Isuzu 4HL1, Workshop Manual

Page: 123 / 267

Engine Control System 1A-121
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 at VIM: Inspect harness
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
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).
Step Action Value(s) Yes No
1
Perform the "On-Board Diagnostic (OBD)
System Check".
Was the OBD System Check performed?
—
Go to Step 2
Refer to OBD
System Check
and go to Step 2
2
Check the PTO accelerator sensor system for
mechanical fault.
1. Check the PTO accelerator sensor
connector for installation and, if mounted
improperly, install the device certainly.
2. Check the matching marks on the PTO
accelerator sensor and bolt for alignment
and, if misaligned, adjust positions of the
sensor and bolt.
Is the action complete?
—
Go to Step 3 —
3
Review the DTC.
1. Using Tech 2, check and store the DTC.
2. Clear the DTC.
3. Perform test run and review the DTC.
Is DTC28 detected?
—
Go to Step 4
Refer to
Diagnostic Aids
4
Check the PTO accelerator sensor output
voltage.
1. Install Tech 2.
2. Starter switch "ON", and display the
engine data.
3. Observe the "PTO Accelerator Sensor"
display for output voltage while operating
the PTO control lever.
Was the voltage within range?
Idling:
0.3-0.6 V
WOT:
4.07-4.67 V
Go to Step 12 Go to Step 5
5
Check the PTO accelerator sensor circuit for
+B short.
1. Starter switch "OFF".
2. Disconnect the VIM.
3. At the VIM connector pins, measure the
resistance.
Was the resistance within range?
Pins 31/34/
71-38/75/76:
∞ Ω
Go to Step 7 Go to Step 6
6
Repair or replace the faulty harness.
Is the action complete?
—
Verify repair and
go to Step 11 —