Pinpoint Test K: The Front Axles Do Not Engage/Disengage Correctly
Four Wheel Drive (4WD) Systems - Electronic Shift
Pinpoint Test K: The Front Axles Do Not Engage/Disengage Correctly
Normal Operation
In 4H or 4L mode the Transfer Case Control Module (TCCM) supplies a ground path to the hublock vacuum solenoid to apply vacuum to the Constant Vacuum Hublocks (CVHs), engaging the front hubs to the front axle shafts. A minimum vacuum level of 6 inches of Hg is required to correctly operate the CVH (Constant Vacuum Hublock) system. In 2H mode the TCCM (Transfer Case Control Module) does not supply the ground path to the hublock vacuum solenoid, vacuum is not applied to the CVHs (Constant Vacuum Hublocks) and an internal spring in each CVH (Constant Vacuum Hublock) keeps the hubs disengaged.
- DTC C1010:00 (Constant Vacuum Hublock (CVH) Solenoid: No Sub Type Information)- Fault sets when the Transfer Case Control Module (TCCM) determines a CVH (Constant Vacuum Hublock) system fault is present based on wheel speed and steering wheel angle message data. When the DTC is present on-demand the CVHs (Constant Vacuum Hublocks) are disengaged from the front axle shafts regardless of the mode selected.
- DTC C1010:11 (Constant Vacuum Hublock (CVH) Solenoid: Circuit short to Ground)- Fault sets when the TCCM (Transfer Case Control Module) C2371A pin 6 detects a short to ground. When the DTC is present on-demand the CVHs (Constant Vacuum Hublocks) are engaged to the front axle shafts regardless of the mode selected.
- DTC C1010:12 (Constant Vacuum Hublock (CVH) Solenoid: Circuit Short to Battery)- Fault sets when the Transfer Case Control Module (TCCM) C2371A pin 6 detects a short to voltage. When the DTC is present on-demand the CVHs (Constant Vacuum Hublocks) are disengaged from the front axle shafts regardless of the mode selected.
- DTC C1010:13 (Constant Vacuum Hublock (CVH) Solenoid: Circuit Open)- Fault sets when the Transfer Case Control Module (TCCM) C2371A pin 6 detects an open circuit. When the DTC is present on-demand the CVHs (Constant Vacuum Hublocks) are disengaged from the front axle shafts regardless of the mode selected.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Vacuum leaks
- Hublock vacuum solenoid
- CVH (Constant Vacuum Hublock)
- Transfer case
- Front axle assembly
- TCCM (Transfer Case Control Module)
PINPOINT TEST K : THE FRONT AXLES DO 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.
NOTE: 4H (4X4 HIGH) and 4L (4X4 LOW) are not intended for driving on hard/dry surfaces.
NOTE: Make sure both CVH (Constant Vacuum Hublock) dials are in AUTO mode position.
K1 CHECK FOR 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 C1010:00, GO to K23.
For DTC C1010:11, GO to K20.
For DTC C1010:12, GO to K18.
For DTC C1010:13, GO to K19.
For all other DTCs, REFER to the Transfer Case Control Module (TCCM) DTC Chart. Four Wheel Drive (4WD) Systems - Electronic Shift
No
GO to K2.
K2 CHECK FOR GRINDING NOISES AT HIGH SPEEDS
- Make sure both CVH (Constant Vacuum Hublock) dials are in AUTO mode position.
- Turn the MSS (Mode Select Switch) from 2H to 4H at rest. Drive the vehicle. Turn the MSS (Mode Select Switch) back to 2H.
- Turn the MSS (Mode Select Switch) from 2H to 4H while driving the vehicle below 5 km/h (3 mph). Turn the MSS (Mode Select Switch) back to 2H.
- Turn the MSS (Mode Select Switch) from 2H to 4H while driving the vehicle above 32 km/h (20 mph). Turn the MSS (Mode Select Switch) back to 2H.
Is the axle system fully functional at rest, but there is a grinding noise during engagement, especially at high speed?
Yes
REFER to Differential Assembly &/or Axle Shaft Assembly &/or Drive/Propeller Shafts, Bearings and Joints to diagnose excessive front axle noise/chatter/grinding during 4X4 engagement.
No
GO to K3.
K3 CHECK THE TRANSFER CASE SHIFT TO 2H
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).
- Command the Transfer Case Contact Plate Power (PLATE_PWR_OS) PID to energize the transfer case gearmotor encoder assembly.
