Isuzu 4HL1 Workshop Manual page 50

1A-48 Engine Control System
13: A Tech 2 parameter that is not within the typical
range may help to isolate the area that is causing the
problem.
Step
Check the main relay.
1. Remove the main relay.
2. Check the main relay for open wiring or
1
short-circuit.
Is the main relay in normal condition?
Replace the main relay
2
Is the action complete?
Observe the CHECK ENGINE lamp for
operation.
1. Starter switch "ON", engine "OFF".
3
2. Observe the CHECK ENGINE lamp.
Is the CHECK ENGINE lamp "ON" for 5
seconds after starter switch "ON"?
Check the data communications are normally
established.
1. Starter switch "OFF".
2. Install Tech 2.
4
3. Starter switch "ON".
4. Using Tech 2, display engine data.
Does Tech 2 display engine data?
Check the data communication circuit for
open wiring or short.
1. Starter switch "OFF", and disconnect the
ECM and VIM.
2. Jumper the data link connector (DLC)
5 pins, and measure resistances at ECM
and VIM connectors.
Was a problem found?
Repair or replace the faulty harness.
6
Is the action complete?
Check the operation of Tech 2 with another
vehicle.
7
Is the Tech 2 in normal condition?
Repair or replace Tech 2.
8
Is the action complete?
Action Value(s)
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Go to Step 3
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Go to Step 3
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Go to Step 4
—
Go to Step 10
ECM pins
88-87
(jumpered:
pins 4-7): 0Ω
(not jumpered):
∞Ω
VIM pins
24-73
(jumpered:
pins 4-7): 0Ω
(not jumpered):
∞Ω
Go to Step 6
Verify repair and
—
go to Step 8
—
Go to Step 9
—
Go to Step 4
Yes No
Go to Step 2
Refer to "Inactive
CHECK ENGINE
Lamp (MIL)
Check" and go to
Step 4
Go to Step 5
Go to Step 7
Go to Step 8
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