Isuzu N-Series. Manual - part 786

 Engine Control System (4JH1)    6E-195

5

1.

Connect a 3-amp fused jumper wire across
the exhaust brake solenoid valve harness
connector between pins 1 and 2 of the J-31
connector.

2.

Lift the driving wheels or drive the vehicle.

3.

Let the vehicle run so that the exhaust brake
may operate while observing the Exhaust
Brake Solenoid Command parameter with the
Tech 2.

Does DTC P1576 (Symptom Code 8) set when the
exhaust brake is operating, but not DTC P1576
(Symptom Code 4)?

—

Go to Step 9

Go to Step 7

6

Repair the open circuit or high resistance on the
voltage feed circuit between the ECM main relay
(pin 5 of X-14 connector) and the exhaust brake
solenoid valve (pin 1 of J-31 connector).

Did you complete the repair?

—

Go to Step 13

—

7

1.

Test the control circuit between the engine
control module (ECM) (pin 40 of B-234
connector) and the exhaust brake solenoid
valve (pin 2 of J-31 connector) for an open
circuit or high resistance.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 10

8

1.

Test the control circuit between the ECM (pin
40 of B-234 connector) and the exhaust brake
solenoid valve (pin 2 of J-31 connector) for a
short to ground.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

9

1.

Turn OFF the ignition.

2.

Disconnect the exhaust brake solenoid valve
harness connector.

3.

Inspect for an intermittent and for poor
connections at the harness connector of the
exhaust brake solenoid valve (pins 1 and 2 of
J-31 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 11

10

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection on the exhaust brake solenoid
valve control circuit at the harness connector
of the ECM (pin 40 of B-234 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

11

Replace the exhaust brake solenoid valve.  Refer
to Exhaust Brake Solenoid Valve Replacement in
this section.

Did you complete the replacement?

—

Go to Step 13

—

Step

Action

Value(s)

Yes

No

6E-196    Engine Control System (4JH1) 

12

Important:
Replacement ECM must be programmed.

Replace the ECM.  Refer to Engine Control Module
(ECM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 13

—

13

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine.

5.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 14

14

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic 

Trouble Code (DTC) 

List

System OK

Step

Action

Value(s)

Yes

No

 Engine Control System (4JH1)    6E-197

P1576 (Symptom Code 8) (Flash Code 71)

Circuit Description
The engine control module (ECM) controls the exhaust
brake which energizes the intake throttle solenoid valve
and exhaust brake solenoid valve based on vehicle
running condition.  The ECM commands each solenoid
valve to close each throttle valve by applying vacuum.
If the ECM detects that a short to battery or ignition
voltage on the exhaust brake solenoid valve control
circuit, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects a high voltage condition on the

exhaust brake solenoid valve control circuit for
longer than 3 seconds when the solenoid valve is
commanded ON.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL when the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault.  Or clear with the Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Test Description
The number below refers to the step number on the
diagnostic table.
3. If the exhaust brake solenoid valve control circuit
between the ECM and the solenoid valve is normal,
voltage level low DTC P1576 (Symptom Code 4) will
set.

DTC P1576 (Symptom Code 8) (Flash Code 71)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic 

System Check – 

Engine Controls

2

1.

Install the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Lift the driving wheels or drive the vehicle.

4.

Let the vehicle run so that the exhaust brake
may operate while observing the Exhaust
Brake Solenoid Command with the Tech 2.

Does the Diagnostic Trouble Code (DTC) fail this
ignition when the exhaust brake is operating?

—

Go to Step 3

Go to Diagnostic 

Aids

3

1.

Turn OFF the ignition.

2.

Disconnect the exhaust brake solenoid valve
harness connector.

3.

Start the engine.

4.

Monitor the DTC Information with the Tech 2.

Does DTC P1576 (Symptom Code 4) set, but not
DTC P1576 (Symptom Code 8)?

—

Go to Step 5

Go to Step 4

4

1.

Test the control circuit between the engine
control module (ECM) (pin 40 of B-234
connector) and the exhaust brake solenoid
valve (pin 2 of J-31 connector) for a short to
battery or ignition voltage.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 6

5

Replace the exhaust brake solenoid valve.  Refer
to Exhaust Brake Solenoid Valve Replacement in
this section.

Did you complete the replacement?

—

Go to Step 7

—

6E-198    Engine Control System (4JH1) 

6

Replace the ECM.  Refer to Engine Control Module
(ECM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 7

—

7

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Lift the driving wheels or drive the vehicle.

5.

Let the vehicle run so that the exhaust brake
may operate while observing the Exhaust
Brake Solenoid Command with the Tech 2.

Does the DTC fail this ignition when the exhaust
brake is operating?

—

Go to Step 3

Go to Step 8

8

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic 

Trouble Code (DTC) 

List

System OK

Step

Action

Value(s)

Yes

No