Isuzu KB P190. Manual — part 307

6E-194 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

6

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK

Engine Control System (4JH1) 6E-195

DTC P1120 (Symptom Code 9) (Flash Code 21)

Circuit Description
The accelerator pedal position (APP) sensor is mounted
on the intake throttle assembly. 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 provides 5 volts reference voltage through the
reference circuit to the APP sensor. The ECM monitors
the voltage on the 5 volts reference circuit. If the ECM
detects an excessively high APP sensor 5 volts
reference 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 voltage

supply circuit is less than 4.6 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 scan tool.

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 APP sensor 5 volts reference circuit between
the ECM and the sensor is normal, the sensor signal
correlation DTC P1120 (Symptom Code E) will set.

DTC P1120 (Symptom Code 9) (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 scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Monitor the Diagnostic Trouble Code (DTC)

Information with the scan tool.

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. Depress and release the accelerator pedal many

times.

5. Monitor the DTC Information with the scan tool.
Does DTC P1120 (Symptom Code E) set, but not
DTC P1120 (Symptom Code 9)?



Go to Step 5

Go to Step 4

4

1. Test the 5 volts reference circuit between the

engine control module (ECM) (pin 57 of C-56
connector) and the APP sensor (pin 3 of E-22
connector) for the following conditions:

• A short to ground
• A short to the low reference circuit

2. Repair the circuit(s) as necessary.
Did you find and correct the condition?



Go to Step 7

Go to Step 6

6E-196 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

5

Replace the accelerator pedal position sensor. Refer
to Accelerator Pedal Position Sensor Replacement
in this section.
Did you complete the replacement?



Go to Step 7



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 scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Turn ON the ignition, with the engine OFF.
5. Fully depress and release the accelerator pedal

many times.

6. Monitor the DTC Information with the scan tool.
Did the DTC fail this ignition?



Go to Step 3

Go to Step 8

8

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK

Engine Control System (4JH1) 6E-197

DTC P1120 (Symptom Code D) (Flash Code 21)

Circuit Description
The accelerator pedal position (APP) sensor is mounted
on the intake throttle assembly. 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 brake pedal switch is installed on the brake pedal
bracket. The brake pedal 1 switch is a normally open
type switch and the brake pedal 2 switch is a normally
closed type switch. When the brake pedal is pressed,
the brake pedal 1 switch signal is provided to the ECM
and the stoplights are turned ON. Then, the brake pedal
2 switch signal to the ECM is stopped (low voltage).
If the ECM detects accelerator pedal or APP sensor
signal is stuck while brake pedal is depressed, this DTC
will set.
Condition for Running the DTC

• The ignition switch is ON.
• The engine speed is higher than 1700 RPM.
• The vehicle speed is higher than 1.5 km/h (1

MPH).

Condition for Setting the DTC

• The ECM detects APP sensor angle is stationary

more than 8.7%, then brake pedal is depressed for
longer than 2 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 scan tool.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

• Misadjusted brake pedal switch may set this DTC.
• Misadjusted APP sensor may set this DTC.
• Misadjusted throttle cable may set this DTC.
• A sticking or intermittently sticking the intake

throttle valve, control cable or pedal may set this
DTC.

DTC P1120 (Symptom Code D) (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 scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Monitor the Diagnostic Trouble Code (DTC)

Information with the scan tool.

Was DTC P0703 (Symptom Code A or B) or P1120
(Symptom Code 1, 7, 9 or E) set?



Go to Applicable

DTC

Go to Step 3

3

1. Turn ON the ignition, with the engine OFF.
2. Observe the Brake Pedal 1 Switch parameter

with the scan tool while fully depressing and
releasing the brake pedal.

Does the scan tool indicate Applied when the brake
pedal is applied and Released when the brake pedal
is released?



Go to Step 9

Go to Step 4