Isuzu 4HL1 Workshop Manual page 96

1A-94 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.
• 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 CMP sensor and sensor connector
for installation and, if mounted improperly,
2
install these devices 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 DTC14 detected?
Check the CMP sensor ground 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 CMP sensor circuit for open wiring
or short.
1. Starter switch "OFF".
2. Disconnect the ECM.
6
3. At the ECM connector pins, measure the
resistance.
Was the resistance within range?
at ECM: Inspect
Action
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 resistance is sound, the harness and sensor
are not faulty.
7. If pins are jumpered and the resistance reads ∞ Ω,
the cause is open wiring. If pins are not jumpered and
the resistance reads 0Ω, the cause is short.
Value(s)
—
—
—
Pins 27-109/
114/115/116:
∞Ω
—
Pins 8-27:
1850~2450 Ω
Pins 8/27-26:
∞Ω
Pins 8/27-
ground: ∞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 11
Go to Step 11
No
Refer to OBD
System Check
—
Refer to
Go to Step 8
—
Go to Step 7