4.3 WARNINGS
4.3.1 VEHICLE DAMAGE WARNINGS
Before disconnecting any control module, make
sure the ignition is ‘‘off’’. Failure to do so could
damage the module.
When testing voltage or continuity at any control
module, use the terminal side (not the wire end) of
the connector. Do not probe a wire through the
insulation, this will damage it and eventually cause
it to fail because of corrosion.
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.
WARNING: BEFORE ROAD TESTING A
VEHICLE, BE SURE THAT ALL
COMPONENTS ARE REASSEMBLED.
DURING THE TEST DRIVE, DO NOT TRY TO
READ THE DRB SCREEN WHILE IN MOTION.
DO NOT HANG THE DRBIIIT FROM THE
REAR VIEW MIRROR OR OPERATE IT
YOURSELF. HAVE AN ASSISTANT
AVAILABLE TO OPERATE THE DRBIIIT.
4.4 DIAGNOSIS
1. Your diagnostic test proceduremust beginwith a
thorough visual inspection of the system in ques-
tion for damaged components or disconnected
connectors. For ABS the brake lamps must be
operational prior to continuing.
2. Connect the DRBIIIt to the data link connector,
which is located under the dash to the left of the
steering column. If the DRBIIIt does not power
up, check the power and ground supplies to the
connector.
3. Turn the ignition on. Select the system in ques-
tion. If the DRBIIIt displays “No Response”
condition you must diagnose that first.
4. Read and record all diagnostic trouble codes. For
ABS if the “CAB Power Feed Circuit” diagnostic
trouble code is present, it must be repaired prior
to addressing any other DTC’s. If any additional
DTC’s are present, proceed to the appropriate
test by locating the matching test in the Table of
Contents and begin to diagnose the symptom.
5. For ABS if there are no diagnostic trouble codes
present, identify the customer complaint. Select
“Inputs/Outputs” and read the brake switch in-
put as you press and release the brake pedal. If
the display does not match the state of the pedal,
diagnose the symptom. If a problem exists with
the amber “ABS” warning indicator or the red
“Brake” indicator exists, diagnose the symptom.
Read the traction control switch input as you
press and release the switch. If the display does
not match the state of the indicator, diagnose the
symptom.
6. If no other problems are found, it will be neces-
sary to road test the vehicle. Perform several
antilock stops from above 50 Km/h (30 mph) and
then repeat step 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 25 Km/h (15
mph) or 40 Km/h (24 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
DRBIIIt (diagnostic read-out box)
jumper wires
ohmmeter
voltmeter
test light
6.0 GLOSSARY OF TERMS
ABS antilock brake system
BCM body control module
6
GENERAL INFORMATION
ProCarManuals.com
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