1998 OPEL FRONTERA check engine light

DIFFERENTIAL (REAR 220mm)
4A2A–3
Diagnosis
Many noises that seem to come from the rear axle
actually originate from other sources such as tires, road
surface, wheel bearings, engine, transmission, muffler, or
body drumming. Investigate to find the source of the
noise before disassembling the rear axle. Rear axles, like
any other mechanical device, are not absolutely quiet but
should be considered quiet unless some abnormal noise
is present.
To make a systematic check for axle noise, observe the
following:
1. Select a level asphalt road to reduce tire noise and
body drumming.
2. Check rear axle lubricant level to assure correct level,
and then drive the vehicle far enough to thoroughly
warm up the rear axle lubricant.
3. Note the speed at which noise occurs. Stop the
vehicle and put the transmission in neutral. Run the
engine speed slowly up and down to determine if the
noise is caused by exhaust, muffler noise, or other
engine conditions.
4. Tire noise changes with different road surfaces; axle
noises do not. Temporarily inflate all tires to 344 kPa
(3.5kg/cm
2, 50 psi) (for test purposes only). This will
change noise caused by tires but will not affect noise
caused by the rear axle.
Rear axle noise usually stops when coasting at
speeds under 48 km/h (30 mph); however, tire noise
continues with a lower tone. Rear axle noise usually
changes when comparing pull and coast, but tire
noise stays about the same.
Distinguish between tire noise and rear axle noise by
noting if the noise changes with various speeds or
sudden acceleration and deceleration. Exhaust and
axle noise vary under these conditions, while tire
noise remains constant and is more pronounced at
speeds of 32 to 48 km/h (20 to 30 mph). Further check
for tire noise by driving the vehicle over smooth
pavements or dirt roads (not gravel) with the tires at
normal pressure. If the noise is caused by tires, it will
change noticeably with changes in road surface.
5. Loose or rough front wheel bearings will cause noise
which may be confused with rear axle noise; however,
front wheel bearing noise does not change when
comparing drive and coast. Light application of the
brake while holding vehicle speed steady will often
cause wheel bearing noise to diminish. Front wheel
bearings may be checked for noise by jacking up the
wheels and spinning them or by shaking the wheels to
determine if bearings are loose.
6. Rear suspension rubber bushings and spring
insulators dampen out rear axle noise when correctly
installed. Check to see that there is no link or rod
loosened or metal–to–metal contact.
7. Make sure that there is no metal–to–metal contact
between the floor and the frame.
After the noise has been determined to be in the axle, the
type of axle noise should be determined, in order to make
any necessary repairs.
Gear Noise
Gear noise (whine) is audible from 32 to 89 km/h (20 to 55
mph) under four driving conditions.
1. Driving under acceleration or heavy pull.
2. Driving under load or under constant speed.
3. When using enough throttle to keep the vehicle from
driving the engine while the vehicle slows down
gradually (engine still pulls slightly).
4. When coasting with the vehicle in gear and the throttle
closed. The gear noise is usually more noticeable
between 48 and 64 km/h (30 and 40 mph) and 80 and
89 km/h (50 and 55 mph).
Bearing Noise
Bad bearings generally produce a rough growl or grating
sound, rather than the whine typical of gear noise.
Bearing noise frequently “wow–wows” at bearing rpm,
indicating a bad pinion or rear axle side bearing. This
noise can be confused with rear wheel bearing noise.
Rear Wheel Bearing Noise
Rear wheel bearing noise continues to be heard while
coasting at low speed with transmission in neutral. Noise
may diminish by gentle braking. Jack up the rear wheels,
spin them by hand and listen for noise at the hubs.
Replace any faulty wheel bearings.
Knock At Low Speeds
Low speed knock can be caused by worn universal joints
or a side gear hub counter bore in the cage that is worn
oversize. Inspect and replace universal joints or cage and
side gears as required.
Backlash Clunk
Excessive clunk on acceleration and deceleration can be
caused by a worn rear axle pinion shaft, a worn cage,
excessive clearance between the axle and the side gear
splines, excessive clearance between the side gear hub
and the counterbore in the cage, worn pinion and side
gear teeth, worn thrust washers, or excessive drive pinion
and ring gear backlash. Remove worn parts and replace
as required. Select close–fitting parts when possible.
