Jeep Cherokee (XJ): Diagnosis and testing. Service procedures. Removal and installation

Jeep Cherokee (XJ) 1984 - 2001 Service Manual > Brakes > Antilock brakes > Diagnosis and testing. Service procedures. Removal and installation

Diagnosis and testing

ANTILOCK BRAKES

The ABS brake system performs several self-tests every time the ignition switch is turned on and the vehicle is driven. The CAB monitors the systems input and output circuits to verify the system is operating correctly. If the on board diagnostic system senses that a circuit is malfunctioning the system will set a trouble code in its memory.

NOTE: An audible noise may be heard during the self-test. This noise should be considered normal.

NOTE: The MDS or DRB III scan tool is used to diagnose the ABS system. For additional information refer to the Antilock Brake section in Group 8W. For test procedures refer to the Chassis Diagnostic Manual.

Service procedures

BLEEDING ABS BRAKE SYSTEM

ABS system bleeding requires conventional bleeding methods plus use of the DRB scan tool. The procedure involves performing a base brake bleeding, followed by use of the scan tool to cycle and bleed the HCU pump and solenoids. A second base brake bleeding procedure is then required to remove any air remaining in the system.

(1) Perform base brake bleeding. Refer to base brake section for procedure.

(2) Connect scan tool to the Data Link Connector.

(3) Select ANTILOCK BRAKES, followed by MISCELLANEOUS, then ABS BRAKES. Follow the instructions displayed. When scan tool displays TEST COMPLETE, disconnect scan tool and proceed.

(4) Perform base brake bleeding a second time.

Refer to base brake section for procedure.

(5) Top off master cylinder fluid level and verify proper brake operation before moving vehicle.

Removal and installation

Hydraulic control unit/controller antilock brakes

REMOVAL

(1) Remove negative battery cable from the battery.

(2) Pull up on the CAB harness connector release (Fig. 4) and remove connector.

(3) Remove brake lines from the HCU.

(4) Remove HCU/CAB mounting nuts and bolt (Fig. 5) and remove HCU/CAB.

Fig. 4 CAB Harness Connector Release
Fig. 4 CAB Harness Connector Release

1 - CAB
2 - CAB HARNESS RELEASE

INSTALLATION

(1) Install HCU/CAB on the mounting studs.

(2) Install mounting nuts and bolt. Tighten to 11.5 N·m (102 in. lbs.).

(3) Install brake lines to the HCU and tighten to 19 N·m (170 in. lbs.).

(4) Install wiring harness connector to the CAB and push down on the release to secure the connector.

(5) Install negative battery cable to the battery.

(6) Bleed ABS brake system.

Fig. 5 HCU/CAB Mounting
Fig. 5 HCU/CAB Mounting

1 - HCU
2 - CAB
3 - HCU/CAB BRACKET
4 - MOTOR

Front wheel speed sensor

REMOVAL

(1) Raise vehicle and turn wheel outward for easier access to sensor.

(2) Remove sensor wire from mounting brackets.

(3) Clean sensor and surrounding area with shop towel before removal.

(4) Remove bolt attaching sensor to steering knuckle and remove sensor (Fig. 6).

(5) Remove sensor wire from brackets on body and steering knuckle.

(6) Unseat sensor wire grommet in wheel house panel.

(7) In engine compartment, disconnect sensor wire connector at harness plug. Then remove sensor and wire.

INSTALLATION

(1) If original sensor will be installed, wipe all traces of old spacer material off sensor pickup face.

Use a dry shop towel for this purpose.

(2) Apply Mopar Lock N' Seal or Loctite t 242 to bolt that secures sensor in steering knuckle. Use new sensor bolt if original bolt is worn or damaged.

(3) Position sensor on steering knuckle. Seat sensor locating tab in hole in knuckle and install sensor attaching bolt finger tight.

(4) Tighten sensor attaching bolt to 4.7 N·m (42 in.

lbs.).

(5) If original sensor has been installed, check sensor air gap. Air gap should be 0.36 to 1.5 mm (0.014 to 0.059 in.). If gap is incorrect, sensor is either loose, or damaged.

Fig. 6 Front Wheel Speed Sensor
Fig. 6 Front Wheel Speed Sensor

1 - WHEEL SPEED SENSOR PIGTAIL
2 - STEERING KNUCKLE
3 - TONE WHEEL
4 - FRONT WHEEL SPEED SENSOR

(6) Secure sensor wire to steering knuckle and body brackets.

(7) Route sensor wire forward and behind shock absorber. Then attach sensor wire to spring seat bracket with grommets on sensor wire.

