Isuzu N-Series. Manual - part 234

 

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Isuzu N-Series. Manual - part 234

 

 

ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-1

BRAKES

SECTION 5A4

ANTI-LOCK BRAKE SYSTEM (ABS)

Contents

GENERAL DESCRIPTION ................................. 5A4-3

Service Precaution .......................................... 5A4-3
General Description......................................... 5A4-3
System Components ....................................... 5A4-4
Electronic Hydraulic Control Unit (EHCU) ....... 5A4-4
Hydraulic Unit (HU).......................................... 5A4-4
ABS Warning Light .......................................... 5A4-4
Wheel Speed Sensor....................................... 5A4-4
Normal and Anti-lock Braking .......................... 5A4-4
Brake Pedal Travel .......................................... 5A4-5
Acronyms and Abbreviations........................... 5A4-5

GENERAL DIAGNOSIS ...................................... 5A4-6

General Information......................................... 5A4-6
ABS Service Precautions ................................ 5A4-6
Computer System Service Precautions........... 5A4-6
General Service Precautions........................... 5A4-6
Note on Intermittents ....................................... 5A4-6
Test Driving ABS Complaint Vehicles ............. 5A4-6
“ABS” Warning Light........................................ 5A4-7
Normal Operation ............................................ 5A4-7
Basic Diagnostic Flow Chart............................ 5A4-7
Basic Inspection Procedure............................. 5A4-8
Tech 2 Scan Tool ............................................ 5A4-9
Tech 2 Features ............................................5A4-10
Getting Started .............................................. 5A4-10
Operating Procedure (For Example) .............5A4-11
DTC Modes ...................................................5A4-12
DTC Information Mode ..................................5A4-12
Plotting Snapshot Graph ...............................5A4-13
Plotting Graph Flow Chart (Plotting Graph after Ob-
taining Vehicle Information) ........................... 5A4-14
Flow Chart for Snapshot Replay (Plotting Graph) . 5A4-15
Tech 2 Data Display ......................................5A4-16
Special Function ............................................5A4-16
EHCU Connector Pin-out Checks .................5A4-20
Parts Location................................................5A4-21
Circuit Diagram.............................................. 5A4-23
Connector List ...............................................5A4-29

SYMPTOM DIAGNOSIS ...................................5A4-34

Symptom Diagnosis....................................... 5A4-34
Chart A-1 ABS Works Frequently But Vehicle Does 
Not Decelerate...............................................5A4-34
Chart TA-1 ABS Works Frequently But Vehicle Does 
Not Decelerate (Use Tech 2).........................5A4-35
Chart A-2 Uneven Braking Occurs While ABS Works....5A4-35
Chart TA-2 Uneven Braking Occurs While ABS Works 
(Use Tech 2)..................................................5A4-36
Chart A-3, TA-3 The Wheels Are Locked ......5A4-36
Chart A-4, TA-4 Braking Sound (from Hydraulic Unit) 
Is Heard While Not Braking ........................... 5A4-37

DIAGNOSTIC TROUBLE CODES .................... 5A4-38

Diagnostic Trouble Codes..............................5A4-38

DIAGNOSIS BY “ABS” WARNING LIGHT ILLUMINA-
TION PATTERN ................................................5A4-39

Diagnosis by “ABS” Warning Light Illumination Pat-
tern.................................................................5A4-39
Diagnostic Trouble Codes (DTCs) .................5A4-40
Chart B-1-1 With the key in the ON position (Before 
starting the engine). Warning light (W/L) is not activat-
ed. ..................................................................5A4-43
Chart 1 (DTC13/C0213) Vehicle Type Error .....5A4-44
Chart 2 (DTC14/C0214) EHCU Abnormality .....5A4-44
Chart 3 (DTC15/C0215) EHCU Voltage Out of Range ...5A4-45
Chart 4 (DTC25/C0225) Exhaust Brake Cut Circuit 
Abnormality ....................................................5A4-46
Chart 5 (DTC33/C0233) Motor Drive Circuit Abnor-
mality..............................................................5A4-46
Chart 6 (DTC 34/C0234) Abnormal Motor Rotation...5A4-46
Chart 7 (DTC41/C0241) Solenoid Valve Power Sup-
ply Abnormality ..............................................5A4-47
Chart 8 (DTC 43, 45/C0243, C0245) Solenoid Valve 
Circuit Abnormality.........................................5A4-47
Chart 9 (DTC51/C0251) FL Speed Sensor Circuit Ab-
normality ........................................................5A4-47
Chart 10 (DTC52/C0252) FR Speed Sensor Circuit 
Abnormality ....................................................5A4-47
Chart 11 (DTC53/C0253) RL Speed Sensor Circuit 
Abnormality ....................................................5A4-48
Chart 12 (DTC54/C0254) RR Speed Sensor Circuit 
Abnormality ....................................................5A4-49
Chart 13 (DTC61/C0261) Abnormal FL Speed Sensor 
Signal .............................................................5A4-50
Chart 14 (DTC62/C0262) Abnormal FR Speed Sen-
sor Signal .......................................................5A4-51
Chart 15 (DTC63/C0263) Abnormal RL Speed Sen-
sor Signal .......................................................5A4-53
Chart 16 (DTC64/C0264) Abnormal RR Speed Sen-
sor Signal .......................................................5A4-54

