Isuzu 4ja1, Workshop Manual

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6E-184 Engine Control System (4JH1)
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