End (IWE) solenoid to apply vacuum to the IWEs (disengaging the front hubs from the front axle). In 4H or 4L modes, the TCCM does not supply the ground path to the IWE solenoid, vacuum is not applied to the IWEs and an internal spring in the IWEs keeps the hubs engaged.
- DTC C1979:11 ( IWE Solenoid Circuit Failure: Circuit Short To Ground) - Fault sets when TCCM C2371A pin 6 detects a short to ground. Fault results in IWEs hubs disengaged all the time.
- DTC C1979:12 ( IWE Solenoid Circuit Failure: Circuit Short To Battery) - Fault sets when TCCM C2371A pin 6 detects a short to voltage. Fault results in IWEs hubs engaged all the time.
- DTC C1979:13 ( IWE Solenoid Circuit Failure: Circuit Open) - Fault sets when TCCM C2371A pin 6 detects an open circuit. Fault results in IWEs hubs engaged all the time.
This pinpoint test is intended to diagnose the following:
- Fuses
- Wiring, terminals or connectors
- Vacuum leaks
- Mode Indication Switch (MIS)
- IWEs
- IWE solenoid
- Transfer case
- Front axle assembly
- TCCM
PINPOINT TEST E: THE FRONT AXLE DOES NOT ENGAGE/DISENGAGE CORRECTLY
WARNING: When directed to drive the vehicle as part of this test, drive the vehicle on a hard surface in an area without traffic to prevent a crash. Failure to follow these instructions may result in personal injury.
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E1 CHECK FOR DTCs
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self Test - TCCM.
- Are any DTCs present?
Yes
For DTC C1979:11, GO to E20.
For DTC C1979:12, GO to E19.
For DTC C1979:13, GO to E16.
For all other DTCs, REFER to the Transfer Case Control Module (TCCM) DTC Chart. Four Wheel Drive (4WD) Systems
No
GO to E2.
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E2 CHECK FOR GRINDING NOISES AT SPEEDS
- Shift the transfer case from 2H to 4H at rest. Drive the vehicle.
- Shift the transfer case from 2H to 4H while driving the vehicle at low speed 16 km/h (10 mph).
- Shift the transfer case from 2H to 4H while driving the vehicle at high speed 64 km/h (40 mph).
- Is the axle system fully functional at rest, but there is a grinding noise during engagement, especially at high speed?
Yes
If the concern is excessive front axle noise during Four-Wheel Drive (4WD) engagement (especially at high speeds), REFER to Front Drive Axle/Differential Testing and Inspection for further diagnosis.
No
GO to E3.
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E3 CHECK THE TRANSFER CASE SHIFT TO 2H MONITORING THE TRANSFER CASE CONTACT PLATE SWITCH B (PLATE_B) AND C (PLATE_C) PIDs
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- Monitor the TCCM PLATE_B and PLATE_C PIDs while shifting the transfer case to 2H.
- Do the PLATE_B and PLATE_C PIDs indicate that the vehicle shifted into 2H?
Yes
GO to E4.
No
GO to Pinpoint Test C. Pinpoint Test C: The Vehicle Does Not Shift Between 2H (4X2) and 4H (4X4 HIGH) Correctly
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E4 CHECK THE IWE DISENGAGEMENT
- With the vehicle in NEUTRAL, position it on a hoist. Refer to Jacking and Lifting Service and Repair.
- Lift and support the vehicle off the ground until the front wheels can be spun freely. Refer to Jacking and Lifting Service and Repair.
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- 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 E10.
No
GO to E5.
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E5 CHECK THE TRANSFER CASE SHIFT INTO 4H MONITORING THE TRANSFER CASE CONTACT PLATE SWITCH B (PLATE_B) AND C (PLATE_C) PIDs
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- Monitor the PLATE_B and PLATE_C PIDs while shifting the transfer case into 4H.
- Do the PLATE_B and PLATE_C PIDs and Instrument Panel Cluster (IPC) message center indicate that the transfer case shifted into 4H (4X4 HIGH)?
Yes
GO to E6.
No
GO to Pinpoint Test C. Pinpoint Test C: The Vehicle Does Not Shift Between 2H (4X2) and 4H (4X4 HIGH) Correctly
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E6 CHECK THE IWE ENGAGEMENT
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- With the engine still running, 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
CHECK that all driveline fasteners are present and tightened to specification. REFER to Driveline System - General Information Specifications for further diagnosis of the front axle.
No
GO to E7.
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E7 CHECK THE IWE SOLENOID OUTPUT IN 4H
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- With the engine still running, disconnect the output vacuum line at the IWE solenoid.
- Measure the vacuum at the output port of the IWE solenoid.
- Is the vacuum less than 25 mm (1 in) Hg?
Yes
GO to E28.
No
GO to E8.
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E8 CHECK THE INTEGRATED WHEEL END OUTPUT CONTROL (IWE_OS) COMMAND IN 4H WITH THE SCAN TOOL
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- With the engine still running, use the scan tool to command IWE_OS to engage the IWEs (PID status Yes).
- Measure the vacuum at the output port of the IWE solenoid.