Adjust pinion and ring gear backlash.

DIFFERENTIAL (REAR 244mm)
4A2B–3
Diagnosis
Many noises that seem to come from the rear axle
actually originate from other sources such as tires, road
surface, wheel bearings, engine, transmission, muffler, or
body drumming. Investigate to find the source of the
noise before disassembling the rear axle. Rear axles, like
any other mechanical device, are not absolutely quiet but
should be considered quiet unless some abnormal noise
is present.
To make a systematic check for axle noise, observe the
following:
1. Select a level asphalt road to reduce tire noise and
body drumming.
2. Check rear axle lubricant level to assure correct level,
and then drive the vehicle far enough to thoroughly
warm up the rear axle lubricant.
3. Note the speed at which noise occurs. Stop the
vehicle and put the transmission in neutral. Run the
engine speed slowly up and down to determine if the
noise is caused by exhaust, muffler noise, or other
engine conditions.
4. Tire noise changes with different road surfaces; axle
noises do not. Temporarily inflate all tires to 344 kPa
(3.5kg/cm
2, 50 psi) (for test purposes only). This will
change noise caused by tires but will not affect noise
caused by the rear axle.
Rear axle noise usually stops when coasting at
speeds under 48 km/h (30 mph); however, tire noise
continues with a lower tone. Rear axle noise usually
changes when comparing pull and coast, but tire
noise stays about the same.
Distinguish between tire noise and rear axle noise by
noting if the noise changes with various speeds or
sudden acceleration and deceleration. Exhaust and
axle noise vary under these conditions, while tire
noise remains constant and is more pronounced at
speeds of 32 to 48 km/h (20 to 30 mph). Further check
for tire noise by driving the vehicle over smooth
pavements or dirt roads (not gravel) with the tires at
normal pressure. If the noise is caused by tires, it will
change noticeably with changes in road surface.
5. Loose or rough front wheel bearings will cause noise
which may be confused with rear axle noise; however,
front wheel bearing noise does not change when
comparing drive and coast. Light application of the
brake while holding vehicle speed steady will often
cause wheel bearing noise to diminish. Front wheel
bearings may be checked for noise by jacking up the
wheels and spinning them or by shaking the wheels to
determine if bearings are loose.
6. Rear suspension rubber bushings and spring
insulators dampen out rear axle noise when correctly
installed. Check to see that there is no link or rod
loosened or metal–to–metal contact.
7. Make sure that there is no metal–to–metal contact
between the floor and the frame.
After the noise has been determined to be in the axle, the
type of axle noise should be determined, in order to make
any necessary repairs.
Gear Noise
Gear noise (whine) is audible from 32 to 89 km/h (20 to 55
mph) under four driving conditions.
1. Driving under acceleration or heavy pull.
2. Driving under load or under constant speed.
3. When using enough throttle to keep the vehicle from
driving the engine while the vehicle slows down
gradually (engine still pulls slightly).
4. When coasting with the vehicle in gear and the throttle
closed. The gear noise is usually more noticeable
between 48 and 64 km/h (30 and 40 mph) and 80 and
89 km/h (50 and 55 mph).
Bearing Noise
Bad bearings generally produce a rough growl or grating
sound, rather than the whine typical of gear noise.
Bearing noise frequently “wow–wows” at bearing rpm,
indicating a bad pinion or rear axle side bearing. This
noise can be confused with rear wheel bearing noise.
Rear Wheel Bearing Noise
Rear wheel bearing noise continues to be heard while
coasting at low speed with transmission in neutral. Noise
may diminish by gentle braking. Jack up the rear wheels,
spin them by hand and listen for noise at the hubs.
Replace any faulty wheel bearings.
Knock At Low Speeds
Low speed knock can be caused by worn universal joints
or a side gear hub counter bore in the cage that is worn
oversize. Inspect and replace universal joints or cage and
side gears as required.
