Fault - Isuzu 4HL1 Workshop Manual

When Tech 2 has been connected to the vehicle, the
DTC can be cleared through the memory clear
operation with Tech 2.
Diagnostic Aids
Poor connection or damaged harness may cause
intermittents. Check for the following conditions and, if
the fault is detected, repair or replace the faulty portion.
• Poor connection
connectors for backed-out pins, improper mating,
broken locks, improperly formed or damaged pins,
and poor pin-to-wire connection.
• Damaged harness: Inspect the wiring harness for
rubbed-through wire insulation or wire broken
inside the insulator. If the harness appears to be
OK, observe the display on Tech 2 while moving
Step
Perform the "On-Board Diagnostic (OBD)
System Check".
1
Was the OBD System Check performed?
Check the AP sensor system for mechanical

fault.

1. Check the AP sensor connector for
installation and, if mounted improperly,
install the device certainly.
2. Check the system components such as
2
accelerator pedal link, bracket, and spring
for fault and, if troubles are found, repair
the faulty portion. (Refer to Section 1B
"Accelerator Pedal".)
Is the action complete?
Review the DTC.
1. Using Tech 2, check and store the DTC.
2. Clear the DTC.
3
3. Perform test run and review the DTC.
Is DTC24 detected?
Check the AP sensor output voltage.
1. Install Tech 2.
2. Starter switch "ON", and display the
engine data.
4
3. Observe the "Accelerator Sensor" display
for output voltage while operating the
accelerator pedal.
Was the voltage within range?
Check the AP sensor output voltage.
5
Is the voltage 5 V or more?
at ECM: Inspect
Action
connectors and wiring harnesses related to the
sensor. A change in the display will indicate the
location of the fault.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
3. If the DTC is not detected, the possible cause is
intermittent (intermittent fault).
harness
4. If the output voltage is fixed to 0 V, the possible
cause is open wiring in the circuit. If the output voltage
is fixed to 5 V, the possible cause is short in the circuit.
8. If pins are jumpered and the resistance reads ∞Ω,
the cause is open wiring. If pins are not jumpered and
the resistance reads 0 Ω, the cause is short.
Value(s)
—
—
—
Idling:
0.43-0.73 V
WOT:
4.2-4.8 V
—
Engine Control System 1A-113
Yes
Go to Step 2 and go to Step 2
Go to Step 3
Go to Step 4 Diagnostic Aids
Go to Step 12
Go to Step 6
No
Refer to OBD
System Check
—
Refer to
Go to Step 5
Go to Step 8