Isuzu 4HL1 Workshop Manual page 111

Step
Check the ground circuit common to ECT and
FT sensors for open wiring or short.
1. Starter switch "OFF".
2. Disconnect the ECM.
3. Disconnect the ETC sensor connector.
7
4. Jumper the ETC sensor connector pins
and measure the resistance at the ECM
connector.
Was the resistance within range?
Repair or replace the faulty harness.
8
Is the action complete?
Review the DTC.
1. Certainly connect the ECT sensor and
ECM connectors.
9
2. Using Tech 2, clear the DTC.
3. Perform test run and review the DTC.
Is DTC23 detected?
Check the ECT sensor output voltage.
1. Using Tech 2, displays the engine data.
2. Starter switch "ON", engine "OFF".
10
3. Observe the "ECT Sensor" display for
output voltage.
Was the voltage within range?
Check the ECT sensor output voltage.
11
Is the voltage fixed to 5 V?
Check the ECT sensor circuit for +B short.
1. Starter switch "OFF".
2. Disconnect the ECM.
12
3. At the ECM connector pins, measure the
resistance.
Was the resistance within range?
Repair or replace the faulty harness.
13
Is the action complete?
Check the ECT sensor circuit harness for
open wiring or short.
1. Starter switch "OFF".
2. Disconnect the ECM.
3. Disconnect the ECT sensor connector.
4. At the ECM connector, measure the
14
resistance.
Was the resistance within range?
Action
Engine Control System 1A-109
Value(s)
Pins 49-46
(not jumpered):
∞ Ω
Pins 46-
ground
(jumpered:
pins 2-
ground): 0 Ω
(not jumpered):
∞ Ω
Go to Step 9
Verify repair and
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go to Step 9
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Go to Step 10
Approx. 0.6 V
(ECT: 80°C)
Go to Step 18
—
Go to Step 12
Pins 49/46-
109/114/115/
116: ∞ Ω
Go to Step 16
Verify repair and
—
go to Step 18
Pins 49-
ground
(jumpered:
pins 1-
ground): 0 Ω
(not jumpered):
∞ Ω
Pins 46-
ground
(jumpered:
pins 2-
ground): 0 Ω
(not jumpered):
∞ Ω
Go to Step 16
Yes No
Go to Step 8
Refer to
Diagnostic Aids
Go to Step 11
Go to Step 14
Go to Step 13
Go to Step 15
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