Backlash Clunk
Excessive clunk on acceleration and deceleration can be
caused by a worn rear axle pinion shaft, a worn cage,
excessive clearance between the axle and the side gear
splines, excessive clearance between the side gear hub
and the counterbore in the cage, worn pinion and side
gear teeth, worn thrust washers, or excessive drive pinion
and ring gear backlash. Remove worn parts and replace
as required. Select close–fitting parts when possible.
Adjust pinion and ring gear backlash.

4B1–25 DRIVE LINE CONTROL SYSTEM (SHIFT ON THE FLY)
Diagnosis of the Faults Based on the
Status of 4WD Indicator Lamp, 4WD
Switch and T/F Change Lever
Diagnosis charts are shown on below. If troubles can not
be solved after every chart was traced, troubles may
occur in the 4WD control unit. In this case, replace the
4WD control unit and trace every chart again.
Fault on switching from 2WD to 4WD
1.In case that 4WD indicator’s blinking changes
from 2Hz to 4Hz after Solution 1 is carried out.
Faults occur in the motor actuator or the transfer case
assembly. Remove the motor actuator and check
function. If problem was found and it was repaired, try
Solution 1 again. After that, disassemble the
transfer case assembly for check and repair or
replace. If incident is not improved after above
mentioned actions were taken, replace the 4WD
control unit.
2.In case that 4WD indicator does not blink nor
light, when switching from 2WD to 4WD.
Step
ActionYe sNo
1Is ignition turned on?
Go to Step 2
Turn on the
ignition and trace
this chart from
start.
2
Does the indicator light comes on when the engine is not started?
Go to Step 3
Burning out of
indicator lamp or
disconnection of
harness wire.
Trace this chart
from the start
after repair or
replace.
3Start the engine.
Is the 4WD switch turned from 2WD to 4WD?Short-circuit
(body short) on
harness of the
4WD switch.
Fault of the 4WD
switch (holding
the closed
condition).
Trace this chart
from the start
after repair or
replace.
Push the 4WD
switch to 4WD.

DRIVE LINE CONTROL SYSTEM (TOD) 4B2–24
No.NAMECONTENTS
1VIGPower supply (IG)
2N.CNot used
34WD OUT4WD signal output
4SOL (+)Electromagnetic solenoid
5ADC (+)Axle disconnect output
6LIGHTING SWLighting SW input
7BRAKEBrake SW input
84H SW4H SW input
94L SW4L SW input
10AXEL SWAXEL SW input
11ABS INOperation signal input
12TOD SWTOD SW input
13DIAGSelf-diagnosis input
14D-G MAPD-G MAP recognition input (Only V6 engine)
15Ref.Vehicle speed sensor supply
16N.CNot used
17US/JAPDestination recognition input
18COM (–)Vehicle speed sensor GND
19S-GNDSensor GND
20P-GNDPower GND
21TPSThrottle position sensor
22TECH 2TECH 2 output
23Rer. SigRear vehicle speed sensor input
24Frt. SigFront vehicle speed sensor input
25IND.a4WD disply signal a
26IND.b4WD display signal b
27IND.c4WD display signal c
28IND.AUTOAUTO display output
29IND RrRear display output
30CHECKTOD warning lamp

DRIVE LINE CONTROL SYSTEM (TOD) 4B2–26
Checking Failed TOD Control Unit Pin
NOTE:
1. Unplug the ECU connector and the pins, unless
otherwise specified.2. Before removing the ECU, turn off the ignition switch.
3. If the standard values are not observed, check the
pins with other testers.
Check
Pin
No.Circuit to be
testedIgnition
Switch
PositionEngine
StateMultimeter
Scale/
RangeMeasure
between Pin
NumberStandard ValveNote
14D-G MAPOFFSTOP14, 19Continuity : OK
(Gasoline)
20P-GNDOFFSTOP20, 19Continuity : OK
19GNDOFFSTOP19, GNDContinuity : OK
84H SWOFFSTOP8, 19No continuity (high,
4L) and continuity
(N) : OK
94L SWOFFSTOP9, 19No continuity (high)
and continuity (4L,
N) : OK
10AXLE SWONRUN10, 19Continuity : OKRemove ECU and start the engine. Move
the vehicle forth and back to connect axle
surely.
