Isuzu 2008MY N Series Workshop Manual page 56

Step
1. Turn OFF the ignition.
2. Reconnect the ECM harness connector if
disconnected.
3. Replace the ECM main relay with the glow
relay or replace with a known good relay.
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4. Turn ON the ignition, with the engine OFF.
5. Attempt to establish communication with the
ECM.
Does the scan tool communicate with the
ECM?
1. Turn OFF the ignition.
2. Remove the ECM main relay.
3. Turn ON the ignition, with the engine OFF.
4. Using a test lamp, check for both voltage
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supply circuit to the ECM main relay (pins 1
and 2 of X-18).
5. Repair the open circuit(s) as necessary.
Did you find and correct the condition?
1. Reinstall the ECM main relay.
2. Turn the ignition ON and OFF while listening
of feeling for the ECM main relay click. Wait 7
13
seconds between transitions.
Does the ECM main relay click when the
ignition switch is turned ON or OFF?
Repair the ECM main relay ground circuit between
the ECM main relay (pin 5 of X-18) and chassis
ground terminal (J-13) for the following conditions:
• An open circuit
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• High resistance or a poor connection at the ECM
main relay or ground terminal
Did you complete the repair?
1. Test the battery voltage circuit between the
ECM (pins 2 and 5 of J-14) and the ECM main
relay for the following conditions:
• An open circuit
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• High resistance or a poor connection at
the ECM or ECM main relay
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
Replace the ECM main relay.
16
Did you complete the replacement?
Important: Replacement
programmed and learned.
17
Replace the ECM. Refer to ECM Replacement.
Did you complete the replacement?
Action
ECM must
Engine Control System (4HK1)
Value(s)
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be
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Yes
Go to Step 16 Go to Step 12
Go to Step 18 Go to Step 13
Go to Step 15 Go to Step 14
Go to Step 18
Go to Step 18 Go to Step 17
Go to Step 18
Go to Step 18
1A-53
No
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