- Is the vacuum less than 25 mm (1 in) Hg?
Yes
END the active command. GO to E22.
No
GO to E9.
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E9 CHECK THE IWE SOLENOID
- Disconnect: IWE Solenoid C1291.
- Measure the vacuum at the output port of the IWE solenoid.
- Is the vacuum less than 25 mm (1 in) Hg?
Yes
GO to E20.
No
INSTALL a new IWE solenoid. TEST the system for normal operation.
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E10 CHECK THE IWE SOLENOID OUTPUT VACUUM IN 2H
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- With the engine still running, disconnect the output vacuum line at the IWE solenoid while having the vacuum supply attached to the solenoid.
- Shift the transfer case to the 2H position.
- Measure the vacuum at the output port of the IWE solenoid.
- Is the vacuum greater than 254 mm (10 in) Hg?
Yes
GO to E23.
No
GO to E11.
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E11 CHECK THE IWE SOLENOID INPUT VACUUM
- Disconnect the supply vacuum line at the IWE solenoid.
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- With the engine still running, measure the supply line vacuum to the IWE solenoid.
- Is the vacuum greater than 254 mm (10 in) Hg?
Yes
GO to E15.
No
GO to E12.
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E12 CHECK SOURCE VACUUM TO THE VACUUM RESERVOIR
- Disconnect the source vacuum line from the vacuum reservoir.
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- With the engine still running, measure the source vacuum being supplied to the vacuum reservoir.
- Is the vacuum greater than 254 mm (10 in) Hg?
Yes
GO to E13.
No
REPAIR or INSTALL a new source vacuum line. TEST the system for normal operation.
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E13 CHECK THE VACUUM RESERVOIR
- Ignition OFF.
- Disconnect the vacuum line from the vacuum reservoir.
- Connect a vacuum pump to the source 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
GO to E14.
No
INSTALL a new vacuum reservoir. TEST the system for normal operation.
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E14 CHECK THE VACUUM CHECK VALVE
- NOTE: The check valve is between the vacuum source and the reservoir.
- Connect the vacuum lines to the IWE solenoid.
- Connect a vacuum pump to the IWE solenoid vacuum line at 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
Concern not present at this time. CARRY OUT the Mechanical Shift-On-The-Fly (MSOF) Functional Test. GO to Pinpoint Test J. Pinpoint Test J: Mechanical Shift-On-The-Fly (MSOF) Functional Test
No
REPAIR or INSTALL new vacuum lines or INSTALL a check valve. TEST the system for normal operation.
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E15 CHECK THE INTEGRATED WHEEL END OUTPUT CONTROL (IWE_OS) COMMAND IN 2H WITH THE SCAN TOOL
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- With the engine still running, use the scan tool to command IWE_OS to disengage the IWEs (PID status No).
- Measure the vacuum at the output port of the IWE solenoid.
- Is the vacuum greater than 254 mm (10 in) Hg?
Yes
GO to E22.
No
END the active command. GO to E16.
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E16 CHECK FOR VOLTAGE TO IWE SOLENOID
- Ignition OFF.
- Disconnect: IWE Solenoid C1291.
- Measure the voltage between IWE solenoid C1291-1, circuit SBB29 (GY/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to E17.
No
VERIFY Battery Junction Box (BJB) fuse 29 (10A) is OK. If OK, REPAIR circuit SBB29 (GY/RD) for an open. If not OK, Refer to the Wiring Diagrams to identify possible causes of the circuit short. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test. Diagrams By Number
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E17 CHECK THE IWE SOLENOID OPERATION
- Connect: IWE Solenoid C1291.
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- Start the engine.
- With the IWE solenoid C1291 connected, connect a fused jumper wire between IWE solenoid C1291-2, circuit CCF05 (BN/BU), harness side and ground by carefully back-probing the IWE solenoid C1291.
- Measure the vacuum at the IWE solenoid output vacuum port.
- Is the IWE solenoid output port vacuum greater than 254 mm (10 in) Hg?
Yes
DISCONNECT the fused jumper. GO to E18.
No
INSTALL a new IWE solenoid. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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E18 CHECK THE IWE SOLENOID ACTIVATION CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between IWE solenoid C1291-2, circuit CCF05 (BN/BU), harness side and TCCM C2371A-6, circuit CCF05 (BN/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to E19.
No
REPAIR circuit CCF05 (BN/BU) for an open. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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E19 CHECK THE IWE SOLENOID ACTIVATION CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: IWE Solenoid C1291.
- Disconnect: TCCM C2371A.
- Ignition ON.
- Measure the voltage between IWE solenoid C1291-2, 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. REPEAT the self-test.
No
GO to E20.
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E20 CHECK THE IWE SOLENOID ACTIVATION CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: IWE Solenoid C1291.
- Disconnect: TCCM C2371A.
- Measure the resistance between IWE solenoid C1291-2, circuit CCF05 (BN/BU), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to E21.
No
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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E21 CHECK THE IWE 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.
- Measure the resistance between IWE solenoid C1291 pins 1 and 2, component side.
- Is the resistance between 44 and 70 ohms?
