Isuzu 4HL1, Workshop Manual

Page: 193 / 267

Engine Control System 1A-191
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 DTC23 is also set, the possible cause is the
ground circuit common to FT and ECT sensors.
7. If pins are jumpered and the resistance read
∞ Ω
, the
cause is open wiring. If pins are not jumpered and the
resistance reads 0
Ω
, the cause is short.
10. 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.
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 FT sensor connector for installation
and, if mounted improperly, install the device
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 DTC211 detected?
—
Go to Step 4
Refer to
Diagnostic Aids
4
Check multiple DTCs are set.
Is DTC23 (ECT Sensor System Fault)
detected together with DTC211?
—
Go to Step 5 Go to Step 10
5
Check the ground circuit common to FT and
ECT sensors for +B short.
1. Starter switch "OFF".
2. Disconnect the ECM.
3. At the ECM connector pins, measure the
resistance.
Was the resistance within range?
Pins 46-109/
114/115/116:
∞ Ω
Go to Step 7 Go to Step 6
6
Repair or replace the faulty harness.
Is the action complete?
—
Verify repair and
go to Step 9 —
7
Check the ground circuit common to FT and
ECT sensors for open wiring or short.
1. Starter switch "OFF".
2. Disconnect the ECM.
3. Disconnect the FT sensor connector.
4. Jumper the FT sensor connector pin and
measure the resistance at the ECM
connector.
Was the resistance within range?
Pins 48-46
(not jumpered):
∞ Ω
Pins 46-
ground
(jumpered:
pins 2-
ground): 0
Ω
(not jumpered):
∞ Ω
Go to Step 9 Go to Step 8