2000 DODGE NEON light

CONDITION POSSIBLE CAUSES CORRECTION
PEDAL PULSATES/SURGES
DURING BRAKING1. Rear brake drum out of round or
disc brake rotor has excessive
thickness variation.1. Isolate condition as rear or front.
Reface or replace brake drums or rotors
as necessary.
PEDAL IS SPONGY 1. Air in brake lines. 1. Bleed brakes.
2. Power brake booster runout
(vacuum assist).2. Check booster vacuum hose and
engine tune for adequate vacuum supply.
Refer to power brake booster in the
diagnosis and testing section.
PREMATURE REAR WHEEL
LOCKUP1. Contaminated brake shoe linings. 1. Inspect and clean, or replace shoes.
Repair source of contamination.
2. Inoperative proportioning valve
(non-ABS vehicles only).2. Test proportioning valves folowing
procedure listed in diagnosis and testing
section. Replace valves as necessary.
3. ABS EBD not functioning. 3. Refer to the ABS section and Chassis
Diagnostic Procedures manual.
4. Improper power brake booster
assist.4. Refer to power brake booster in the
diagnosis and testing section.
STOP LAMPS STAY ON 1. Brake lamp switch out of
adjustment.1. Adjust brake lamp switch.
2. Brake pedal binding. 2. Inspect and replace as necessary.
3. Obstruction in pedal linkage. 3. Remove obstruction.
4. Power Brake Booster not allowing
pedal to return completely.4. Replace power brake booster.
VEHICLE PULLS TO RIGHT
OR LEFT ON BRAKING1. Frozen brake caliper piston. 1. Replace frozen piston or caliper. Bleed
brakes.
2. Contaminated brake shoe lining. 2. Inspect and clean, or replace shoes.
Repair source of contamination.
3. Pinched brake lines. 3. Replace pinched line.
4. Leaking piston seal. 4. Replace piston seal or brake caliper.
5. Suspension problem. 5. Refer to the Suspension group.
PARKING BRAKE -
EXCESSIVE HANDLE
TRAVEL1. Rear brakes out of adjustment. 1. Adjust rear drum brake shoes, or rear
parking brake shoes on vehicles with rear
disc brakes.
POWER BRAKE BOOSTER
BASIC TEST
(1) With engine off, depress and release the brake
pedal several times to purge all vacuum from the
power brake booster.
(2) Depress and hold the pedal with light effort (15
to 25 lbs. pressure), then start the engine.
The pedal should fall slightly, then hold. Less effort
should be needed to apply the pedal at this time. If
the pedal fell as indicated, perform the VACUUM
LEAK TEST listed after the BASIC TEST. If thepedal did not fall, continue on with this BASIC
TEST.
(3) Disconnect the vacuum hose on the side of the
vacuum check valve that leads to the speed control,
then connect a vacuum gauge to the open vacuum
port on the valve.
(4) Start the engine.
(5) When the engine is at warm operating temper-
ature, allow it to idle and check the vacuum at the
gauge.
PLBRAKES 5 - 11
DIAGNOSIS AND TESTING (Continued)

If the vacuum supply is 12 inches Hg (40.5 kPa) or
more, the power brake booster is defective and must
be replaced. If the vacuum supply is below 12 inches,
continue on with this BASIC TEST.
(6) Shut off the engine.
(7) Connect the vacuum gauge to the vacuum ref-
erence port on the engine intake manifold.
(8)
Start the engine and observe the vacuum gauge.
If the vacuum is still low, check the engine tune
and repair as necessary. If the vacuum is above 12
inches, the hose or check to the booster has a restric-
tion or leak.
Once an adequate vacuum supply is obtained,
repeat the BASIC TEST.
VACUUM LEAK TEST
(1) Disconnect the vacuum hose on the side of the
power brake booster vacuum check valve that leads
to the speed control, then connect a vacuum gauge to
the open vacuum port on the valve.
(2) Remove the remaining hose on the vacuum
check valve that is not the vacuum supply hose com-
ing from the intake manifold. Cap off the open port
on the check valve.
(3) Start the engine.
(4) Allow the engine to warm up to normal operat-
ing temperature and engine idle.
