Isuzu 4HL1, Workshop Manual

Page: 249 / 267

Engine Control System 1A-247
6. After the above operations are properly completed,
the CHECK ENGINE lamp (MIL) illuminates for 3
seconds to report the memory is cleared.
7. Turn off the starter switch. Wait for 5 seconds and
turn on the starter switch again.
When Tech 2 has been connected to the vehicle, the
DTC can be cleared through the memory clear
operation with Tech 2.
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.
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 path between starter switch "ST"
and "ON" circuits for short.
1. Starter switch "OFF".
2. Disconnect the ECM.
3. Starter switch "ON".
4. At the ECM connector pins, measure the
resistance.
Was the resistance within range?
Pins 109-113:
∞ Ω
Go to Step 6 Go to Step 3
3
Check the starter switch "ST" circuit harness
for short.
1. Starter switch "OFF".
2. Disconnect the starter switch connector.
3. At the ECM connector pins, measure the
resistance.
Was the resistance within range?
Pins 109-113:
∞ Ω
Go to Step 4 Go to Step 7
4
Check the starter switch.
1. Remove the starter switch.
2. Test the continuity between starter switch
connector pins.
Does the starter switch meet the
requirements?
Pins 3-4
("ON"
position):
Discontinued
("ST"
position):
Continued
Go to Step 6 Go to Step 5
5
Replace the starter switch.
Is the action complete?
—
Verify repair and
go to Step 10 —
6
Check the starter switch "ST" circuit harness
for +B short.
1. Starter switch "OFF".
2. Measure the voltage between ECM
connector pin and ground.
Was the resistance within range?
Pins 113-
ground: 0 V
Go to Step 2 Go to Step 7
7
Repair or replace the faulty harness.
Is the action complete?
—
Verify repair and
go to Step 10 —