Lost Communication With The Engine Control Module (Ecm) - Isuzu N 2008 Series Workshop Manual

1A-54 Engine Control System (4JJ1)
Lost Communication with The Engine
Control Module (ECM) (Except Euro 4
Specification)
Circuit Description
The ECM, the transmission control module (TCM), the
hill start aid (HSA) control unit, the supplemental
restraint system (SRS) control unit and the immobilizer
control unit (ICU) communicates with the scan tool over
the Keyword serial data link. However, the ECM, the
electric hydraulic control unit (EHCU), the TCM, the
data recording module (DRM) and the instrument panel
(IP) cluster communicate with each other over the
controller area network (CAN) link. The CAN link is not
used for communication with the scan tool and is
shared only among each module.
Circuit/ System Testing Lost Communication with The Engine Control Module (ECM) (Except Euro 4
Specification)
Step
Did you perform the Diagnostic System Check -
1 Engine Controls?
Attempt to establish communication with the ECM.
2
Does the scan tool communicate with the ECM?
1. Inspect
connections and for corrosion at the ECM E12
and J14 connectors.
3
2. Repair the connection(s) as necessary.
Did you find and correct the condition?
1. Check the ECM (30A) slow blow fuse and
ECM Main (10A) fuse in the chassis fuse
block, ECM (10A) fuse in the cabin fuse block.
Replace and retest if open. If any fuse
continues to open, repair the short to ground
on each circuit fed by that fuse.
2. Turn OFF the ignition.
4
3. Disconnect the ECM J14 harness connector.
4. Turn ON the ignition, with the engine OFF.
5. Connect a test lamp to ground and check for
voltage at ignition voltage supply circuit at the
ECM (pin 24 of J14).
Does the test lamp illuminate?
Repair the open in the ignition voltage circuit to the
ECM.
5
Did you complete the repair?
Action
for an intermittent,
Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views
Value(s)
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for poor
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Yes
Go to Diagnostic
System Check -
Go to Step 2 Engine Controls
Go to Intermittent
Conditions
Go to Step 15
Go to Step 6
Go to Step 15
No
Go to Step 3
Go to Step 4
Go to Step 5
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