13DIAGOFFSTOP13 (TOD), 8
(DLC Con-
nector)Continuity : OKDLC connector terminal 8
25IND.aONSTOPDCV25 (+), 19 (–)8.0 14.5 VLighting SW ON : 0V
Lighting SW OFF : 8.0 14.5 V
26IND.bONSTOPDCV26 (+), 19 (–)8.0 14.5 V
27IND.cONSTOPDCV27 (+), 19 (–)8.0 14.5 V
30CHECK
LAMPONSTOPDCV30 (+), 19 (–)8.0 14.5 V
11ABS INONSTOPDCV11 (+), 19 (–)11 . 5 14.5 V
15Ref.ONSTOPDCV15 (+), 19 (–)5 9 VConnect ECU
24Ft.(+)ONSTOPDCV24 (+), 19 (–)0.7 6 VConnect ECU (off one tooth of speed
sensor ring) and move the vehicle making
sure of voltage change.
23Rr.(+)ONSTOPDCV23 (+), 19 (–)0.7 6 VConnect ECU (off one tooth of speed
sensor ring) and move the vehicle making
sure of voltage change.
18COM(-)ONSTOPDCV18 (+), 19 (–)0VConnect ECU
1VigONSTOPDCV1 (+), 19 (–)8 14.5 V
7BRAKEOFFSTOPDCV7 (+), 19 (–)8 14.5 VPress brake pedal
21TPSONSTOPDCV21 (+), 19 (–)0.2 4.6 VStep on the accelerator pedal and make
sure that voltage changes.
34WD OUTOFFSTOP3, 197 12 kDisconnect battery GND terminal
5ADC(+)OFFSTOP5, 1910 30 Disconnect battery GND terminal
4SOL(+)OFFSTOP4, 191.0 5.0 Disconnect battery GND terminal
12TOD SWONSTOPDCV12 (+), 19 (–)SW OFF : 0 V
SW ON : 8.0 14.5 VSW OFF : Contact point open
SW ON : Contact point close
6LIGHTINGONSTOPDCV6 (+), 19 (–)SW OFF : 8.0 14.5
V
SW ON : 0 V
28AUTO INDIONSTOPDCV28 (+), 19 (–)TOD : 0 V
2H & 4L : 8.0 14.5
VLighting SW ON : 0V
Lighting SW OFF : 8.0 14.5 V
29RR INDIONSTOPDCV29 (+), 19 (–)0 V
17US/JAPOFFSTOP17 (+), 19 (–)No continuity : OK

5A–1 BRAKE CONTROL SYSTEM
BRAKES
CONTENTS
Brake Control System 5A. . . . . . . . . . . . . . . . . . . .
Anti–lock Brake System 5B. . . . . . . . . . . . . . . . . . Power–Assisted Brake System 5C. . . . . . . . . . . .
Parking Brakes 5D. . . . . . . . . . . . . . . . . . . . . . . . .
BRAKE CONTROL SYSTEM
CONTENTS
Service Precaution 5A–2. . . . . . . . . . . . . . . . . . . . . .
General Description 5A–3. . . . . . . . . . . . . . . . . . . . .
System Components 5A–3. . . . . . . . . . . . . . . . . . .
Electronic Hydraulic Control Unit (EHCU) 5A–3.
ABS Warning Light 5A–4. . . . . . . . . . . . . . . . . . . .
Wheel Speed Sensor 5A–4. . . . . . . . . . . . . . . . . .
G-Sensor 5A–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Normal and Anti-lock Braking 5A–4. . . . . . . . . . .
Brake Pedal Travel 5A–4. . . . . . . . . . . . . . . . . . . .
Acronyms and Abbreviations 5A–4. . . . . . . . . . . .
General Diagnosis 5A–5. . . . . . . . . . . . . . . . . . . . . . .
General Information 5A–5. . . . . . . . . . . . . . . . . . . .
ABS Service Precautions 5A–5. . . . . . . . . . . . . . .
Computer System Service Precautions 5A–5. . .
General Service Precautions 5A–5. . . . . . . . . . . .
Note on Intermittents 5A–5. . . . . . . . . . . . . . . . . . .
Test Driving ABS Complaint Vehicles 5A–6. . . . .