- Monitor the Transfer Case Contact Plate Switch A (PLATE_A), B (PLATE_B), C (PLATE_C) and D (PLATE_D) PIDs with the MSS (Mode Select Switch) in 2H.
MSS (Mode Select Switch) Position Contact Plate Position PLATE_A PLATE_B PLATE_C PLATE_D 2H Mode CLOSED CLOSED OPEN CLOSED
Did the PIDs indicate the vehicle shifted into 2H?
Yes
GO to K4.
No
GO to Pinpoint Test I. Pinpoint Test I: The Vehicle Does Not Shift Between 2H and 4H Modes Correctly
K4 CHECK THE CVH (Constant Vacuum Hublock) DISENGAGEMENT
NOTE: The engine must be idling during the following steps to supply the vacuum required for the CVH (Constant Vacuum Hublock) to engage and disengage.
- With the vehicle in NEUTRAL, position it on a hoist.
- Start the engine and allow to idle.
- Make sure both CVH (Constant Vacuum Hublock) dials are in AUTO mode position.
- Rotate the LH front tire one revolution forward and one revolution backward while observing the LH front axle shaft.
- Rotate the RH front tire one revolution forward and one revolution backward while observing the RH front axle shaft.
Did either front axle shaft rotate?
Yes
GO to K10.
No
GO to K5.
K5 CHECK THE TRANSFER CASE SHIFT INTO 4H
- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).
- Command the Transfer Case Contact Plate Power (PLATE_PWR_OS) PID to energize the transfer case gearmotor encoder assembly.
- Monitor the Transfer Case Contact Plate Switch A (PLATE_A), B (PLATE_B), C (PLATE_C) and D (PLATE_D) PIDs with the MSS (Mode Select Switch) in 4H.
MSS (Mode Select Switch) Position Contact Plate Position PLATE_A PLATE_B PLATE_C PLATE_D 4H Mode OPEN CLOSED OPEN CLOSED
Did the PIDs and message center indicate that the vehicle shifted into 4H (4X4 HIGH)?
Yes
GO to K6.
No
GO to Pinpoint Test I. Pinpoint Test I: The Vehicle Does Not Shift Between 2H and 4H Modes Correctly
K6 CHECK THE CVH (Constant Vacuum Hublock) ENGAGEMENT IN 4H
- Make sure both CVH (Constant Vacuum Hublock) dials are in AUTO mode position.
- With the engine still running, rotate the LH front tire one revolution forward and one revolution backward while observing the LH front axle shaft.
- Rotate the RH front tire one revolution forward and one revolution backward while observing the RH front axle shaft.
Did both front axle shafts rotate?
Yes
CVH (Constant Vacuum Hublock) and Transfer Case operation is normal. CHECK that all driveline fasteners are present and tightened to specification. For further diagnosis of the front axle, REFER to Differential Assembly &/or Axle Shaft Assembly &/or Drive/Propeller Shafts, Bearings and Joints.
No
GO to K7.
K7 CHECK THE HUBLOCK VACUUM SOLENOID OUTPUT IN 4H
- Disconnect the output vacuum line at the hublock vacuum solenoid.
- Switch the MSS (Mode Select Switch) to 4H.
- With the engine still running, measure the vacuum at the output port of the hublock vacuum solenoid.
Is the vacuum greater than 152 mm (6 in) Hg?
Yes
GO to K23.
No
GO to K8.
K8 CHECK THE HUBLOCK VACUUM SOLENOID OUTPUT IN 4H USING THE CVH (Constant Vacuum Hublock) OUTPUT CONTROL (CV_HUB_OS) PID
- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).
- With the engine still running, command the CV_HUB_OS PID to engage the CVH (Constant Vacuum Hublock) (PID status On).
- Measure the vacuum at the output port of the hublock vacuum solenoid.
Is the vacuum greater than 152 mm (6 in) Hg?
Yes
END the active command. GO to K22.
No
GO to K9.
K9 CHECK THE HUBLOCK VACUUM SOLENOID
- Disconnect: CVH (Constant Vacuum Hublock) Solenoid C1291.
- With the engine still running, measure the vacuum at the output port of the hublock vacuum solenoid.
Is the vacuum greater than 152 mm (6 in) Hg?
Yes
GO to K20.
No
INSTALL a new hublock vacuum solenoid. Hublock Vacuum Solenoid . TEST the system for normal operation.