(5) Using vacuum line pliers, close off the vacuum
supply hose near the booster and observe the vacuum
gauge.
If the vacuum drop exceeds 1.0 inch Hg (3.3 kPa)
in one minute, repeat the above steps to confirm the
reading. The vacuum loss should be less than 1.0
inch Hg in one minute time span. If the loss is more
than 1.0 inch Hg, replace the power brake booster. If
it is not, continue on with this test.
(6) Remove the pliers from the hose temporarily.
(7) Apply light effort (approximately 15 lbs. of
force) to the brake pedal and hold the pedal steady.
Do not move the pedal once the pressure is applied
or the test results may vary.
(8) Have an assistant reattach the pliers to the
vacuum supply hose.
(9) Allow 5 seconds for stabilization, then observe
the vacuum gauge.
If the vacuum drop exceeds 3.0 inches Hg (10 kPa)
in 15 seconds, repeat the above steps to confirm the
reading. The vacuum loss should be less than 3.0
inches Hg in 15 seconds time span. If the loss is
more than 3.0 inches Hg, replace the power brake
booster. If it is not, the booster is not defective.
DRUM BRAKE AUTOMATIC ADJUSTER
To properly test the drum brake automatic
adjuster, the aide of a helper inside the vehicle to
apply the brakes will be necessary.(1) Raise the vehicle. Refer to HOISTING in the
LUBRICATION AND MAINTENANCE group for the
proper lifting procedure.
(2) Remove the access plug from the rear adjust-
ment slot in each brake support plate.
(3) Insert a thin screwdriver in the adjustment
slot and push back the adjustment lever. With the
lever in this position, back the star wheel adjustment
off approximately 10 notches. This will eliminate the
possibility that the brake is at full adjustment, and
can be adjusted no further.
(4)
Remove the screwdriver from the adjustment slot.
(5) Watch the star wheel through the adjustment
slot, while a helper applies the brake pedal. As the
brake shoes apply, the adjustment lever should move
downward, turning the star wheel. A definite rotation
of the adjuster star wheel can be observed if the
automatic adjuster is working properly.
If the star wheel does not move as indicated, the
brake drum needs to be removed and further inspec-
tion of the rear brakes is necessary.
(6) If the star wheel is operating properly, readjust
the brakes. Refer to ADJUSTMENTS in this section
of this service manual group.
(7) Reinstall the adjustment slot access plug.
(8) Lower the vehicle.
BRAKE ROTOR
Any servicing of the rotor requires extreme care to
maintain the rotor within service tolerances to
ensure proper brake action.
Excessive runout or wobble in a rotor can increase
pedal travel due to piston knock-back. This increases
guide pin sleeve wear due to the tendency of the cal-
iper to follow the rotor wobble.
When diagnosing a brake noise or pulsation, the
machined disc braking surface should be checked and
inspected.
BRAKING SURFACE INSPECTION
Light braking surface scoring and wear is accept-
able. If heavy scoring or warping is evident, the rotor
must be refaced or replaced. Refer to SERVICE PRO-
CEDURES in this section of this group for informa-
tion on brake rotor machining.
Excessive wear and scoring of the rotor can cause
improper lining contact on the rotor's braking sur-
face. If the ridges on the rotor are not removed before
new brake shoes are installed, improper wear of the
shoes will result.
If a vehicle has not been driven for a period of
time, the rotor's braking surface will rust in the
areas not covered by the brake shoes at that time.
Once the vehicle is driven, noise and chatter from
the disc brakes can result when the brakes are
applied.
5 - 12 BRAKESPL
DIAGNOSIS AND TESTING (Continued)

(6) Install the pin on the parking brake lever into
hole in rear brake shoe assembly (Fig. 86).
(7) Install both brake shoe-to-brake support plate
hold down pins and clips (Fig. 81).
(8) Install the lower brake shoe-to-anchor plate
return spring (Fig. 82).
(9) Install the automatic adjustment lever on the
leading brake shoe (Fig. 80).(10) Install the automatic adjustment lever-to-
brake shoe spring (Fig. 79).