“ABS” Warning Light 5A–6. . . . . . . . . . . . . . . . . . .
Normal Operation 5A–6. . . . . . . . . . . . . . . . . . . . .
Basic Diagnostic Flow Chart 5A–6. . . . . . . . . . . .
Basic Inspection Procedure 5A–7. . . . . . . . . . . . .
Tech 2 Scan Tool 5A–8. . . . . . . . . . . . . . . . . . . . . .
Getting Started 5A–9. . . . . . . . . . . . . . . . . . . . . . . .
Operating Procedure 5A–10. . . . . . . . . . . . . . . . . . .
Data List 5A–11. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EHCU Connector Pin-out Checks 5A–12. . . . . . . .
Circuit Diagram (LHD model / 6VD1 and
4JG2) 5A–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Diagram (LHD model / 4JG2) 5A–14. . . . .
Circuit Diagram (LHD model / 4JG2) 5A–15. . . . .
Circuit Diagram (LHD model / 6VD1) 5A–16. . . . .
Circuit Diagram (LHD model / 6VD1) 5A–17. . . . .
Connector List (LHD model) 5A–18. . . . . . . . . . . .
Part Location (LHD model) 5A–20. . . . . . . . . . . . . .
Circuit Diagram (RHD model / 6VD1 and
4JG2) 5A–21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Diagram (RHD model / 4JG2) 5A–22. . . . .
Circuit Diagram (RHD model / 4JG2) 5A–23. . . . .
Circuit Diagram (RHD model / 6VD1) 5A–24. . . . .
Circuit Diagram (RHD model / 6VD1) 5A–25. . . . .
Circuit Diagram (RHD model / 6VE1 and
4JX1) 5A–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Circuit Diagram (RHD model / 4JX1) 5A–27. . . . .
Circuit Diagram (RHD model / 4JX1) 5A–28. . . . .
Circuit Diagram (RHD model / 6VE1) 5A–29. . . . .
Circuit Diagram (RHD model / 6VE1) 5A–30. . . . .
Connector List (RHD model) 5A–31. . . . . . . . . . . .
Part Location (RHD model) 5A–34. . . . . . . . . . . . .
Symptom Diagnosis 5A–35. . . . . . . . . . . . . . . . . . . . .
Chart A–1 ABS Works Frequently But
Vehicle Does Not Decelerate 5A–35. . . . . . . . . . .
Chart TA-1 ABS Works Frequently But
Vehicle Does Not Decelerate (Use
TECH 2) 5A–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chart A-2 Uneven Braking Occurs While
ABS Works 5A–36. . . . . . . . . . . . . . . . . . . . . . . . . . .
Chart A-3, TA-3 The Wheels Are Locked 5A–36.
Chart A-4 Brake Pedal Feed Is Abnormal 5A–37.
Chart A-5, TA-5 Braking Sound (From
EHCU) Is Heard While Not Braking 5A–38. . . . . .
Diagnostic Trouble Codes 5A–39. . . . . . . . . . . . . . . .
Diagnosis By “ABS” Warning Light
Illumination Pattern 5A–40. . . . . . . . . . . . . . . . . . . . .
Diagnostic Trouble Codes (DTCs) 5A–40. . . . . . .
Chart B-1 With the key in the ON position
(Before starting the engine). Warning light
(W/L) is not activated. 5A–43. . . . . . . . . . . . . . . . .
Chart B-2 EHCU Abnormality (DTC 14) 5A–43. . .
Chart B-3 Power Voltage Drop (DTC 15) 5A–44. .
Chart B-4 CLASS-2 Communication Line
Abnormality (DTC 16) 5A–44. . . . . . . . . . . . . . . . .
Chart B-5 G-Sensor Circuit (DTC 21) 5A–45. . . . .
Chart B-6 Abnormal Transmission Input
(DTC 23) 5A–46. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chart B-7 Transfer Monitor (DTC 24) 5A–47. . . . .
Chart B-8 EHCU Pump Motor And Motor
Relay Circuit (DTC 32) 5A–47. . . . . . . . . . . . . . . . .
Chart B-9 EHCU Pump Valve And Valve
Relay Circuit (DTC 35) 5A–47. . . . . . . . . . . . . . . . .
