TONE WHEEL INSPECTION
Carefully inspect tone wheel at the suspected faulty
wheel speed sensor for missing, chipped or broken
teeth, this can cause erratic speed sensor signals.
Tone wheels should show no evidence of contact
with the wheel speed sensors. If contact was made,
determine cause and correct before replacing the
wheel speed sensor.
Excessive runout of the tone wheel can cause
erratic wheel speed sensor signals. Refer to Tone
Wheel Runout in the Specification Section in this sec-
tion of the service manual for the tone wheel runout
specification. Replace driveshaft assembly or rear
hub/bearing assembly if tone wheel runout exceeds
the specification.
Inspect tone wheels for looseness on their mount-
ing surfaces. Tone wheels are pressed onto their
mounting surfaces and should not rotate indepen-
dently from the mounting surface.
Check the wheel speed sensor head alignment to
the tone wheel. Also check the gap between the speed
sensor head and the tone wheel to ensure it is at
specification. Refer to Wheel Speed Sensor Clearance
in the Specification Section in this section of the ser-
vice manual.
BRAKE FLUID CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
If brake fluid is contaminated, drain and thor-
oughly flush system. Replace master cylinder, propor-
tioning valve, caliper seals, wheel cylinder seals,
Antilock Brakes hydraulic unit and all hydraulic
fluid hoses.
TEST DRIVING ABS COMPLAINT VEHICLE
Most ABS complaints will require a test drive as a
part of the diagnostic procedure. The purpose of the
test drive is to duplicate the condition.
NOTE:
Remember conditions that result in the
turning on of the Red BRAKE Warning Lamp may
indicate reduced braking ability. If both the ABS &
BRAKE Warning Lamp come on simultaneously, the
PCI BUS communication is lost. The following pro-
cedure should be used to test drive an ABS com-
plaint vehicle.
Before test driving a brake complaint vehicle, note
whether the Red or Amber Brake Warning Lamp is
turned on. If it is the Red Brake Warning Lamp,
refer to the hydraulic system section in the brake
group of this manual. If the ABS Warning lamp
was/is on, test drive the vehicle as described below, to
verify the complaint. While the ABS Warning Lamp
is on, the ABS is not functional. The standard brake
system and the ability to stop the car may not be
affected if only the ABS Warning Lamp is on.
Discuss with the owner of the vehicle or note any
other electrical problems or conditions that may be
occurring on the vehicle. They may have an effect on
the antilock brake system’s function.
(1) Turn the key to the off position and then back
to the on position. Note whether the ABS Warning
Lamp continues to stay on. If it does, refer to the
diagnostic manual covering the Mark 20 ABS system
for the required test procedures.
(2) If the ABS Warning Lamp goes out, shift into
gear and drive the car to a speed of 20 km/h (12
mph) to complete the ABS start up cycle. If at this
time the ABS Warning Lamp goes on refer to the
Mark 20 Diagnostic Manual.
(3) If the ABS Warning Lamp remains OUT, drive
the vehicle a short distance. During this test drive be
sure that the vehicle achieves at least 40 mph. Brake
to at least one complete stop in an ABS cycle, and
again accelerate to 25 mph.
(4) If a functional problem with the ABS system is
determined while test driving a vehicle, refer to the
diagnostic manual covering the Mark 20 ABS system
for the required test procedures and proper use of the
DRB diagnostic scan tool.
SERVICE PROCEDURES
BRAKE FLUID LEVEL INSPECTION
CAUTION:
Use only Mopar brake fluid or an equiv-
alent from a tightly sealed container. Brake fluid
must conform to DOT 3 specifications. Do not use
petroleum-based fluid because seal damage in the
brake system will result.
For the specific procedure covering the inspection
of the brake fluid level and adding brake fluid to the
reservoir, refer to the Service Adjustments Section in
this group of the service manual.
BLEEDING TEVES MARK 20 HYDRAULIC SYSTEM
The hydraulic system for the base brakes must be
bled anytime air enters the hydraulic system. Air can
enter the hydraulic system for the base brakes due to
the disconnection of brake lines, hoses or any other
hydraulically operated component of the base brake
system. The ABS system, particularly the ICU, should
only be bled when the ICU is replaced or it is removed
from the vehicle. The ICU must also always be bled if
5 - 62
BRAKES
300M
DIAGNOSIS AND TESTING (Continued)