Isuzu N-Series. Manual - part 238

ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-17

ABS Relay

Test condition: Engine stops with the key turned to the
“ON” position. To be more specific, the test is conducted
with the brake pedal stepped on after stepping once and
releasing.
Make sure of the working sound of the ABS relay.
The circuit is normal if the working sound of the ABS re-
lay is made in accordance with Tech 2’s instruction.

ABS Motor

Test condition: Engine stops with the key turned to the
“ON” position. To be more specific, the test is conducted
with the brake pedal stepped on after stepping once and
releasing.
Make sure of the working sound of the ABS motor.
The circuit is normal if the working sound of the ABS mo-
tor is made in accordance with Tech 2’s instruction.

Exhaust Brake Cut Relay

Test condition: Engine stops with the key turned to the
“ON” position. To be more specific, the test is conducted
with the brake pedal stepped on after stepping once and
releasing.
Make sure of the working sound of the exhaust brake cut
relay.
The circuit is normal if the working sound of the exhaust
brake cut relay is made in accordance with Tech 2’s in-
struction.

Hold Valve Test

Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire wrong connections and
valve trouble.
This test will help you confirm the result of your repair
service including the removal/reinstallation of brake
pipe, valve line harness and valve.

Actuator Test

 
F1:
F2:
F3:

 
Return Pump Relay Test
Front Left Solenoid Valve Test
Front Right Solenoid Valve Test

F4:
F5:
F6:
F7:

Rear Left Solenoid Valve Test
Rear Right Solenoid Valve Test
ABS Check Light Test
Exhaust Brake Cut Test

N5A1020E

Actuator Test

F0:

F2:
F3:

ABS Relay Test

Front Left Solenoid Valve Test
Front Right Solenoid Valve Test
Rear Left Solenoid Valve Test
Rear Right Solenoid Valve Test
ABS Check Light Test
Exhaust Brake Cut Test

F4:
F5:
F6:
F7:

N5A1021E

Actuator Test

F0:
F1:
F2:
F3:

ABS Relay Test
Return Pump Relay Test
Front Left Solenoid Valve Test
Front Right Solenoid Valve Test
Rear Left Solenoid Valve Test
Rear Right Solenoid Valve Test
ABS Check Light Test

F4:
F5:
F6:

N5A1022E

Actuator Test

F0:
F1:

F3:

ABS Relay Test
Return Pump Relay Test

Front Right Solenoid Valve Test
Rear Left Solenoid Valve Test
Rear Right Solenoid Valve Test
ABS Check Light Test
Exhaust Brake Cut Test

F4:
F5:
F6:
F7:

N5A1023E

5A4-18 ANTI-LOCK BRAKE SYSTEM (ABS)

Test conditions: The ignition key is the “ON” position
with the four wheels lifted up. The brake pedal is
stepped on, released and stepped on again with the
parking brake released.
Test procedure:

1. Connect Tech 2 with the vehicle, and select Spe-

cial Function from the menus.

2. Select a Hold Valve Menu from the Special Func-

tion Menus.

Select a ISO Solenoid from the Front Left Solenoid
Valve Test Function Menus.

3. Press the Hold Valve “ON” Soft Key with the brake

pedal stepped on.

4. Release the brake pedal.
5. Make sure that the Hold Valve “ON” aimed at by

Tech 2 and the wheel locked position are the
same. If different, check brake pipe, valve line har-
ness wiring and H/UNIT. Repair is needed if abnor-
mality is found.

6. Conduct Step 2 through Step 5 above on all the

four wheels.

Caution:
When conducting this test, please observe the following
cautions.

1. Do not start the engine without fail.
2. Lift up the vehicle at the level floor.

• Secure a clearance from the floor surface

enough to allow the lifted tire to rotate.

3. Maintain the lift up.
4. Wipe the floor surface to remove water and oil so

that the surface may become unslippery.

5. Do not load the vehicle.

• When lifting up the vehicle, be sure to observe

the lifting up points. Refer to vehicle lifting
points in Section 0A GENERAL INFORMA-
TION.

Release Valve Test

Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire wrong connections and
valve trouble.
This test will help you confirm the result of your repair
service including the removal/reinstallation of brake
pipe, valve line harness and valve.

Test conditions: The ignition key is in the “ON” position
with the four wheels lifted up. The brake pedal is
stepped on, released and stepped on again with the
parking brake released.
Test procedure:

1. Connect Tech 2 with the vehicle, and select Spe-

cial Function from the menus.

2. Select a Release Valve Menu from the Special

Function Menus.

