Pinpoint Test U: The Front Axle Does Not Engage/Disengage Correctly
Four Wheel Drive (4WD) Systems - Electronic Shift
Pinpoint Tests
Pinpoint Test U: 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: Short Circuit To Ground) - Fault sets when TCCM C2371A pin 6 detects a short to ground. IWEs are engaged regardless of mode selected when DTC is present.
- DTC C1979:12 ( IWE Solenoid Circuit Failure: Short Circuit To Battery) - Fault sets when TCCM C2371A pin 6 detects a short to voltage. IWEs are disengaged regardless of mode selected when DTC is present.
- DTC C1979:13 ( IWE Solenoid Circuit Failure: Circuit Open) - Fault sets when TCCM C2371A pin 6 detects an open circuit. IWEs are engaged regardless of mode selected when DTC is present.
This pinpoint test is intended to diagnose the following:
- Mode Select Switch (MSS)
- IWEs
- IWE solenoid
- Transfer case
- Vacuum leaks
- Front axle assembly
- TCCM
- Wiring, terminals or connectors
- Fuses
PINPOINT TEST U: 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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U1 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 U20.
For DTC C1979:12, GO to U19.
For DTC C1979:13, GO to U16.
For all other DTCs, REFER to the Transfer Case Control Module (TCCM) DTC Chart. Four Wheel Drive (4WD) Systems - Electronic Shift
No
GO to U2.
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U2 CHECK FOR GRINDING NOISES AT HIGH SPEEDS
- Turn the MSS from 2H to 4H at rest. Drive the vehicle.
- Turn the MSS from 2H to 4H while driving the vehicle below 5 km/h (3 mph).
- Turn the MSS from 2H to 4H while driving the vehicle above 32 km/h (20 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.
No
GO to U3.
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U3 CHECK THE TRANSFER CASE SHIFT TO 2H
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- Command the Transfer Case Shift Motor Position Sense Contact Plate Power Circuit Status (PLATE_PWR_OS) PID to energize the transfer case shift motor contact plate position return circuit.
- Monitor the Transfer Case Contact Plate Switch A (PLATE_A), B (PLATE_B), C (PLATE_C) and D (PLATE_D) PIDs with the MSS in 2H.
- Did the PIDs and message center indicate the vehicle shifted into 2H (4X2 displayed in message center for approximately 4 seconds)?
Yes
GO to U4.
No
GO to Pinpoint Test S. Pinpoint Test S: The Vehicle Does Not Shift Between 2H and 4H Correctly and/or Grinding Noise Heard During Four-Wheel Drive (4W
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U4 CHECK THE IWE DISENGAGEMENT
- With the vehicle in NEUTRAL, position it on a hoist. 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 and allow to idle.
- 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 U10.
No
GO to U5.
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U5 CHECK THE TRANSFER CASE SHIFT INTO 4H
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- Command the Transfer Case Shift Motor Position Sense Contact Plate Power Circuit Status (PLATE_PWR_OS) PID to energize the transfer case shift motor contact plate position return circuit.
- Monitor the Transfer Case Contact Plate Switch A (PLATE_A), B (PLATE_B), C (PLATE_C) and D (PLATE_D) PIDs with the MSS in 4H.
- Did the PIDs and message center indicate that the vehicle shifted into 4H (4X4 HIGH)?
Yes
GO to U6.
No
GO to Pinpoint Test S. Pinpoint Test S: The Vehicle Does Not Shift Between 2H and 4H Correctly and/or Grinding Noise Heard During Four-Wheel Drive (4W
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U6 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 U7.
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U7 CHECK THE IWE SOLENOID OUTPUT IN 4H
- Disconnect the output vacuum line at the IWE solenoid.
- Switch the MSS to 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, measure the vacuum at the output port of the IWE solenoid.
- Is the vacuum less than 25 mm (1 in) Hg?
Yes
Ignition in the OFF position. GO to U28.
No
GO to U8.
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U8 CHECK THE IWE SOLENOID OUTPUT IN 4H USING THE IWEs OUTPUT CONTROL (IWE_OS) PID
- 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, command the IWE_OS PID 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 U22.
No
GO to U9.
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U9 CHECK THE IWE SOLENOID
- Disconnect: 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.
- With the engine still running, measure the vacuum at the output port of the IWE solenoid.
- Is the vacuum less than 25 mm (1 in) Hg?
Yes
GO to U20.
No
INSTALL a new IWE solenoid. TEST the system for normal operation.
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U10 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.
- Start the engine.
- Disconnect the output vacuum line at the IWE solenoid while having the vacuum supply attached to the solenoid.
- With the engine running and the MSS in 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 U23.
No
GO to U11.
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U11 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 U15.
No
GO to U12.
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U12 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 U13.
No
REPAIR or INSTALL a new source vacuum line. TEST the system for normal operation.
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U13 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 U14.
No
INSTALL a new vacuum reservoir. TEST the system for normal operation.
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U14 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 Electronic Shift-On-The-Fly (ESOF) Functional Test. GO to Pinpoint Test Z. Pinpoint Test Z: Electronic Shift-On-The-Fly (ESOF) Functional Test
No
REPAIR or INSTALL new vacuum lines or INSTALL a check valve. TEST the system for normal operation.
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U15 CHECK THE IWE SOLENOID OUTPUT IN 2H MODE USING THE IWEs OUTPUT CONTROL (IWE_OS) PID
- Enter the following diagnostic mode on the scan tool: DataLogger - TCCM.
- Connect all disconnected vacuum lines.
- 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, command IWE_OS PID 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
END the active command. GO to U22.
No
GO to U16.
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U16 CHECK FOR VOLTAGE TO THE 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
END the active command. GO to U17.
No
CHECK Battery Junction Box (BJB) fuse 29 (10A). If OK, REPAIR circuit SBB29 (GY/RD). 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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U17 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 IWE solenoid C1291 connected, connect a fused jumper wire between IWE solenoid C1291-2, circuit CCF05 (BN/BU), component 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 U18.
No
INSTALL a new IWE solenoid. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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U18 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 U19.
No
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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U19 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 U20.
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U20 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 U21.
No
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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U21 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 U22.
No
INSTALL a new IWE solenoid. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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U22 CHECK FOR CORRECT TCCM OPERATION
- Ignition OFF.
- 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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U23 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 U27.
No
GO to U24.
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U24 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 U25.
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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U25 CHECK THE LH IWE LEAK RATE
- Disconnect the vacuum line from the larger port at the LH IWE.
- Apply 508 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 U26.
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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U26 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 U27.
No
INSTALL new vacuum lines as necessary. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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U27 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.
- Switch the MSS 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 U30.
No
INSTALL new vacuum lines as necessary. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
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U28 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 U29.
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U29 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 U30.
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U30 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 U31.
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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U31 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 Electronic Shift-On-The-Fly (ESOF) Functional Test. GO to Pinpoint Test Z. Pinpoint Test Z: Electronic Shift-On-The-Fly (ESOF) 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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