Isuzu 4HL1 Workshop Manual page 106

1A-104 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
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 DTC22 detected?
Check the IAT sensor output voltage.
1. Using Tech 2, displays the engine data.
2. Starter switch "ON", engine "OFF".
4
3. Observe the "IAT Sensor" display for
output voltage.
Was the voltage within range?
Check the IAT sensor output voltage.
5
Is the voltage fixed to 5 V?
Check the IAT sensor circuit for open wiring.
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
IAT sensor connector
and, if mounted improperly,
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
5. If the output voltage is fixed to 5 V, the possible
cause is open wiring in the circuit. If the output voltage
is fixed to 0 V, the possible cause is short in the circuit.
Value(s)
—
for
—
—
Approx. 2.8 V
(at 20°C)
—
Pins 91-83:
2.5 kΩ (ECT:
approx. 20°C)
Yes
Go to Step 2 and go to Step 2
Go to Step 3
Go to Step 4
Refer to
Diagnostic Aids
and go to Step 13
Go to Step 6
Go to Step 13
No
Refer to OBD
System Check
—
Refer to
Diagnostic Aids
Go to Step 5
Go to Step 8
Go to Step 7