Isuzu 4JA1 Workshop Manual page 434

6E-180 Engine Control System (4JH1)
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.
Step
1 Did you perform the 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?
3 1. Test the 5 volts reference circuit between 1the
engine control module (ECM) (pin 55 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?
4 Important: Replacement
programmed.
Replace the ECM. Refer to Engine Control Module
(ECM) Replacement in this section.
Did you complete the replacement?
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?
Action
ECM must
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
Value(s)
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be
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Yes
Go to Diagnostic
System Check-
Go to Step 2 Engine Controls
Go to Diagnostic
Go to Step 3
Go to Step 5 Go to Step 4
Go to Step 5
Go to Step 3 Go to Step 6
No
Aids
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