(11) Adjust the brake shoes out until the drum
lightly drags on the shoes when it is installed. Do not
over-adjust the brakes.
(12) Install the brake drum (Fig. 78).
(13) Repeat the above procedure to the rear brakes
on the other side of the vehicle.
(14) Install the tire and wheel assemblies. Tighten
the wheel mounting nuts to a torque of 135 N´m (100
ft. lbs.).
(15) Adjust the rear brake shoes. Refer to
ADJUSTMENTS in this section of this service man-
ual group.
(16) Lower the vehicle.
(17) Road test vehicle stopping in both the forward
and reverse directions. The automatic adjuster will
continue to adjust the brakes during the road test of
the vehicle.
BRAKE DRUM (REAR)
REMOVAL
(1) Raise the vehicle. Refer to HOISTING in the
LUBRICATION AND MAINTENANCE group for the
proper lifting procedure.
(2) Remove the rear tire and wheel assembly from
the vehicle.
(3) Remove the brake drum retaining clips (if
equipped) (Fig. 87).
Fig. 85 Shoe Contact Areas on Support Plate
Fig. 86 Parking Brake Lever Pin Retaining Clip
Installation
1 ± BRAKE SHOE ASSEMBLY
2 ± RETAINING CLIP
3 ± SCREWDRIVER
4 ± PARK BRAKE LEVER
5 ± PARK BRAKE LEVER PIN
Fig. 87 Drum Brakes
1 ± DUST CAP
2 ± NUT
3 ± DRUM
4 ± HUB AND BEARING
5 ± WHEEL CYLINDER
6 ± SEAL
7 ± SUPPORT PLATE
8 ± BRAKE SHOES
9 ± RETAINER CLIP
PLBRAKES 5 - 45
REMOVAL AND INSTALLATION (Continued)

CALIPER PISTON AND SEALS
CALIPER PISTON REMOVAL
WARNING: UNDER NO CONDITION SHOULD HIGH
PRESSURE AIR EVER BE USED TO REMOVE A PIS-
TON FROM A CALIPER BORE. PERSONAL INJURY
COULD RESULT FROM SUCH A PRACTICE.
NOTE: The safest way to remove the piston from
the caliper bore is to use the hydraulic pressure of
the vehicle's brake system.
(1) Following the removal procedure in DISC
BRAKE SHOES found in this section, remove the
caliper from the brake rotor and hang the assembly
on a wire hook away from rotor and body of the vehi-
cle so brake fluid cannot get on these components.
Remove the brake shoes, and place a small piece of
wood between the piston and caliper fingers.
(2) Carefully depress the brake pedal to hydrauli-
cally push piston out of its bore. Once completed,
apply and hold down the brake pedal to any position
beyond the first inch of pedal travel using a brake
pedal holding tool. This will prevent the fluid in the
master cylinder reservoir from completely draining
out.(3) Disconnect the brake fluid flex hose from the
caliper assembly and remove it from the vehicle.
CALIPER SEAL REMOVAL
CAUTION: Do not use excessive force when clamp-
ing caliper in vise. Excessive vise pressure will
cause bore distortion.
(1) To disassemble the caliper, mount it in a vise
equipped with protective jaws.
(2) Remove the piston dust boot from the caliper
and discard (Fig. 118).
NOTE: Do not use a screw driver or other metal
tool for seal removal. Using such tools can scratch
the bore or leave burrs on the seal groove edges.
(3) Using a soft tool such as a plastic trim stick,
work the piston seal out of its groove in caliper pis-
ton bore (Fig. 119). Discard the old seal.
(4) Clean the piston bore and drilled passage ways
using alcohol or a suitable solvent. Wipe it dry using
only a lint-free cloth.
(5) Inspect the piston bore for scoring or pitting.
Bores that show light scratches or corrosion can usu-
ally be cleared of the light scratches or corrosion
using crocus cloth. Bores that have deep scratches or
scoring should be honed. Use Caliper Hone, Special
Tool C-4095, or the equivalent to hone the bore. Do
Fig. 117 Correctly Installed Guide Pin Sleeve And
Bushing
1 ± CALIPER
2 ± BUSHING
3 ± SLEEVE
Fig. 118 Removing Caliper/Piston Dust Boot
1 ± CALIPER
2 ± SCREWDRIVER
3 ± BOOT
PLBRAKES 5 - 57
DISASSEMBLY AND ASSEMBLY (Continued)

(4) Insert a brake adjustment tool, or a screw-
driver, through the adjusting hole in support plate
and against the star wheel of the adjuster screw.
