Isuzu N-Series. Service manual — part 245

Go to Step 5

1. Turn the key off.
2. Disconnect the EHCU connector.
3. Start the engine.
4. Measure voltage between J-177 connec-

tor terminal 2 and J-177 connector termi-
nal 1, 23.
Is the voltage within the specified value?

5. Measure voltage between J-177 connec-

tor terminal 24 and J-177 connector termi-
nal 1, 23.

12 V vehicle:

10 — 16 V

24 V vehicle:

17 — 33.5 V

Go to Step 6

Locate the malfunction of connection in the cir-
cuit.

Is the circuit malfunction specified?

—

Go to Step 4

Repair the malfunction and perform diagnosis
procedure.

Does the DTC repeat?

—

Charge or replace the battery.

Is this step completed?

—

—

Repair open/short circuit or malfunction at con-
nection of connector between J-177 connector
terminal 2 or 24 and fusible link FL- 9.

Is this step completed?

—

—

Replace the EHCU.

Is this step completed?

—

—

1. Install all parts. Verify each part is proper-

ly installed.

2. Clear DTC.

Is this step completed?

—

Go to “Basic diag-

nostic flow chart”.

—

5A4-46 ANTI-LOCK BRAKE SYSTEM (ABS)

Chart 4 (DTC25/C0225) Exhaust Brake Cut Circuit Abnormality

Chart 5 (DTC33/C0233) Motor Drive Circuit Abnormality

Chart 6 (DTC 34/C0234) Abnormal Motor Rotation

• Replace EHCU.

Step

Action

Value(s)

YES

1. Disconnect EHCU connector.
2. Start the engine.
3. Measure voltage between EHCU termi-

nals 8 and 1.

Is the voltage within the specified value?

12 V vehicle:

More than 5 V

24 V vehicle:

More than 10 V

Go to Step 4

Measure voltage between EHCU terminals 7
and 1.

Is the voltage within the specified value?

12 V vehicle:

More than 5 V

24 V vehicle:

More than 10 V

Go to Step 6

Short EHCU terminal 8 to 1.

Is the voltage at EHCU terminal 7 less than 1.5
V?

—

Replace the

EHCU.

Replace the

exhaust brake

cut relay.

Measure resistance of the exhaust brake cut
relay coil.

12 V vehicle:

60 — 120 ohms

24 V vehicle:

210 — 310

ohms

Go to Step 5

Replace the

exhaust brake

cut relay.

Measure voltage at coil power side of relay
box connector. (key at on position)

Is the voltage within the specified value?

12 V vehicle:

10 — 16 V

24 V vehicle:

20 — 32 V

Check harness

between EHCU

terminal 8 and
exhaust brake

cut relay.

Repair as neces-

sary.

Repair harness

and/or power

line.

Turn the exhaust brake switch on.

Does the exhaust brake indicator light turn on?

—

Repair harness

of EHCU terminal

Go to exhaust

brake diagnosis

procedure.

Step

Action

Value(s)

YES

1. Disconnect EHCU connector.
2. Measure voltage between EHCU termi-

nals 24 and 23.

Is the voltage within the specified value?

12 V vehicle:

10 — 16 V

24 V vehicle:

20 — 32 V

Measure continuity between EHCU terminals
23 and 1.

Is there continuity?

—

Replace the

EHCU.

Repair the har-

ness.

Check the ABS fusible link (12 V: 60 A, 24 V:
40 A).

Is it okay?

—

Repair the har-

ness.

Replace the ABS

fusible link

(12 V: 60 A, 24 V:

40 A)

ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-47

Chart 7 (DTC41/C0241) Solenoid Valve Power Supply Abnormality

Chart 8 (DTC 43, 45/C0243, C0245) Solenoid Valve Circuit Abnormality

• Replace EHCU.

Chart 9 (DTC51/C0251) FL Speed Sensor Circuit Abnormality

Chart 10 (DTC52/C0252) FR Speed Sensor Circuit Abnormality

Step

Action

Value(s)

YES

1. Disconnect EHCU connector.
2. Measure voltage between EHCU termi-

nals 2 and 1.

Is the voltage within the specified value?

12 V vehicle:

10 — 16 V

24 V vehicle:

20 — 32 V

Replace the

EHCU.

Check the ABS fusible link (12 V: 60 A, 24 V:
40 A).

Is it okay?

—

Repair the har-

ness.

Replace the ABS

fusible link

(12 V: 60 A, 24 V:

40 A).

Step

Action

Value(s)

YES

1. Disconnect EHCU connector.
2. Measure resistance between EHCU ter-

minals 32 and 33.

Is the resistance within the specified value?

1 — 2 k ohms

Replace the

EHCU.

1. Disconnect the FL speed sensor connec-

tor.

2. Measure the FL speed sensor resistance.

Is the resistance within the specified value?

1 — 2 k ohms

Repair the har-

ness.

Replace the FL

speed sensor.

Step

Action

Value(s)

YES

1. Disconnect EHCU connector.
2. Measure resistance between EHCU ter-

minals 10 and 11.

Is the resistance within the specified value?

1 — 2 k ohms

Replace the

EHCU.

1. Disconnect the FR speed sensor connec-

tor.

2. Measure the FR speed sensor resistance.

Is the resistance within the specified value?

1 — 2 k ohms

Repair the har-

ness.

Replace the FR

speed sensor.

5A4-48 ANTI-LOCK BRAKE SYSTEM (ABS)

Chart 11 (DTC53/C0253) RL Speed Sensor Circuit Abnormality

Step

Action

Value(s)

YES

1. Turn the key off.
2. Disconnect EHCU connector J-177 and

RL speed sensor connector J-149 (J-78).

3. Check the continuity between connector

J-177 terminal 34 and sensor connector
J-149 (J-78) terminal 2 (1).

Is there continuity?

—

Check the continuity between connector J-177
terminal 34 and connector J-177 terminal 1.

Is there continuity?

—

Check the continuity between connector J-177
terminal 22 and sensor connector J-149 (J-78)
terminal 1 (2).

Is there continuity?

—

Go to Step 4

Check the continuity between connector J-177
terminal 22 and connector J-177 terminal 1.

Is there continuity?

—

Go to Step 5

1. Connect the connector J-177 with EHCU.
2. Turn the key on.
3. Using DVM, measure the voltage be-

tween connector J-149 (J-78) terminal 1
(2) (vehicle side) and ground.

Does the DVM display a voltage within the
specified value?

9 — 16 V

Go to Step 6

Check the RL sensor output. (Refer to Chart
C-1-3)

Does the DTC repeat?

—