Isuzu 4HL1 Workshop Manual page 126

1A-124 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 idle up volume switch connector for
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 DTC31 detected?
Check the idle up volume output voltage.
1. Install Tech 2.
2. Starter switch "ON", engine "OFF".
4
3. Observe the "Idle Up Volume" display for
output voltage while operating the idle up
volume switch.
Was the voltage within range?
Check the idle up volume output voltage.
5
Is the voltage 5 V or more?
Check the idle up volume switch circuit for +B
short.
1. Starter switch "OFF".
2. Disconnect the VIM.
6
3. At the VIM connector pins, measure the
resistance.
Was the resistance within range?
Repair or replace the faulty harness.
7
Is the action complete?
at VIM: Inspect
Action
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
8. If pins are jumpered and the resistance reads ∞ Ω,
the cause is open wiring. If pins are not jumpered and
the resistance reads 0 Ω, the cause is short.
Value(s)
—
—
—
approx. 0.4 V
(minimum) ~
4.5 V
(maximum)
—
Pins 34/30/
71-36/38/75/
76: ∞ Ω
—
Yes
Go to Step 2 and go to Step 2
Go to Step 3
Go to Step 4 Diagnostic Aids
Go to Step 12
Go to Step 6
Go to Step 10
Verify repair and
go to Step 12
No
Refer to OBD
System Check
—
Refer to
Go to Step 5
Go to Step 8
Go to Step 7
—