Isuzu 4HL1, Workshop Manual

Page: 147 / 267

Engine Control System 1A-145
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 ECM: 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).
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.
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 EGR valve connector for
installation and, if mounted improperly,
connect it certainly.
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 DTC45 detected?
—
Go to Step 4
Refer to
Diagnostic Aids
4
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.
Was the resistance within range?
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
Go to Step 6 Go to Step 5
5
Repair or replace the faulty harness.
Is the action complete?
—
Verify repair and
go to Step 9 —
6
Check the EGR DC motor.
1. Measure the resistance between EGR
valve connector pins.
Was the resistance within range?
[Reference]
Pins 4-5:
Approx.
95~105
Ω
Go to Step 8 Go to Step 7