Isuzu 4HL1 Workshop Manual page 222

1A-220 Engine Control System
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
Step
Perform the "On-Board Diagnostic (OBD)
System Check".
1
Was the OBD System Check performed?
Check the injector connector for installation
and, if mounted improperly, connect it
2
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 DTC271 detected?
Check the cylinder 1 injector drive circuit for
+B short.
1. Starter switch "OFF".
2. Disconnect the ECM.
4
3. At the ECM connector pins, measure the
resistance.
Was the resistance within range?
Repair or replace the faulty harness.
5
Is the action complete?
Check the cylinder 1 injector drive circuit
(ECM to intermediate connector) for open
wiring or short.
1. Disconnect the ECM.
2. Disconnect the injector connector.
6
3. Jumper
measure the resistance at the ECM
connector.
Was the resistance within range?
at ECM: Inspect
Action
the injector connector
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.
harness
3. If the DTC is not detected, the possible cause is
intermittent (intermittent fault).
6. 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 43-109/
114/115/116:
∞ Ω
—
Pins 43-1
(jumpered:
pins 5-1): 0 Ω
(not jumpered):
and
∞ Ω
Yes
Go to Step 2 and go to Step 2
Go to Step 3
Go to Step 4 Diagnostic Aids
Go to Step 6
Verify repair and
go to Step 14
Go to Step 7
No
Refer to OBD
System Check
—
Refer to
Go to Step 5
—
Go to Step 10