Isuzu KB P190. Manual — part 306
6E-190 Engine Control System (4JH1)
DTC P1120 (Symptom Code 1) (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 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 4.5 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.
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 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. Observe the Accelerator Pedal Position (APP)
parameter with the scan tool.
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 E-22
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
5
1. Turn OFF the ignition.
2. Connect a DMM between the 5 volts reference
circuit of the APP sensor harness (pin 3 of E-22
connector) and a known good ground.
3. Turn ON the ignition, with the engine OFF.
Is the DMM voltage more than the specified value?
4.5 volts
Go to Step 6
Go to Step 9
Engine Control System (4JH1) 6E-191
Step Action
Value(s)
Yes
No
6
Is the DMM voltage less than the specified value at
step 5?
5.5 volts
Go to Step 7
Go to Step 10
7
Important: The APP sensor may be damaged if the
sensor signal circuit is shorted to a voltage source.
1. Test the signal circuit between the engine control
module (ECM) (pin 38 of C-56 connector) and
the APP sensor (pin 2 of E-22 connector) for the
following conditions:
• A short to battery or ignition voltage
• A short to any 5 volts reference
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
Go to Step 15
Go to Step 14
8
. Test the low reference circuit between the 1ECM
(pin 49 of C-56 connector) and the APP sensor
(pin 1 of E-22 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 15
Go to Step 12
9
1. Test the 5 volts reference circuit between the
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 15
Go to Step 14
10
1. Test the 5 volts reference circuit between the
ECM (pin 57 of C-56 connector) and the APP
sensor (pin 3 of E-22 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 15
Go to Step 14
11
1. Turn OFF the ignition.
2. Inspect for an intermittent and for a poor
connection at the harness connector of the APP
sensor (pin 1 of E-22 connector).
3. Repair the connection(s) as necessary.
Did you find and correct the condition?
Go to Step 15
Go to Step 13
12
1. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect for an intermittent and for a poor
connection on the APP sensor circuit at the
harness connector of the ECM (pin 49 of C-56
connector).
4. Repair the connection(s) as necessary.
Did you find and correct the condition?
Go to Step 15
Go to Step 14
13
Replace APP sensor. Refer to Accelerator Pedal
Position (APP) Sensor Replacement in this section.
Did you complete the replacement?
Go to Step 15
14
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 15
6E-192 Engine Control System (4JH1)
Step Action
Value(s)
Yes
No
15
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 16
16
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-193
DTC P1120 (Symptom Code 7) (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 more than 5.2 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.
DTC P1120 (Symptom Code 7) (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. Test the 5 volts reference circuit between 1the
engine control module (ECM) (pin 57 of C-56
connector) and the accelerator pedal position
(APP) sensor (pin 3 of E-22 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 5
Go to Step 4
4
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 5
5
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 6
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