Isuzu N-Series. Manual - part 778

 Engine Control System (4JH1)    6E-163

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

6E-164    Engine Control System (4JH1) 

P1110 (Symptom Code 8) (Flash Code 72)

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 intake throttle 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

intake throttle 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 intake throttle solenoid valve control circuit
between the ECM and the solenoid valve is normal,
voltage level low DTC P1110 (Symptom Code 4) will
set.

DTC P1110 (Symptom Code 8) (Flash Code 72)
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 Intake
Throttle 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 intake throttle solenoid valve
harness connector.

3.

Start the engine.

4.

Monitor the DTC Information with the Tech 2.

Does DTC P1110 (Symptom Code 4) set, but not
DTC P1110 (Symptom Code 8)?

—

Go to Step 5

Go to Step 4

4

1.

Test the control circuit between the engine
control module (ECM) (pin 95 of B-233
connector) and the intake throttle solenoid
valve (pin 2 of J-40 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 intake throttle solenoid valve.  Refer to
Intake Throttle Solenoid Valve Replacement in this
section.

Did you complete the replacement?

—

Go to Step 7

—

 Engine Control System (4JH1)    6E-165

6

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 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 Intake
Throttle 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

6E-166    Engine Control System (4JH1) 

P1120 (Symptom Code 1) (Flash Code 21)

Circuit Description
The accelerator pedal position (APP) sensor is
mounted on the accelerator pedal bracket.  The engine
control module (ECM) uses the APP sensors to
determine the amount of acceleration or deceleration
desired by the person driving the vehicle via the fuel
injection control.  The APP sensor has the following
circuits.

• 5 volts reference circuit
• Low reference circuit
• APP sensor signal circuit

The ECM supplies 5 volts to the APP sensor on the 5
volts reference circuit.  The ECM also provides a
ground on the low reference circuit.  The APP sensor
provides a signal to the ECM on the APP sensor signal
circuit, which is relative to the position changes of the
accelerator pedal angle.  The ECM monitors the APP
sensor signal for voltages outside the normal range of
the APP sensor.  If the ECM detects an excessively
high APP sensor signal voltage, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects that the APP sensor signal

voltage is more than 4.9 volts for 0.5 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM uses an engine speed substitution of

1400 RPM.

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.

DTC P1120 (Symptom Code 1) (Flash Code 21)
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.

Start the engine.

4.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic 

Aids

3

1.

Turn OFF the ignition.

2.

Disconnect the accelerator pedal position
(APP) sensor harness connector.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the Accelerator Pedal Position (APP)
parameter with the Tech 2.

Does the APP parameter less than the specified
value?

1%

Go to Step 4

Go to Step 5

4

1.

Turn OFF the ignition.

2.

Connect a test lamp between the low
reference circuit of the APP sensor harness
(pin 1 of B-80 connector) and battery voltage.

3.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 11

Go to Step 8