Isuzu 4HL1 Workshop Manual page 238

1A-236 Engine Control System
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.
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 DTC277 detected?
Check the common 1 injector drive circuit
(ECM to intermediate connector) for open
wiring.
1. Disconnect the ECM.
2. Disconnect the injector connector.
3. Jumper
measure the resistance at the ECM
connector.
4
Was the resistance within range?
Check the intermediate connector for fault.
1. Disconnect ECM side and injector side
connectors
connector.
2. Remove the intermediate connector from
the engine block.
3. Jumper the intermediate connector that
5
was connected to the injectors and
measure
intermediate
connected to the ECM pins.
Was the resistance within range?
at ECM: Inspect
Action
the injector connector
from the intermediate
the resistance
connector that
• 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
harness
sensor. A change in the display will indicate the
location of the fault.
Value(s)
—
—
—
Pins 1-
ground
(jumpered:
1/4-ground):
0 Ω
(not jumpered):
and ∞ Ω
Pins 2-
ground
(jumpered:
1/4-ground):
0 Ω
(not jumpered):
∞ Ω
Pins 1-2
(not jumpered):
0 Ω
Pins 1-2/3/4
(jumpered:
1-2/3/4): 0 Ω
(not jumpered):
∞ Ω
Pins 2-3/4
(jumpered:
2-3/4): 0 Ω
(not jumpered):
at the
∞ Ω
was
Pins 3-4
(jumpered:
3-4): 0 Ω
(not jumpered):
∞ Ω
Yes
Refer to OBD
System Check
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 8
Go to Step 7 Go to Step 6
No
—
Refer to