Isuzu 2008MY N Series Workshop Manual page 63

1A-60 Engine Control System (4HK1)
Step
1. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect for an intermittent, for a poor
connection and corrosion at the harness
connector of the ECM (pin 38 of J-14).
4. Test the Keyword serial data circuits between
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the ECM (pin 38 of J-14) and the DLC (pin 7 of
B-31) for an open circuit or high resistance.
5. Repair the connection(s) or circuit(s) as
necessary.
Did you find and correct the condition?
Notice: An open in a ground circuit at the ECM will
not cause a loss of communication.
1. Check ECM
7
tightness.
2. Clean or tighten grounds as necessary.
Did you find and correct the condition?
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
10
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?
Action
ground for corrosion
Value(s)
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and
—
—
—
—
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Yes
Go to Step 15 Go to Step 7
Go to Step 15 Go to Step 8
Go to Step 13 Go to Step 9
Go to Step 15 Go to Step 13
Go to Step 12 Go to Step 11
Go to Step 15
No
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