Jeep Wrangler TJ. Manual — part 54
Be careful when performing electrical tests so as
to prevent accidental shorting of terminals. Such
mistakes can damage fuses or components. Also, a
second code could be set, making diagnosis of the
original problem more difficult.
4.3.2
ROAD TESTING A COMPLAINT
VEHICLE
Some complaints will require a test drive as part
of the repair verification procedure. The purpose of
the test drive is to try to duplicate the diagnostic
code or symptom condition.
NOTE: After the repair of pump or speed
signal DTC’s, the vehicle must be driven at 25
km/h (15 mph) to clear the DTC from the CAB.
WARNING:
BEFORE
ROAD
TESTING
A
VEHICLE,
BE
SURE
THAT
ALL
COMPONENTS
ARE
REASSEMBLED.
DURING THE TEST DRIVE, DO NOT TRY TO
READ
THE
DRBIII
T
SCREEN
WHILE
IN
MOTION. DO NOT HANG THE DRB FROM
THE REAR VIEW MIRROR OR OPERATE IT
YOURSELF.
HAVE
AN
ASSISTANT
AVAILABLE TO OPERATE THE DRBIII
T
.
4.4
DIAGNOSIS
1. Your diagnostic test procedure must begin with a
thorough visual inspection of the ABS for dam-
aged components or disconnected connectors.
The brake lamps must be operational prior to
continuing.
2. Connect the DRBIII
t to the data link connector
located under the dash. If the DRBIII
t does not
power up, check the power and ground supplies
to the connector.
3. Select ‘‘Antilock Brakes’’. Turn the ignition on. If
the DRBIII
t displays ‘‘No Response’’, perform
the proper test.
4. Read and record all ABS diagnostic trouble
codes. If the ‘‘CAB Power Feed Circuit’’ trouble
code is present, it must be repaired prior to
addressing any other DTC’s. If any additional
codes are present, proceed to the appropriate
test.
5. If there are no diagnostic trouble codes present,
select ‘‘Inputs/Outputs’’ and read the brake
switch input as you press and release the brake
pedal. If the display does not match the state of
the pedal, perform the appropriate test. Read the
‘‘G-Switch’’ status, with the vehicle on a level
surface, both switches should read ‘‘CLOSED’’. If
the status is not correct, perform the appropriate
test. If a problem with the ABS warning indica-
tor exists, refer to the appropriate test.
6. If no other problem are found, it will be neces-
sary to road test the vehicle. THE DRBIII
t
MUST NOT BE CONNECTED TO THE
DATA LINK CONNECTOR WHEN ROAD
TESTING FOR PROPER ANTILOCK OP-
ERATION. THE SYSTEM IS DISABLED
WHILE IN DIAGNOSTIC MODE. Perform
several antilock stops from above 50 Km/h (30
mph) and then repeat steps 2, 3, and 4. If any
diagnostic trouble codes are present, proceed to
the appropriate test.
7. The following conditions should be considered
‘‘NORMAL’’ operation, and no repairs should be
attempted to correct them.
– Brake pedal feedback during an ABS stop
(clicking, vibrating)
– Clicking, groaning or buzzing at 10 Km/h (6
mph) (drive off self test)
– Groaning noise during an ABS stop
– Slight brake pedal drop and pop noise when
ignition is initially turned on
– Brake pedal ratcheting down at the end of an
ABS stop
8. If the complaint is “ABS cycling” at the end of a
stop at low speeds, it may be caused by a
marginal wheel speed sensor signal. The sensor
air gap, tone wheel condition, and/or brakes
hanging up are possible causes of this condition.
9. After a road test in which no problems were
found, refer to any Technical Service Bulletins
that may apply.
5.0
REQUIRED TOOLS AND
EQUIPMENT
DRBIII
t (diagnostic read-out box)
jumper wires
ohmmeter
voltmeter
test lamp
7
GENERAL INFORMATION
6.0
GLOSSARY OF TERMS
ABS
antilock brake system
AC
alternating current
BCM
Body Control Module
CAB
controller antilock brake
CCD
Chrysler Collision Detection
DC
direct current
DLC
data link connector
DRBIII
t
diagnostic read-out box
DTC
diagnostic trouble code
HCU
hydraulic control unit
HZ
Hertz
JBLK
junction block
JTEC
Jeep and Truck Engine Controller
LF
left front
LR
left rear
PCM
Powertrain Control Module
PDC
power distribution center
P/M
pump motor
RF
right front
RR
right rear
SCI
Serial Communication Interface
SOL
Solenoid
WSS
wheel speed sensor
8
GENERAL INFORMATION
7.0
DIAGNOSTIC INFORMATION AND
PROCEDURES
9
Symptom:
CAB POWER FEED CIRCUIT
When Monitored and Set Condition:
CAB POWER FEED CIRCUIT
When Monitored:
Ignition on. The CAB monitors the Fused B(+) circuit at all times for
proper system voltage.
Set Condition:
If the Fused B(+) voltage is missing when the CAB detects that an internal
main driver is not
9on9, the Diagnostic Trouble Code (DTC) is set.
POSSIBLE CAUSES
INTERMITTENT DTC
B(+) CIRCUIT SHORTED TO GROUND
BLOWN FUSE - FUSED B(+) CIRCUIT
CAB - FUSED B(+) CIRCUIT SHORTED TO GROUND
FUSED B(+) CIRCUIT OPEN
NO B+ SUPPLY TO FUSE
CAB - FUSED B(+) CIRCUIT OPEN
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, erase DTC’s.
Turn the ignition off.
Turn the ignition on.
Drive the vehicle above 25 km/h (15 mph) for at least 10 seconds.
Stop the vehicle.
With the DRBIII
t, read DTC’s.
Does the DRBIII
t display CAB Power Feed Circuit DTC present right now?
All
Yes
→ Go To 2
No
→ Go To 9
2
Turn the ignition off.
Remove and Inspect Fuse 12 in the PDC.
Is the Fuse blown?
All
Yes
→ Go To 3
No
→ Go To 6
10
BRAKES (CAB)
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