Yes
GO to E22.
No
INSTALL a new IWE solenoid. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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E22 CHECK THE TCCM
- Disconnect all TCCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all TCCM 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. REFER to Transfer Case Control Module (TCCM) Service and Repair. TEST the system for normal operation. REPEAT the self-test.
No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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E23 CHECK THE IWE VACUUM SYSTEM
- Ignition OFF.
- Disconnect both vacuum lines from the IWE solenoid.
- Using a vacuum pump, apply 508 mm (20 in) Hg of vacuum to the IWE system through the apply vacuum circuit.
- Observe the vacuum reading.
- Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute?
Yes
CONNECT the vacuum lines to the IWE solenoid. GO to E27.
No
GO to E24.
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E24 CHECK THE RH IWE LEAK RATE
- With the vehicle in NEUTRAL, position it on a hoist. Refer to Jacking and Lifting Service and Repair.
- Disconnect the vacuum line from the larger port on the RH IWE.
- Apply 508 mm (20 in) Hg of vacuum to the RH IWE port and observe vacuum reading.
- Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute?
Yes
GO to E25.
No
INSTALL a new RH IWE. REFER to Integrated Wheel End (IWE) Service and Repair. TEST the system for normal operation. REPEAT the self-test.
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E25 CHECK THE LH IWE LEAK RATE
- Disconnect the vacuum line from the larger port at the LH IWE.
- Apply 205 mm (20 in) Hg of vacuum to the LH IWE port and observe vacuum reading.
- Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute?
Yes
GO to E26.
No
INSTALL a new LH IWE. REFER to Integrated Wheel End (IWE) Service and Repair. TEST the system for normal operation. REPEAT the self-test.
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E26 CHECK THE IWE VACUUM SUPPLY TUBE
- Disconnect both vacuum lines from the IWE solenoid.
- Plug both LH and RH IWE vacuum lines. Apply 508 mm (20 in) Hg of vacuum to the IWE apply vacuum circuit and observe the vacuum reading.
- Does the vacuum maintain or drop less than 25 mm (1 in) Hg per minute?
Yes
GO to E27.
No
INSTALL new vacuum lines as necessary. TEST the system for normal operation. REPEAT the self-test.
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E27 CHECK THE IWE VACUUM SUPPLY AT EACH IWE IN 2H
- Connect a hand-held vacuum gauge to the LH IWE vacuum supply tube.
- NOTE: The engine must be idling during the following steps to supply the vacuum required for the IWEs to engage and disengage.
- Start the engine.
- Shift the transfer case to 2H while observing the vacuum gauge.
- Repeat these steps for the RH IWE.
- Are the vacuum readings greater than 254 mm (10 in) Hg?
Yes
GO to E30.
No
INSTALL new vacuum lines as necessary. TEST the system for normal operation. REPEAT the self-test.
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E28 CHECK THE LH IWE VACUUM LINE FOR AN OBSTRUCTION
- Ignition OFF.
- Disconnect both vacuum lines from the IWE solenoid.
- With the vehicle in NEUTRAL, position it on a hoist. Refer to Jacking and Lifting Service and Repair.
- Disconnect the vacuum line at the LH IWE.
- Connect a hand vacuum pump to the LH IWE vacuum line and attempt to draw a vacuum on the line.
- Did the vacuum pump draw a vacuum on the LH IWE vacuum line?
Yes
INSTALL a new vacuum line. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
No
CONNECT the vacuum line to the LH IWE. GO to E29.
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E29 CHECK THE RH IWE VACUUM LINE FOR AN OBSTRUCTION
- Disconnect the larger vacuum line at the RH IWE.
- Connect a vacuum pump to the RH IWE vacuum line and attempt to draw a vacuum on the line.
- Did the vacuum pump draw a vacuum on the RH IWE vacuum line?
Yes
INSTALL a new vacuum line. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
No
CONNECT the vacuum line to the RH IWE. GO to E30.
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E30 CHECK THE LH IWE OPERATION
- Ignition OFF.
- With the vehicle in NEUTRAL, position it on a hoist. Refer to Jacking and Lifting Service and Repair.
- Connect a vacuum pump with gauge to the larger port of the LH IWE.
- 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.
- Did the LH IWE disengage between 152 and 203 mm (6 to 8 in) Hg and engage when the vacuum is released?
Yes
GO to E31.
No
INSTALL a new LH IWE. REFER to Integrated Wheel End (IWE) Service and Repair. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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E31 CHECK THE RH IWE OPERATION
- Connect a vacuum pump with gauge to the larger port of the RH IWE.
- 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.
- Did the RH IWE disengage between 152 and 203 mm (6 to 8 in) Hg and engage when the vacuum is released?
Yes
CLEAR the DTCs. REPEAT the self-test. CARRY OUT the Mechanical Shift-On-The-Fly (MSOF) Functional Test. GO to Pinpoint Test J. Pinpoint Test J: Mechanical Shift-On-The-Fly (MSOF) Functional Test
No
INSTALL a new RH IWE. REFER to Integrated Wheel End (IWE) Service and Repair. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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