UNIT INSPECTION PROCEDURE ...................5A4-56

Unit Inspection Procedure..............................5A4-56
Chart C-1-1 FL Speed Sensor Output Inspection Pro-
cedure ............................................................5A4-56
Chart C-1-2 FR Speed Sensor Output Inspection Pro-
cedure ............................................................5A4-57
Chart C-1-3 RL Speed Sensor Output Inspection Pro-
cedure ............................................................5A4-57
Chart C-1-4 RR Speed Sensor Output Inspection Pro-
cedure ............................................................5A4-59
Chart TC-1 Sensor Output Inspection Procedure (Use 
Tech 2)...........................................................5A4-60

ON-VEHICLE SERVICE....................................5A4-61

Electronic Hydraulic Control Unit (EHCU)......5A4-61

ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-3

GENERAL DESCRIPTION

Service Precaution

Caution:
Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number
for that application. ISUZU will call out those fasteners that require a replacement after removal. ISUZU will also call
out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use sup-
plemental coatings (Paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces.
Generally, such coatings adversely affect the fastener torque and the joint clamping force, and may damage the fas-
tener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions
can help you avoid damage to parts and systems.

General Description

The Anti-lock Brake System (ABS) works on all four wheels. A combination of wheel speed sensor and Electronic
Hydraulic Control Unit (EHCU) can determine when a wheel is about to stop turning and adjust brake pressure to
maintain best braking.
This system helps the drive maintain greater control of the vehicle under heavy braking conditions.

Legend

1. Hydraulic Line

7. Load Sensing Proportioning Valve (LSPV)

2. Electronic Line

8. Battery

3. Electronic Hydraulic Control Unit (EHCU)

9. ABS Warning Light

4. Front Wheel Speed Sensor

10. Brake Switch

5. Rear Wheel Speed Sensor
6. Diagnosis Connector

8

ENGINE CONTROLLER

OR

EXH BRAKE CUT RELAY

5

7

4

4

1

3

5

TO EHCU

EHCU

ELECTRONIC HYDRAULIC
CONTROL UNIT(EHCU)

HYDRAULIC UNIT(HU)

2

9
6

ABS
DIAG

TO EHCU

CAB

10

TO EHCU

N5A1001E

5A4-4 ANTI-LOCK BRAKE SYSTEM (ABS)

System Components

The Anti-lock Brake System consists of a Electronic Hy-
draulic Control Unit (EHCU), four Wheel Speed Sensors
and Warning Light.

Electronic Hydraulic Control Unit (EHCU)

The EHCU consists of Electronic Brake Control Module
(EBCM) and Hydraulic Unit (HU).
The EHCU is located at the frame side, in front of rear
spring bracket.
The EHCU consists of ABS control circuits, fault detec-
tor, and a fail-safe. It drives the hydraulic unit according
to the signal from each sensor, cancelling ABS to return
to normal braking when a malfunction has occurred in
the ABS.
The EHCU is self-diagnosing function which can indi-
cate faulty circuits during diagnosis.

Notice:
When disconnecting harness connector from EHCU,
push the tang lock of the connector and release the tang
lock. Then move the lever.

Hydraulic Unit (HU)

It consists of a Motor, Plunger Pump, Solenoid Valves
and Check Valve.
Solenoid Valves: Reduces or holds the caliper fluid
pressure for each front brake or both rear brakes ac-
cording to the signal sent from the EHCU.
Reservoir: Temporarily holds the brake fluid that returns
from the front and rear wheel brake so that pressure of
front wheel brake can be reduced smoothly.
Plunger Pump: Feeds the brake fluid held in the reser-
voir to the master cylinder.
Motor: Drives the pump according to the signal from EH-
CU. Check Valve: Controls the brake fluid flow.

ABS Warning Light

Vehicles equipped with the Anti-lock Brake System has
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 2 seconds after the ig-
nition switch is to the “ON” position, and then will go out.
If the “ABS” light comes “ON” and stays “ON” while driv-
ing, 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 at-
tached to the knuckle on the front wheels and to the
bracket on the brake back plate on the rear wheels.
The front speed sensor is coil type and rear is Hall IC
type.
The sensor rotors press-fitted to front and rear wheel
hubs output pulse frequency depending on wheel rota-
tion.
The speed sensors find vehicle speed from its frequen-
cy.

Normal and Anti-lock Braking

Under normal driving conditions, the Anti-lock Brake
System functions the same as a standard power assist-
ed 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 se-
ries of short pedal pulsations which occurs in rapid suc-
cession. The brake pedal pulsation will continue ANTI-
LOCK BRAKE SYSTEM (ABS) 5A4-7 until there is no
longer a need for the anti-lock function or until the vehi-
cle is stopped. A slight ticking or popping noise may be
heard during brake applications when the Anti-lock fea-
tures is being used.

Push

Push

Push

Tang lock

Lever

Move lever outside

EHCU

CONNECTOR

N5A1002E

N5A1003E

 

 

 

 

 

 

 

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