Chart B-10 FL Isolation Solenoid Valve
Abnormality (DTC 41) 5A–48. . . . . . . . . . . . . . . . .
Chart B-11 FL Dump Solenoid Valve
Abnormality (DTC 42) 5A–48. . . . . . . . . . . . . . . . .
Chart B-12 FR Isolation Solenoid Valve
Abnormality (DTC 43) 5A–48. . . . . . . . . . . . . . . . .
Chart B-13 FR Dump Solenoid Valve
Abnormality (DTC 44) 5A–49. . . . . . . . . . . . . . . . .
Chart B-14 Rear Isolation Solenoid Valve
Abnormality (DTC 45) 5A–49. . . . . . . . . . . . . . . . .
Chart B-15 Rear Dump Solenoid Valve
Abnormality (DTC 46) 5A–49. . . . . . . . . . . . . . . . .

5A–4
BRAKE CONTROL SYSTEM
normal braking when a malfunction has occurred in the
ABS.
The EHCU has a self-diagnosing function which can
indicate faulty circuits during diagnosis.
The EHCU is mounted on the engine compartment front
right side. It consists of a Motor, Plunger Pump, Solenoid
Valves and Check Valve.
On the outside, the relay box containing a motor relay and
a valve relay is installed.
Solenoid Valves: Reduces or holds the caliper fluid
pressure for each front disc brake or both rear disc brakes
according to the signal sent from the EHCU.
Reservoir: Temporarily holds the brake fluid that returns
from the front and rear disc brake caliper so that pressure
of front disc brake caliper can be reduced smoothly.
Plunger Pump: Feeds the brake fluid held in the reservoir
to the master cylinder.
Motor: Drives the pump according to the signal from
EHCU.
Check Valve: Controls the brake fluid flow.
ABS Warning Light
821RW033Vehicles equipped with the Anti-lock Brake System have
an amber “ABS” warning light in the instrument panel.
The “ABS” warning light will illuminate if a malfunction in
the Anti-lock Brake System is detected by the Electronic
Hydraulic Control Unit (EHCU). In case of an electronic
malfunction, the EHCU will turn “ON” the “ABS” warning
light and disable the Anti-lock braking function.
The “ABS” light will turn “ON” for approximately three
seconds after the ignition switch is to the “ON” position.
If the “ABS” light stays “ON” after the ignition switch is the
“ON” position, or comes “ON” and stays “ON” while
driving, the Anti-lock Brake System should be inspected
for a malfunction according to the diagnosis procedure.
Wheel Speed Sensor
It consists of a sensor and a rotor. The sensor is attached
to the knuckle on the front wheels and to the axle shaft
bearing holder on the rear wheels.
The rotor is press-fit in the axle shaft.The flux generated from electrodes magnetized by a
magnet in the sensor varies due to rotation of the rotor,
and the electromagnetic induction generates alternating
voltage in the coil. This voltage draws a “sine curve” with
the frequency proportional to rotor speed and it allows
detection of wheel speed.
G-Sensor
The G-sensor installed inside the center console detects
the vehicle deceleration speed and sends a signal to the
EHCU. In 4WD operation, all four wheels may be
decelerated in almost the same phase, since all wheels
are connected mechanically.
This tendency is noticeable particularly on roads with low
friction coefficient, and the ABS control is adversely
affected.
The G-sensor judges whether the friction coefficient of
road surface is low or high, and changes the EHCU’s
operating system to ensure ABS control.
Normal and Anti-lock Braking
Under normal driving conditions, the Anti-lock Brake
System functions the same as a standard power assisted
brake system. However, with the detection of wheel
lock-up, a slight bump or kick-back will be felt in the brake
pedal. This pedal “bump” will be followed by a series of
short pedal pulsations which occurs in rapid succession.
The brake pedal pulsation will continue until there is no
longer a need for the anti-lock function or until the vehicle
is stopped. A slight ticking or popping noise may be heard
during brake applications when the Anti-lock features is
being used.
When the Anti-lock feature is being used, the brake pedal
may rise even as the brakes are being applied. This is
also normal. Maintaining a constant force on the pedal
will provide the shortest stopping distance.
