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