Move the handle of tool downward to adjust the
brake drag. Rotate the tire and wheel assembly while
adjusting the adjuster screw. Continue to adjust the
shoes until a slight drag is noticed when the tire and
wheel assembly is rotated.
NOTE: In the event the brake shoes are over-ad-
justed, the adjuster can be backed off using the fol-
lowing step. If not, proceed to step 6.
(5) If the shoes are in the over-adjusted position,
insert a thin screwdriver into brake adjusting hole
and push back the adjusting lever out of engagement
with star wheel (Fig. 127). Take care not to bend the
adjusting lever. While holding the adjusting lever out
of engagement with star wheel, back off the star
wheel until the tire and wheel assembly is free to
turn without dragging. Repeat the adjustment proce-
dure.
(6) Install adjusting hole rubber plug (Fig. 126).
(7) Repeat the above adjustment procedure to the
other side brakes.
(8) Apply and release the park brake lever one
time after the adjustment process is completed so the
parking brakes can readjust themselves to the new
brake shoe adjustment.
PARKING BRAKE SHOES (REAR DISC BRAKES)
NOTE: The parking brake shoes used in the drum-
in-hat park brake system do not automatically
adjust to compensate for brake shoe lining wear.Therefore, it is necessary to manually adjust the
parking brake shoes.
(1) Verify the parking brake lever is in the
released position.
(2) Raise the vehicle. Refer to HOISTING in the
LUBRICATION AND MAINTENANCE group for the
proper lifting procedure.
(3) Remove the rubber plug from the adjusting
hole in the disc brake caliper adapter.
(4) Adjust the parking brakes. Use the first bullet
point for the adjustment of the left side parking
brake shoes. Use the second bullet point for the
adjustment of the right side parking brake shoes.
²Insert a medium size screwdriver through
adjustment hole in the left backing plate. Position
the screwdriver against the star wheel on the park-
ing brake shoe adjuster. Using the screwdriver,
rotate the star wheel downward until a slight drag is
noticed when turning the rear tire and wheel assem-
bly. Then, using the screwdriver, slowly rotate the
star wheel upward, backing off the adjuster, just
enough to allow the rear tire and wheel assembly to
rotate without the parking brake shoes dragging. Do
not back off the adjuster star wheel more than two
clicks past the point of no drag. The parking brake
shoe-to-drum clearance is now properly set.
²Insert a medium size screwdriver through
adjustment hole in the right backing plate. Position
the screwdriver against the star wheel on the park-
ing brake shoe adjuster. Using the screwdriver,
rotate the star wheel upward until a slight drag is
noticed when turning the rear tire and wheel assem-
bly. Then, using the screwdriver, slowly rotate the
star wheel downward, backing off the adjuster, just
enough to allow the rear tire and wheel assembly to
rotate without the parking brake shoes dragging. Do
not back off the adjuster star wheel more that two
clicks past the point of no drag. The parking brake
shoe-to-drum clearance is now properly set.
(5) Install the rubber plug in the adjusting holes of
the disc brake caliper adapter.
(6) Lower the vehicle until the rear tires are just
clearing the floor.
(7) Reach inside the vehicle and fully apply and
release the park brakes two times after adjusting the
parking brake shoes.
(8) With the parking brake lever in the fully
applied position, attempt to hand rotate each rear
tire and wheel assembly to ensure that the parking
brake shoes are working.
(9) With the parking brake lever in the released
position, hand rotate each rear tire and wheel assem-
bly to ensure that the parking brake shoes are not
dragging.