Brake Pedal Travel
Vehicles equipped with the Anti-lock Brake System may
be stopped by applying normal force to the brake pedal.
Although there is no need to push the pedal beyond the
point where it stops or holds the vehicle, by applying more
force the pedal will continue to travel toward the floor.
This extra brake pedal travel is normal.
Acronyms and Abbreviations
Several acronyms and abbreviations are commonly used
throughout this section:
ABS
Anti-lock Brake System
CKT
Circuit
DLC
Data Link Connector
EHCU
Electronic Hydraulic Control Unit
FL
Front Left

5A–5 BRAKE CONTROL SYSTEM
FR
Front Right
GEN
Generator
MV
Millivolts
RL
Rear Left
RR
Rear RightRPS
Revolution per Second
VDC
Vo l t s D C
VA C
Vo l t s A C
W/L
Warning Light
WSS
Wheel Speed Sensor
General Diagnosis
General Information
ABS malfunction can be classified into two types, those
which can be detected by the ABS warning light and those
which can be detected as a vehicle abnormality by the
driver.
In either case, locate the fault in accordance with the
“BASIC DIAGNOSTIC FLOWCHART” and repair.
Please refer to Section 5C for the diagnosis of
mechanical troubles such as brake noise, brake judder
(brake pedal or vehicle vibration felt when braking),
uneven braking, and parking brake trouble.
ABS Service Precautions
Required Tools and Items:
Box Wrench
Brake Fluid
Special Tool
Some diagnosis procedures in this section require the
installation of a special tool.
J-39200 High Impedance Multimeter
When circuit measurements are requested, use a circuit
tester with high impedance.
Computer System Service Precautions
The Anti-lock Brake System interfaces directly with the
Electronic Hydraulic Control Unit (EHCU) which is a
control computer that is similar in some regards to the
Powertrain Control Module. These modules are designed
to withstand normal current draws associated with
vehicle operation. However, care must be taken to avoid
overloading any of the EHCU circuits. In testing for opens
or shorts, do not ground or apply voltage to any of the
circuits unless instructed to do so by the appropriate
diagnostic procedure. These circuits should only be
tested with a high impedance multimeter (J-39200) or
special tools 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 switch to the “OFF”
position.
General Service Precautions
The following are general precautions which should be
observed when servicing and diagnosing the Anti-lock
Brake System and/or other vehicle systems. Failure toobserve these precautions may result in Anti-lock Brake
System damage.
If welding work is to be performed on the vehicle using
an electric arc welder, the EHCU and valve block
connectors should be disconnected before the
welding operation begins.
The EHCU and valve block connectors should never
be connected or disconnected with the ignition “ON” .
EHCU of the Anti-lock Brake System are not
separately serviceable and must be replaced as
assemblies. Do not disassemble any component
which is designated as non-serviceable in this
Section.
If only rear wheels are rotated using jacks or drum
tester, the system will diagnose a speed sensor
malfunction and the “ABS” warning light will
illuminate. But actually no trouble exists. After
inspection stop the engine once and re-start it, then
make sure that the “ABS” warning light does not
illuminate.
If the battery has been discharged
The engine may stall if the battery has been completely
discharged and the engine is started via jumper cables.
This is because the Anti-lock Brake System (ABS)
requires a large quantity of electricity. In this case, wait
until the battery is recharged, or set the ABS to a
non-operative state by removing the fuse for the ABS
(40A). After the battery has been recharged, stop the
engine and install the ABS fuse. Start the engine again,
and confirm that the ABS warning light does not light.
Note on Intermittents
As with virtually any electronic system, it is difficult to
identify an intermittent failure. In such a case duplicating
the system malfunction during a test drive or a good
description of vehicle behavior from the customer may be
helpful in locating a “most likely” failed component or
circuit. The symptom diagnosis chart may also be useful
in isolating the failure. Most intermittent problems are
caused by faulty electrical connections or wiring. When
an intermittent failure is encountered, check suspect
circuits for:
Suspected harness damage.
Poor mating of connector halves or terminals not fully
seated in the connector body (backed out).
Improperly formed or damaged terminals.