K10 CHECK THE HUBLOCK VACUUM SOLENOID OUTPUT VACUUM IN 2H
- Start the engine.
- Disconnect the output vacuum line at the hublock vacuum solenoid while having the vacuum supply attached to the hublock vacuum solenoid.
- With the engine running and the MSS (Mode Select Switch) in the 2H position, measure the vacuum at the output port of the hublock vacuum solenoid.
Is the vacuum less than 25 mm (1 in) Hg?
Yes
GO to K23.
No
GO to K11.
K11 CHECK THE HUBLOCK VACUUM SOLENOID INPUT VACUUM
- Disconnect the supply vacuum line at the hublock vacuum solenoid.
- With the engine still running, measure the supply line vacuum to the hublock vacuum solenoid.
Is the vacuum greater than 152 mm (6 in) Hg?
Yes
GO to K15.
No
GO to K12.
K12 CHECK SOURCE VACUUM TO THE VACUUM RESERVOIR
- Disconnect the source vacuum line from the vacuum reservoir.
- With the engine still running, measure the source vacuum being supplied to the vacuum reservoir.
Is the vacuum greater than 152 mm (6 in) Hg?
Yes
GO to K13.
No
REPAIR or INSTALL a new source vacuum line. TEST the system for normal operation.
K13 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
Vehicles equipped with gasoline engines, GO to K14. Vehicles equipped with diesel engines, GO to K15.
No
INSTALL a new vacuum reservoir. TEST the system for normal operation.
K14 CHECK THE VACUUM CHECK VALVE
- NOTE: A check valve is between the vacuum source and the reservoir (gasoline engines only).
Connect the vacuum lines to the hublock vacuum solenoid.
- Connect a vacuum pump to the hublock vacuum 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 O. Pinpoint Test O: 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.
K15 CHECK THE HUBLOCK VACUUM SOLENOID OUTPUT IN 2H MODE USING THE CVH (Constant Vacuum Hublock) OUTPUT CONTROL (CV_HUB_OS) PID
NOTE: The engine must be idling during the following steps to supply the vacuum required for the CVH (Constant Vacuum Hublock) to disengage.
- Enter the following diagnostic mode on the scan tool: DataLogger- TCCM (Transfer Case Control Module).
- With the engine still running, command CV_HUB_OS PID to disengage the CVH (Constant Vacuum Hublock) (PID status No).
- Measure the vacuum at the output port of the hublock vacuum solenoid.
Is the vacuum less than 25 mm (1 in) Hg?
Yes
END the active command. GO to K22.
No
GO to K16.
K16 CHECK FOR VOLTAGE TO THE HUBLOCK VACUUM SOLENOID
- Disconnect: CVH (Constant Vacuum Hublock) Solenoid C1291.
- Measure the voltage between CVH (Constant Vacuum Hublock) solenoid C1291-1, circuit SBB39 (WH/RD), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to K17.
No
CHECK Battery Junction Box (BJB) fuse 39 (10A). If OK, REPAIR circuit SBB39 (WH/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. [1][2]Diagrams By Number
K17 CHECK THE HUBLOCK VACUUM SOLENOID OPERATION
NOTE: The engine must be idling during the following steps to supply the vacuum required for the CVH (Constant Vacuum Hublock) to engage.
- Connect: CVH (Constant Vacuum Hublock) Solenoid C1291.
- Start the engine.
- With CVH (Constant Vacuum Hublock) solenoid C1291 connected, connect a fused jumper wire between CVH (Constant Vacuum Hublock) solenoid C1291-2, circuit CCF05 (BN/BU), component side and ground by carefully back-probing the CVH (Constant Vacuum Hublock) solenoid C1291.
- Measure the vacuum at the CVH (Constant Vacuum Hublock) solenoid output vacuum port.
Is the hublock vacuum solenoid output port vacuum greater than 152 mm (6 in) Hg?
Yes
DISCONNECT the fused jumper. GO to K18.
No
INSTALL a new hublock vacuum solenoid. REFER to Hublock Vacuum Solenoid . CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
K18 CHECK THE HUBLOCK VACUUM SOLENOID ACTIVATION CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: CVH (Constant Vacuum Hublock) Solenoid C1291.
- Disconnect: TCCM (Transfer Case Control Module) C2371A.
- Ignition ON.
- Measure the voltage between CVH (Constant Vacuum Hublock) 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 K19.