Fig. 127 Backing Off Brake Adjuster Screw
1 ± MEDIUM SCREWDRIVER
2 ± BRAKE ADJUSTING HOLE
3 ± THIN SCREWDRIVER OR WELDING ROD
5 - 62 BRAKESPL
ADJUSTMENTS (Continued)

NOISE AND BRAKE PEDAL FEEL
During ABS braking, some brake pedal movement
may be felt. In addition, ABS braking will create
ticking, popping, or groaning noises heard by the
driver. This is normal and is due to pressurized fluid
being transferred between the master cylinder and
the brakes. If ABS operation occurs during hard
braking, some pulsation may be felt in the vehicle
body due to fore-and-aft movement of the suspension
as brake pressures are modulated.
At the end of an ABS stop, ABS is turned off when
the vehicle is slowed to a speed of 3±4 mph. There
may be a slight brake pedal drop anytime that the
ABS is deactivated, such as at the end of the stop
when the vehicle speed is less than 3 mph or during
an ABS stop where ABS is no longer required. These
conditions exist when a vehicle is being stopped on a
road surface with patches of ice, loose gravel, or sand
on it. Also, stopping a vehicle on a bumpy road sur-
face activates ABS because of the wheel hop caused
by the bumps.
TIRE NOISE AND MARKS
Although the ABS system prevents complete wheel
lockup, some wheel slip is desired in order to achieve
optimum braking performance. Wheel slip is defined
as follows: 0 percent slip means the wheel is rolling
freely and 100 percent slip means the wheel is fully
locked. During brake pressure modulation, wheel slip
is allowed to reach up to 25±30 percent. This means
that the wheel rolling velocity is 25±30 percent less
than that of a free rolling wheel at a given vehicle
speed. This slip may result in some tire chirping,
depending on the road surface. This sound should not
be interpreted as total wheel lockup.
Complete wheel lockup normally leaves black tire
marks on dry pavement. The ABS will not leave dark
black tire marks since the wheel never reaches a
fully locked condition. However, tire marks may be
noticeable as light patched marks.
START-UP CYCLE
When the ignition is turned on, a popping sound
and a slight brake pedal movement may be noticed.
The ABS warning lamp will also be on for up to 5
seconds after the ignition is turned on. When the
vehicle is first driven off, a humming may be heard
or felt by the driver at approximately 20±40 kph
(12±25 mph). All of these conditions are a normal
function of ABS as the system is performing a diag-
nosis check.
PREMATURE ABS CYCLING
Symptoms of premature ABS cycling include: click-
ing sounds from the solenoid valves; pump/motor
running; and pulsations in the brake pedal. Prema-ture ABS cycling can occur at any braking rate of the
vehicle and on any type of road surface. Neither the
red BRAKE warning lamp, nor the amber ABS warn-
ing lamp, illuminate and no fault codes are stored in
the CAB.
Premature ABS cycling is a condition that needs to
be correctly assessed when diagnosing problems with
the antilock brake system. It may be necessary to use
a DRB scan tool to detect and verify premature ABS
cycling.
Check the following common causes when diagnos-
ing premature ABS cycling: damaged tone wheels;
incorrect tone wheels; damaged steering knuckle
wheel speed sensor mounting bosses; loose wheel
speed sensor mounting bolts; excessive tone wheel
runout; or an excessively large tone wheel-to-wheel
speed sensor air gap. Give special attention to these
components when diagnosing a vehicle exhibiting
premature ABS cycling.
After diagnosing the defective component, repair or
replace it as required. When the component repair or
replacement is completed, test drive the vehicle to
verify that premature ABS cycling has been cor-
rected.
ANTILOCK BRAKE SYSTEM COMPONENTS
The following is a detailed description of the
antilock brake system components. For information
on servicing base brake system components used in
conjunction with these components, see the BASE
BRAKE SYSTEM found at the beginning of this ser-
vice manual group.
MASTER CYLINDER
A vehicle equipped with ABS uses a different mas-
ter cylinder than a vehicle that is not equipped with
ABS. Vehicles equipped with ABS use a center port
master cylinder with only two outlet ports (Fig. 1).
The brake tubes from the primary and secondary
outlet ports on the master cylinder go directly to the
integrated control unit (ICU).
The master cylinder mounts to the power brake
booster in the same manner a non-ABS master cylin-
der does.