(8) Route sensor wire to outer sill bracket. Remove all twists or kinks from wire.

(9) Attach sensor wire to sill bracket with grommet.

Be sure wire is free of twists and kinks.

(10) Verify sensor wire routing. Wire should loop forward and above sill bracket. Loose end of wire should be below sill bracket and towards brake hose.

(11) Seat sensor wire grommet in body panel and clip wire to brake line at grommet location.

(12) Connect sensor wire to harness in engine compartment.

Rear wheel speed sensor

REMOVAL

(1) Raise and fold rear seat forward for access to rear sensor connectors (Fig. 7).

(2) Disconnect sensors at rear harness connectors.

(3) Push sensor grommets and sensor wires through floorpan.

(4) Raise vehicle.

(5) Disconnect sensor wires at rear axle connectors.

(6) Remove wheel and tire assembly.

Fig. 7 Acceleration Switch And Rear Sensor Connections
Fig. 7 Acceleration Switch And Rear Sensor Connections

1 - REAR SEAT CROSSMEMBER
2 - ACCELERATION SENSOR
3 - SENSOR MOUNTING BRACKET
4 - TO R. R. WHEEL SENSOR
5 - TO L. R. WHEEL SENSOR
6 - FLOORPAN
7 - SENSOR HARNESS

(7) Remove brake drum.

(8) Remove clips securing sensor wires to brake lines, rear axle and, brake hose.

(9) Unseat sensor wire support plate grommet.

(10) Remove bolt attaching sensor to bracket and remove sensor (Fig. 8).

INSTALLATION

(1) If original sensor is being installed, remove any remaining pieces of cardboard spacer from sensor pickup face. Use dry shop towel only to remove old spacer material.

(2) Insert sensor wire through support plate hole.

Then seat sensor grommet in support plate.

(3) Apply Mopar Lock N' Seal or Loctite t 242 to original sensor bolt. Use new bolt if original is worn or damaged.

(4) Install sensor bolt finger tight only at this time.

(5) If original rear sensor was installed, adjust sensor air gap to 0.92-1.275 mm (0.036-0.05 in.). Use feeler gauge to measure air gap (Fig. 9). Tighten sensor bolt to 13 N·m (115 in. lbs.).

(6) If new sensor was installed, push cardboard spacer on sensor face against tone ring (Fig. 10).

Fig. 8 Rear Wheel Speed Sensor
Fig. 8 Rear Wheel Speed Sensor

1 - TONE WHEEL
2 - WHEEL SPEED SENSOR

Fig. 9 Setting Air Gap On Original Rear Sensor

Fig. 9 Setting Air Gap On Original Rear Sensor

1 - WHEEL SPEED SENSOR
2 - BRASS FEELER GAUGE
3 - TONE RING

Then tighten sensor bolt to 13 N·m (115 in. lbs.). Correct air gap will be established as tone ring rotates and peels spacer off sensor face.

(7) Route sensor wires to rear seat area.

(8) Feed sensor wires through floorpan access hole and seat sensor grommets in floorpan.

(9) Verify that rear sensor wires are secured to rear brake hose and axle with clips. Verify that wire is clear of rotating components.

(10) Install brake drum and wheel and tire assembly.

(11) Lower vehicle.

(12) Connect sensor wire to harness connector.

Then reposition carpet and fold rear seat down.

G-switch

REMOVAL

(1) Raise and fold rear seat assembly forward for access to sensor.

Fig. 10 New Rear Sensor
Fig. 10 New Rear Sensor

1 - REAR SENSOR
2 - AIR GAP SPACER ATTACHED TO SENSOR FACE

(2) Disconnect switch harness.

(3) Remove switch mounting screws (Fig. 11) (4) Remove the acceleration switch.

Fig. 11 G-Switch Mounting
Fig. 11 G-Switch Mounting

1 - ACCELERATION SWITCH
2 - SWITCH BRACKET
3 - REAR SEAT CROSSMEMBER

INSTALLATION

CAUTION: The mercury switch (inside the G-switch), will not function properly if the switch is installed incorrectly. Verify that the switch locating arrow is pointing to the front of the vehicle (Fig.

12).

(1) Position switch in mounting bracket.

(2) Install switch mounting bolts and tighten to 3 N·m (27.5 in. lbs.).

Fig. 12 G-Switch
Fig. 12 G-Switch

1 - SWITCH PART NUMBER
2 - ARROW INDICATES FRONT OF SWITCH FOR PROPER MOUNTING

(3) Connect harness to switch. Be sure harness connector is firmly seated.

(4) Move seat back to normal position.

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