Jeep XJ. Manual — part 55
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 oper-
ating 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 informa-
tion refer to the Antilock Brake section in Group
8W. For test procedures refer to the Chassis Diag-
nostic Manual.
SERVICE PROCEDURES
BLEEDING ABS BRAKE SYSTEM
ABS system bleeding requires conventional bleed-
ing methods plus use of the DRB scan tool. The pro-
cedure 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 bleed-
ing 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 MIS-
CELLANEOUS, 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 bat-
tery.
(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.
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 connec-
tor.
(5) Install negative battery cable to the battery.
(6) Bleed ABS brake system.
Fig. 3 G-Switch
1 – SWITCH PART NUMBER
2 – ARROW INDICATES FRONT OF SWITCH FOR PROPER
MOUNTING
Fig. 4 CAB Harness Connector Release
1 – CAB
2 – CAB HARNESS RELEASE
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BRAKES
XJ
DESCRIPTION AND OPERATION (Continued)
FRONT WHEEL SPEED SENSOR
REMOVAL
(1) Raise vehicle and turn wheel outward for eas-
ier 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 sen-
sor 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 sen-
sor 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.
(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 grom-
met. 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 com-
partment.
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 connec-
tors.
(6) Remove wheel and tire assembly.
Fig. 5 HCU/CAB Mounting
1 – HCU
2 – CAB
3 – HCU/CAB BRACKET
4 – MOTOR
Fig. 6 Front Wheel Speed Sensor
1 – WHEEL SPEED SENSOR PIGTAIL
2 – STEERING KNUCKLE
3 – TONE WHEEL
4 – FRONT WHEEL SPEED SENSOR
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BRAKES
5 - 37
REMOVAL AND INSTALLATION (Continued)
(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 sen-
sor 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 sen-
sor 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).
Then tighten sensor bolt to 13 N·m (115 in. lbs.). Cor-
rect 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 assem-
bly.
(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. 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
Fig. 8 Rear Wheel Speed Sensor
1 – TONE WHEEL
2 – WHEEL SPEED SENSOR
Fig. 9 Setting Air Gap On Original Rear Sensor
1 – WHEEL SPEED SENSOR
2 – BRASS FEELER GAUGE
3 – TONE RING
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BRAKES
XJ
REMOVAL AND INSTALLATION (Continued)
(2) Disconnect switch harness.
(3) Remove switch mounting screws (Fig. 11)
(4) Remove the acceleration switch.
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.).
(3) Connect harness to switch. Be sure harness
connector is firmly seated.
(4) Move seat back to normal position.
DISASSEMBLY AND ASSEMBLY
HYDRAULIC CONTROL UNIT/CONTROLLER
ANTILOCK BRAKE
DISASSEMBLY
(1) Remove pump motor connector from the CAB.
(2) Remove CAB mounting screws from the HCU
(Fig. 13).
(3) Remove CAB from the HCU.
Fig. 10 New Rear Sensor
1 – REAR SENSOR
2 – AIR GAP SPACER ATTACHED TO SENSOR FACE
Fig. 11 G-Switch Mounting
1 – ACCELERATION SWITCH
2 – SWITCH BRACKET
3 – REAR SEAT CROSSMEMBER
Fig. 12 G-Switch
1 – SWITCH PART NUMBER
2 – ARROW INDICATES FRONT OF SWITCH FOR PROPER
MOUNTING
Fig. 13 CAB Mounting Screws
1 – MOUNTING SCREWS
2 – CAB
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BRAKES
5 - 39
REMOVAL AND INSTALLATION (Continued)
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