INTEGRATED CONTROL UNIT (ICU)
The hydraulic control unit (HCU) and the control-
ler antilock brake (CAB) used with this antilock
brake system are combined (integrated) into one
unit, which is called the integrated control unit (ICU)
(Fig. 2). The ICU is located on the driver's side of the
vehicle, and is mounted to the left front frame rail
below the master cylinder (Fig. 1).
5 - 66 BRAKESPL
DESCRIPTION AND OPERATION (Continued)

DIAGNOSIS AND TESTING
SERVICE WARNINGS AND CAUTIONS
The ABS uses an electronic control module, the
CAB. This module is designed to withstand normal
current draws associated with vehicle operation.
Care must be taken to avoid overloading the CAB
circuits.
CAUTION: In testing for open or short circuits, do
not ground or apply voltage to any of the circuits
unless instructed to do so for a diagnostic proce-
dure.
CAUTION: These circuits should only be tested
using a high impedance multi-meter or the DRB
scan tool as described in this section. Power
should never be removed or applied to any control
module with the ignition in the ON position. Before
removing or connecting battery cables, fuses, or
connectors, always turn the ignition to the OFF
position.
CAUTION: Use only factory wiring harnesses. Do
not cut or splice wiring to the brake circuits. The
addition of after-market electrical equipment (car
phone, radar detector, citizen band radio, trailer
lighting, trailer brakes, etc.) on a vehicle equipped
with antilock brakes may affect the function of the
antilock brake system.
ABS GENERAL DIAGNOSTICS INFORMATION
This section contains information necessary to
diagnose the antilock brake system. Specifically, this
section should be used to help diagnose conditions
which result in any of the following:
(1) amber ABS warning lamp turned on.
(2) brakes lock-up on hard application.
Diagnosis of base brake conditions that are obvi-
ously mechanical in nature should be directed to
BASE BRAKE SYSTEM at the beginning of this
group.
Many ABS conditions judged to be a problem by
the driver may be normal operating conditions. See
ABS OPERATION in the DESCRIPTION AND
OPERATION section of this group to become famil-
iarized with the normal characteristics of this
antilock brake system.
ABS WIRING DIAGRAM INFORMATION
During the diagnosis and testing of the antilock
brake system it may become necessary to reference
the wiring diagrams covering the antilock brake sys-
tem and its components. For wiring diagrams refer to
GROUP 8W of this service manual. It will provide
you with the wiring diagrams and the circuit descrip-
tion and operation information covering the antilock
brake system.
ABS VEHICLE TEST DRIVE
Most ABS complaints will require a test drive to
properly duplicate and diagnose the condition.
WARNING: CONDITIONS THAT RESULT IN TURN-
ING ON THE RED BRAKE WARNING LAMP MAY
INDICATE REDUCED BRAKING ABILITY.
Before test driving a brake complaint vehicle, note
whether the red BRAKE warning lamp, amber ABS
warning lamp, or both are turned on. If it is the red
BRAKE warning lamp, there is a brake hydraulic
problem that must be corrected before driving the
vehicle. Refer to the BASE BRAKE SYSTEM for
diagnosis of the red BRAKE warning lamp. If the red
brake warning lamp is illuminated, there is also a
possibility that there is an ABS problem and the
amber ABS warning lamp is not able to illuminate,
so the MIC turns on the red Brake warning lamp by
default.
If the amber ABS warning lamp is on, test drive
the vehicle as described below. While the amber ABS
warning lamp is on, the ABS is not functional. The
ability to stop the car using the base brake system
should not be affected.
If a functional problem of the ABS is determined
while test driving the vehicle, refer to the Chassis
Diagnostic Procedures manual.
(1) Turn the key to the OFF position and then
back to the ON position. Note whether the amber
ABS warning lamp continues to stay on. If it does,
refer to the diagnostic manual.
(2) If the amber ABS warning lamp goes out, shift
into gear and drive the car to a speed of 20 kph (12
mph) to complete the ABS start-up and drive-off
cycles (see ABS ELECTRONIC DIAGNOSIS). If at
this time the amber ABS warning lamp comes on,
refer to the diagnostic manual.
