Jeep XJ. Manual — part 573
Symptom:
LEFT FRONT SENSOR SIGNAL FAILURE
When Monitored and Set Condition:
LEFT FRONT SENSOR SIGNAL FAILURE
When Monitored:
Wheel speed comparison is checked at drive off or every 7 milliseconds
(ms). Sensor circuit continuity is checked every 7 milliseconds. Wheel speed phase length
supervision is checked every 7 milliseconds.
Set Condition:
If, during an ABS stop, the CAB commands any valve solenoid on for an
extended length of time, and does not see a corresponding wheel speed change, the
Diagnostic Trouble Code (DTC) is set. The DTC can also set if the signal is missing or
erratic.
POSSIBLE CAUSES
BOTH LEFT FRONT WHEEL SPEED SENSOR CIRCUIT AND SIGNAL DTC CONDITIONS
PRESENT
LEFT FRONT WHEEL SPEED SENSOR OR CONNECTOR DAMAGED
TONE WHEEL DAMAGED
LEFT FRONT WHEEL SPEED SENSOR AIR GAP OUT OF SPECIFICATION
LEFT FRONT WHEEL BEARING OUT OF SPECIFICATION
LEFT FRONT WHEEL SPEED SENSOR INOPERATIVE
CAB - WON’T RESPOND TO LEFT FRONT WHEEL SPEED SENSOR SIGNAL
INTERMITTENT SIGNAL DTC
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, read DTC’s.
Are both Left Front Sensor Signal Failure and Left Front Sensor Circuit Failure
displayed?
All
Yes
→
Refer to symptom Left Front Sensor Circuit Failure in the
BRAKES Category.
Perform ABS VERIFICATION TEST - VER 1.
No
→
2
Turn the ignition on.
Using the DRBIII
t, monitor the Left Front Wheel Speed Sensor while an assistant
drives the vehicle.
Slowly accelerate as straight as possible from a stop to 24 Km/h (15 Mph).
With the DRBIII
t, monitor all wheel speed sensors.
Is Left Front WSS Signal 0 Km/h (0 Mph) or differing from others by more than 5kmh
(3mph)?
All
Yes
→
No
→
23
BRAKES (CAB)
TEST
ACTION
APPLICABILITY
3
Turn the ignition off.
Inspect the Left Front Wheel Speed Sensor and Connector.
Is the Sensor or Connector Damaged?
All
Yes
→
Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No
→
4
Turn the ignition off.
Inspect the Tone Wheel for damaged or missing teeth, cracks, or looseness.
Note: The Tone Wheel Teeth should be perfectly square, not bent or nicked.
Is the Tone Wheel OK?
All
Yes
→
No
→
Replace the Tone Wheel.
Perform ABS VERIFICATION TEST - VER 1.
5
Turn the ignition off.
Using a Feeler Gauge, measure the Wheel Speed Sensor Air Gap.
NOTE: The Air Gap should be checked in at least four places on the Tone
Wheel.
Is the Air Gap between 0.42 mm - 1.71 mm (0.017
9 - 0.0689) ?
All
Yes
→
No
→
Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
6
Turn the ignition off.
Inspect the wheel bearings for excessive runout or clearance.
Note: Refer to the appropriate service information, if necessary, for proce-
dures or specifications.
Is the bearing clearance OK ?
All
Yes
→
No
→
Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
7
Turn the ignition off.
Disconnect the CAB connector.
Raise the left front wheel off the ground.
Using a voltmeter in Alternating Current (AC) mode, measure the Left Front Wheel
Speed Sensor (+) Signal Circuit and Left Front Wheel Speed Sensor (-) Circuit at the
CAB connector.
Quickly rotate the wheel by spinning the tire by hand.
Measure the Alternating Current (AC) voltage of the Left Front Wheel Speed Sensor
Circuit.
Does the voltage go above 650 millivolts as the wheel is rotated?
All
Yes
→
Replace the CAB.
Perform ABS VERIFICATION TEST - VER 1.
No
→
Replace the Left Front Wheel Speed Sensor.
Perform ABS VERIFICATION TEST - VER 1.
24
BRAKES (CAB)
LEFT FRONT SENSOR SIGNAL FAILURE —
Continued
TEST
ACTION
APPLICABILITY
8
Turn the ignition off.
Visually inspect wheel speed sensor.
Visually inspect tone wheel.
Visually inspect wiring harness.
Visually inspect brakes for locking up due to lining contamination or overheating.
Inspect all Components for defects which may cause a Signal DTC to set.
Is any Component Damaged?
All
Yes
→
Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No
→
Test Complete.
25
BRAKES (CAB)
LEFT FRONT SENSOR SIGNAL FAILURE —
Continued
Symptom:
LEFT REAR SENSOR CIRCUIT FAILURE
When Monitored and Set Condition:
LEFT REAR SENSOR CIRCUIT FAILURE
When Monitored:
Ignition on. The CAB monitors the wheel speed circuit every 7
milliseconds (ms).
Set Condition:
If the CAB detects an open or shorted wheel speed sensor circuit, the
Diagnostic Trouble Code (DTC) will set.
POSSIBLE CAUSES
LEFT REAR WHEEL SPEED SENSOR OR CONNECTOR DAMAGE
LEFT REAR WHEEL SPEED SENSOR (+) CIRCUIT SHORTED TO GROUND
LEFT REAR WHEEL SPEED SENSOR (-) CIRCUIT SHORTED TO GROUND
LEFT REAR WHEEL SPEED SENSOR - SHORT TO GROUND
CAB - INTERNAL SHORT OR OPEN
LEFT REAR WHEEL SPEED SENSOR (+) CIRCUIT OPEN
LEFT REAR WHEEL SPEED SENSOR (-) CIRCUIT OPEN
LEFT REAR WHEEL SPEED SENSOR (+) CIRCUIT SHORTED TO VOLTAGE
LEFT REAR WHEEL SPEED SENSOR (-) CIRCUIT SHORTED TO VOLTAGE
LEFT REAR WHEEL SPEED SENSOR CIRCUITS SHORT TOGETHER
LEFT REAR WHEEL SPEED SENSOR RESISTANCE OUT OF SPECIFICATION
INTERMITTENT CIRCUIT DTC
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, read DTC’s.
With the DRBIII
t, erase DTC’s.
Turn the ignition off.
Turn the ignition on.
With the DRBIII
t, read DTC’s.
Does the DRBIII
t display LR Wheel Speed Sensor Circuit Failure DTC?
All
Yes
→
No
→
2
Turn the ignition off.
Inspect the Left Rear Wheel Speed Sensor and Connector.
Is the Sensor or Connector Damaged?
All
Yes
→
Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No
→
26
BRAKES (CAB)
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