Actuator Test

F0:
F1:

F3:

ABS Relay Test
Return Pump Relay Test

Front Right Solenoid Valve Test
Rear Left Solenoid Valve Test
Rear Right Solenoid Valve Test
ABS Check Light Test
Exhaust Brake Cut Test

F4:
F5:
F6:
F7:

N5A1023E

Front Left Solenoid Valve Test

             Dump Solenoid

N5A1024E

Actuator Test

F0:
F1:

F3:

ABS Relay Test
Return Pump Relay Test

Front Right Solenoid Valve Test
Rear Left Solenoid Valve Test
Rear Right Solenoid Valve Test
ABS Check Light Test
Exhaust Brake Cut Test

F4:
F5:
F6:
F7:

N5A1023E

ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-19

Select a Dump Solenoid from the Front Left Solenoid
Valve Test Function Menus.

3. Press the Release Valve “ON” Soft Key with the

brake pedal stepped on.

4. Make sure that the Release Valve “ON” aimed at

by Tech 2 and the wheel released position are the
same. If different, check brake pipe, valve line har-
ness wiring and H/UNIT. Repair is needed if abnor-
mality is found.

5. Conduct Step 2 through Step 4 above on all the

four wheels.

Caution:
When conducting this test, please observe the following
cautions.

1. Do not start the engine without fail.
2. Lift up the vehicle at the level floor.

• Secure a clearance from the floor surface

enough to allow the lifted tire to rotate.

3. Maintain the lift up.

4. Wipe the floor surface to remove water and oil so

that the surface may become unslippery.

5. Do not load the vehicle.

• When lifting up the vehicle, be sure to observe

the lifting up points. Refer to vehicle lifting
points in Section 0A GENERAL INFORMA-
TION.

Actuator Test

F0:
F1:

F3:

ABS Relay Test
Return Pump Relay Test

Front Right Solenoid Valve Test
Rear Left Solenoid Valve Test
Rear Right Solenoid Valve Test
ABS Check Light Test
Exhaust Brake Cut Test

F4:
F5:
F6:
F7:

N5A1023E

Front Left Solenoid Valve Test

             Iso Solenoid

N5A1027E

5A4-20 ANTI-LOCK BRAKE SYSTEM (ABS)

EHCU Connector Pin-out Checks

• Disconnect EHCU.
• Perform checks with high impedance digital multimeter 5-8840-0285-0 (J-39200) or equivalent.

No.

Circuit to be Tested

Key 

Switch 

Position

Multimeter 

Scale/Range

Measure 

between Pin

Nominal Value (24 V 

Battery Vehicle)

Note

1

EHCU Power Circuit

OFF

VDC

3(+) — 1(

−)

0 — 0.3 V

ON

VDC

3(+) — 1(

−)

9.5 — 16.5 V

(16.5 — 34 V)

OFF

VDC

2(+) — 1(

−)

 9.5 — 16.5 V

(16.5 — 34 V)

OFF

VDC

24(+) — 1(

−)

9.5 — 16.5 V

(16.5 — 34 V)

2

EHCU Ground Circuit

OFF

Ω

1(+) — GND

Less than 0.01 

Ω

OFF

Ω

23(+) — GND

Less than 0.01 

Ω

3

EXHIN Circuit

ON

VDC

7(+) — 1(

−)

9.5 — 16.5 V

(16.5 — 34 V)

Engine Run

4

EXHOUT  Circuit

ON

VDC

8(+) — 1(

−)

9.5 — 16.5 V

(16.5 — 34 V)

OFF

VDC

8(+) — 1(

−)

0 — 0.3 V

5

Brake Switch Signal
Circuit

OFF

VDC

16(+) — 1(

−)

0 — 0.3 V

OFF

VDC

16(+) — 1(

−)

9.5 — 16.5 V

(16.5 — 34 V)

Apply Brake
Pedal

6

ABS W/L Circuit

ON

VDC

6(+) — 1(

−)

9.5 — 16.5V

(16.5 — 34 V)

OFF

VDC

6(+) — 1(

−)

0 — 0.3 V

7

FL Speed Sensor

OFF

k

Ω

10(+) — 11(

−)

1 — 2 k

Ω

OFF

k

Ω

10(+) — 1(

−)

More than 1000 k

Ω

OFF

VDC

10(+) — 11(

−)

More than 200 mV

Turn Wheel at
0.5 RPS

8

FR Speed Sensor

OFF

k

Ω

32(+) — 33(

−)

1 — 2 k

Ω

OFF

k

Ω

32(+) — 1(

−)

More than 1000 k

Ω

OFF

VDC

32(+) — 33(

−)

More than 200 mV

Turn Wheel at
0.5 RPS