(3) If the amber ABS warning lamp remains out,
drive the vehicle a short distance. Accelerate the
vehicle to a speed of at least 40 mph. Bring the vehi-
cle to a complete stop, braking hard enough to cause
the ABS to cycle. Again accelerate the vehicle past 25
mph. Refer to the diagnostic manual for further test-
ing of the antilock brake system.
5 - 74 BRAKESPL

ABS ELECTRONIC DIAGNOSIS
The following information is presented to give the
technician a general background on the diagnostic
capabilities of the ABS system. Complete electronic
diagnosis of the ABS system used on this vehicle is
covered in the Chassis Diagnostic Procedures manual.
Electronic diagnosis of the ABS system used on
this vehicle is performed using the DRBIIItscan
tool. The vehicle's scan tool diagnostic connector is
located under the steering column lower cover, to the
left side of the steering column (Fig. 10).
ABS SELF-DIAGNOSIS
The ABS system is equipped with a self-diagnosis
capability, which may be used to assist in the isola-
tion of ABS faults. The features are described below.
START-UP CYCLE
The self-diagnosis ABS start-up cycle begins when
the ignition switch is turned to the ON position.
Electrical checks are completed on ABS components,
including the CAB, solenoid continuity, and the relay
system operation. During this check the amber ABS
warning lamp is turned on for approximately 5 sec-
onds and the brake pedal may emit a popping sound,
moving slightly when the solenoid valves are
checked.
DRIVE-OFF CYCLE
The first time the vehicle is set in motion after an
ignition off/on cycle, the drive-off cycle occurs. This
cycle is performed when the vehicle reaches a speed
of approximately 20 kph (12 mph.).²The pump/motor is briefly activated to verify
function. When the pump/motor is briefly activated, a
whirling or buzzing sound may be heard by the
driver. This sound is normal, indicating the pump/
motor is running.
²The wheel speed sensor output correct operating
range is verified.
ONGOING TESTS
While the system is operating, these tests are per-
formed on a continuous basis:
²solenoid continuity
²wheel speed sensor continuity
²wheel speed sensor output
DIAGNOSTIC TROUBLE CODES (DTC's)
Diagnostic trouble codes (DTC's) are kept in the
controller's memory until either erased by the techni-
cian using the DRB, or erased automatically after
3500 miles or 255 ignition key cycles, whichever
occurs first. DTC's are retained by the controller
even if the ignition is turned off or the battery is dis-
connected. More than one DTC can be stored at a
time. When accessed, the number of occurrences
(ignition key cycles) and the DTC that is stored are
displayed. Most functions of the CAB and the ABS
system can be accessed by the technician for testing
and diagnostic purposes using the DRB.
LATCHING VERSUS NON-LATCHING DIAGNOSTIC TROUBLE
CODES
Some DTC's detected by the CAB are ªlatchingº
codes. The DTC is latched and ABS braking is dis-
abled until the ignition switch is reset. Thus, ABS
braking is non-operational even if the original DTC
has disappeared. Other DTC's are non-latching. Any
warning lamps that are turned on are only turned on
as long as the DTC condition exists; as soon as the
condition goes away, the amber ABS warning lamp is
turned off, although, in most cases, a DTC is set.
INTERMITTENT DIAGNOSTIC TROUBLE CODES
As with virtually any electronic system, intermit-
tent electrical problems in the ABS system may be
difficult to accurately diagnose. Most intermittent
electrical problems are caused by faulty electrical
connections or wiring. A visual inspection should be
done before trying to diagnose or service the antilock
brake system; this will eliminate unnecessary diag-
nosis and testing time. Perform a visual inspection
for loose, disconnected, damaged, or misrouted wires
or connectors; include the following components and
areas of the vehicle in the inspection.
(1) Inspect fuses in the power distribution center
(PDC) and the wiring junction block. Verify that all
fuses are fully inserted into the PDC and wiring
Fig. 10 ABS System Diagnostic Connector Location
1 ± DRIVER AIRBAG MODULE
2 ± PASSENGER AIRBAG MODULE
3 ± DATA LINK CONNECTOR
PLBRAKES 5 - 75
DIAGNOSIS AND TESTING (Continued)