Alternator Control Module (ACM), Faulty Communication

Alternator control module (ACM), faulty communication

Checking the wiring
The diagnostic trouble code (DTC) is stored if there is no communication between the engine control module (ECM) and the alternator control module (ACM). This may be due to a fault in the signal cable between the control modules or a damaged communication device in one or both of the control modules.

Hint: This diagnostic trouble code (DTC) can be stored if a generator (GEN) with a charge regulator not intended for LIN communication is installed.

Check the connector on the alternator control module (ACM). Check for contact resistance and oxidation.
Check the signal cable. Check for an open-circuit. Check for a short-circuit to ground. Check for a short-circuit to supply voltage.
Take readings between:
- Engine control module (ECM) #A88 (#B28) and Alternator control module (ACM) #A2.
Remedy as necessary.

Other information
- Connecting the breakout box Connecting The Breakout Box, Engine Control Module (ECM)
- Signal specification Signal Specification, Engine Control Module (ECM)
- Checking wiring and terminals Checking Wiring And Terminals

Was a fault detected?

Yes - Verification

No - Replacing the control module

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Replacing the control module
Try a new alternator control module (ACM).
Remedy as necessary.

Continue - Verification

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Verification




Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reconnect the connectors, reinstall components etc.
- Start the engine
- Read off the battery voltage and the target value of the generator (GEN) charge voltage
- Load the battery by switching on high current consumers such as high beam and the blower fan etc.
Check that the battery voltage is approximately 13.5-14.9 V. Check that the battery voltage is approximately the same as the target value for the generator (GEN) charge. Try different engine speeds (RPM).





Is the function OK?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information

FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Checking the wiring

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