Isuzu 4HL1 Workshop Manual page 137

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
connectors and wiring harnesses related to the
sensor. A change in the display will indicate the
location of the fault.
Step
Perform the "On-Board Diagnostic (OBD)
System Check".
1
Was the OBD System Check performed?
Check the intake throttle connector for
installation
2
connect it certainly.
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 DTC43 detected?
Check multiple DTCs are set.
Are DTC44 (EGR Position Sensor Fault)or
4
DTC245 (Common Rail Pressure Sensor
Fault) detected together with DTC43?
Check the circuit ground common to ITP
sensor , EGR position sensor and common
rail pressure sensor for +B short.
1. Starter switch "OFF".
5
2. Disconnect the ECM.
3. At the ECM connector pins, measure the
resistance.
Was the resistance within range?
Repair or replace the faulty harness.
6
Is the action complete?
at ECM: Inspect
Action
and, if mounted improperly,
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 DTC44 or DTC245 are also set, the possible
cause is ground circuit common to ITP sensor and
EGR position sensor or common rail pressure sensor.
10. 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.
14. 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)
—
—
—
—
Pins 64 -109/
114/115/116:
∞ Ω
—
Engine Control System 1A-135
Yes
Go to Step 2 and go to Step 2
Go to Step 3
Go to Step 4 Diagnostic Aids
Go to Step 5
Go to Step 7
Verify repair and
go to Step 9
No
Refer to OBD
System Check
—
Refer to
Go to Step 10
Go to Step 6
—