K19 CHECK THE HUBLOCK VACUUM SOLENOID ACTIVATION CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: CVH (Constant Vacuum Hublock) Solenoid C1291.
- Disconnect: TCCM (Transfer Case Control Module) C2371A.
- Measure the resistance between CVH (Constant Vacuum Hublock) solenoid C1291-2, 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 5 ohms?
Yes
GO to K20.
No
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
K20 CHECK THE HUBLOCK VACUUM SOLENOID ACTIVATION CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: CVH (Constant Vacuum Hublock) Solenoid C1291.
- Disconnect: TCCM (Transfer Case Control Module) C2371A.
- Measure the resistance between CVH (Constant Vacuum Hublock) solenoid C1291-2, circuit CCF05 (BN/BU), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to K21.
No
REPAIR circuit CCF05 (BN/BU). CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
K21 CHECK THE HUBLOCK VACUUM 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 CVH (Constant Vacuum Hublock) solenoid C1291 pins 1 and 2, component side.
Is the resistance between 44 and 70 ohms?
Yes
GO to K22.
No
INSTALL a new hublock vacuum solenoid. REFER to Hublock Vacuum Solenoid . CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
K22 CHECK FOR CORRECT TCCM (Transfer Case Control Module) OPERATION
- Ignition OFF.
- Disconnect all TCCM (Transfer Case Control Module) connectors.
- Check for:
- corrosion.
- 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 Transfer Case Control Module (TCCM) . 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.
K23 CHECK THE CVH (Constant Vacuum Hublock) VACUUM HOSES
- Ignition OFF.
- Disconnect the vacuum harness from the CVH (Constant Vacuum Hublock) solenoid.
- Disconnect and plug the LH and RH CVH (Constant Vacuum Hublock) vacuum tubes at the knuckles.
- Connect a vacuum pump to the output hose going to the LH and RH knuckles at the CVH (Constant Vacuum Hublock) solenoid connection. Apply 508 mm (20 in) Hg of vacuum to the CVH (Constant Vacuum Hublock) apply vacuum circuit and observe the vacuum reading.
Did the vacuum drop more than 25 mm (1 in) Hg per minute?
Yes
INSTALL new vacuum tubes as necessary. TEST the system for normal operation.
No
GO to K24.
K24 CHECK THE LH CVH (Constant Vacuum Hublock) VACUUM LINE FOR AN OBSTRUCTION
- With the vehicle in NEUTRAL, position it on a hoist.
- Remove the plug from the vacuum line at the LH knuckle.
- Connect a hand vacuum pump to the LH CVH (Constant Vacuum Hublock) vacuum line and attempt to draw a vacuum on the line.
Did the vacuum pump draw a vacuum on the LH CVH (Constant Vacuum Hublock) vacuum line?
Yes
INSTALL a new vacuum line. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
No
GO to K25.
K25 CHECK THE RH CVH (Constant Vacuum Hublock) VACUUM LINE FOR AN OBSTRUCTION
- Remove the plug from the vacuum line at the RH knuckle.
- Connect a vacuum pump to the RH CVH (Constant Vacuum Hublock) vacuum line and attempt to draw a vacuum on the line.
Did the vacuum pump draw a vacuum on the RH CVH (Constant Vacuum Hublock) vacuum line?
Yes
INSTALL a new vacuum line. CLEAR the DTCs. TEST the system for normal operation. REPEAT the self-test.
No
GO to K26.
K26 CHECK FOR LEAKS AT THE LH AND RH CVH (Constant Vacuum Hublock)
- Connect a vacuum pump to the knuckle fitting.
- Apply 508 mm (20 in) Hg of vacuum. Observe the vacuum reading for 1 minute.
Is the vacuum drop less than 25 mm (1 in) Hg per minute?
Yes
GO to K28.
No
GO to K27.
K27 CHECK FOR A LOOSE KNUCKLE FITTING
- Remove the vacuum pump from the knuckle.
- Make sure the knuckle fitting is tightened to 20 Nm (177 lb-in).
- Install the vacuum pump on the knuckle and pump to 508 mm (20 in) Hg.
- Observe the vacuum reading for 1 minute.
Is the vacuum drop less than 25 mm (1 in) Hg per minute?
Yes
The knuckle fitting was the source of the leak. TEST the system for normal operation.
No
GO to K28.
K28 CHECK FOR A DYNAMIC VACUUM LEAK AT THE LH AND RH CVH (Constant Vacuum Hublock)
- Make sure the vacuum is still at 508 mm (20 in) Hg.
