Isuzu 4HL1 Workshop Manual page 147

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
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 DTC45 detected?
Check the EGR DC motor drive circuit for
open wiring or short.
1. Starter switch "OFF".
2. Disconnect the ECM.
3. Disconnect EGR valve connector.
4. Jumper the EGR vale connector and
measure the resistance at the ECM
connector.
4
Was the resistance within range?
Repair or replace the faulty harness.
5
Is the action complete?
Check the EGR DC motor.
1. Measure the resistance between EGR
6
valve connector pins.
Was the resistance within range?
at ECM: Inspect
Action
EGR valve connector
and, if mounted improperly,
connectors and wiring harnesses related to the
sensor. A change in the display will indicate the
location of the fault.
Test Description
harness
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).
4. If pins are jumpered and the resistance reads ∞ Ω,
the cause is open wiring. If pins are not jumper and the
resistance reads 0 Ω, the cause is short.
Value(s)
—
for
—
—
Pins 59-58
(jumpered:
pins 4-5): 0 Ω
(not jumpered):
∞ Ω
Pins 59-
ground
(jumpered:
pins 4-
ground): 0 Ω
(not jumpered):
∞ Ω
Pins 58-
ground
(jumpered:
pins 5-
ground): 0 Ω
(not jumpered):
∞ Ω
—
[Reference]
Pins 4-5:
Approx.
95~105 Ω
Engine Control System 1A-145
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 9
Go to Step 8
No
Refer to OBD
System Check
—
Refer to
Go to Step 5
—
Go to Step 7