- Rotate the front tire for 1 minute while observing the vacuum reading.
Is the vacuum drop greater than 25 mm (1 in) Hg per minute?
Yes
GO to K29.
No
The 4WD (Four-Wheel Drive) system is operating correctly. TEST the system for normal operation.
K29 CHECK FOR A HUBLOCK VACUUM LEAK
- Remove the hublock. Refer to Hublock .
- Remove and discard the hublock O-ring.
- Rotate the hublock to AUTO position.
- Install the hublock into the Hublock Vacuum Test Stand. Be sure that the hublock is completely seated into the Hublock Vacuum Test Stand.
- Connect the vacuum pump and pump to 508 mm (20 in) Hg. Observe the vacuum reading for 1 minute.
Is the vacuum drop less than 25 mm (1 in) Hg per minute?
Yes
The hublock is OK. GO to K30.
No
INSTALL a new hublock. REFER to Hublock . TEST the system for normal operation.
K30 CHECK THE HUBLOCK SEAL
NOTE: Install a new O-ring on the Vacuum Hub Test Tool. The O-ring used is the same as in the hublock. Apply a light film of lubricant on the O-ring.
NOTE: Using emery cloth, clean the sealing surface of the wheel hub before testing.
- Install the Vacuum Hub Test Tool and the retainer ring. Make sure the retainer ring is seated in the groove.
- Connect the vacuum pump and pump to 508 mm (20 in) Hg. Observe the vacuum reading for 1 minute.
Is the vacuum drop less than 25 mm (1 in) Hg per minute?
Yes
The old hublock seal was worn or damaged. REMOVE the Vacuum Hub Test Tool. INSTALL the hublock with a new O-ring. TEST the system for normal operation.
No
GO to K31.
K31 CHECK THE KNUCKLE SEAL
- Remove the wheel hub assembly.
- NOTE: Install a new O-ring on the Knuckle Seal Vacuum Test Tool. The O-ring used is the same as in the hublock. Apply a light film of lubricant on the O-ring.
NOTE: Using emery cloth, clean the sealing surface of the wheel hub before testing.
Install the Knuckle Seal Vacuum Test Tool.
- Connect the vacuum pump to the knuckle fitting and apply 508 mm (20 in) Hg of vacuum. If checking for a dynamic leak, carefully rotate the U-joint while observing the vacuum reading for 1 minute.
Is the vacuum drop less than 25 mm (1 in) Hg per minute?
Yes
GO to K32.
No
INSTALL a new knuckle seal. RESTORE the system to normal condition. TEST the system for normal operation.
K32 CHECK THE WHEEL HUB O-RING
- Remove and discard the wheel hub O-ring.
- NOTE: Apply a light film of lubricant on the Vacuum Hub Test Tool O-ring.
NOTE: Do not remove the ABS sensor.
Install the Vacuum Hub Test Tool and the retainer ring. Make sure the retainer ring is seated in the groove.
- Install a new O-ring on the wheel hub.
- Install the Hub Bearing Vacuum Test Stand. Make sure the tool is seated over the wheel hub seal.
- Connect the vacuum pump and pump to 508 mm (20 in) Hg. If checking for a dynamic leak, carefully rotate the hub flange relative to the wheel bearing flange while observing the vacuum reading for 1 minute.
Is the vacuum drop less than 25 mm (1 in) Hg per minute?
Yes
The old wheel hub O-ring was worn or damaged. REMOVE the Hub Bearing Vacuum Test Stand. RESTORE the system to normal condition. TEST the system for normal operation.
No
GO to K33.
K33 CHECK THE WHEEL HUB ASSEMBLY
- Remove the wheel speed sensor.
- Install the Hub Bearing Vacuum Test Stand and the ABS Sensor Vacuum Test Plug.
- Connect the vacuum pump and pump to 508 mm (20 in) Hg. Observe the vacuum reading for 1 minute.
Is the vacuum drop less than 25 mm (1 in) Hg per minute?
Yes
REMOVE the Hub Bearing Vacuum Test Stand and the ABS Sensor Vacuum Test Plug. INSTALL a new wheel speed sensor. TEST the system for normal operation.
No
REMOVE the Hub Bearing Vacuum Test Stand and the ABS Sensor Vacuum Test Plug. INSTALL a new wheel hub assembly. TEST the system for normal operation.