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Home >> Jeep >> 2023 >> Compass Altitude >> Repair and Diagnosis >> Engine Performance >> System >> 2.0L - DTCS U0109 To U0427 >> DTC Troubleshooting >> U012D-Lost Communication With Alternator Control Module >> Diagnostic Test
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Diagnostic Test

  1. READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR THE DTC TO RETURN 
    1. With the scan tool, read DTCs in all Electronic Control Units (ECUs) and record on the repair order.
    2. For future reference, with the scan tool, run and save a vehicle Scan Report and all related recorded data.
    3. With the scan tool, erase all DTCs.
    4. Turn the ignition off for a minimum of 10.0 seconds.
    5. Turn the ignition on.
    6. Using the When Monitored and Set Conditions above and recorded data, operate the vehicle in the conditions that set the DTC.
    7. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      • Go To  2

      No 

  2. CHECK THE (A801) FUSED B+ CIRCUIT VOLTAGE 
    1. Turn the ignition off.
    2. Check the (A801) Fused B+ circuit voltage at the Smart Alternator stud.

      Is battery voltage present?

      Yes 

      • Go To  4

      No 

      • Go To  3
  3. CHECK THE CHARGING SYSTEM FUSE(S) 
    1. Check the charging system fuse(s).

      Are there any open fuses for the charging system?

      Yes 

      • Replace the fuse and repair the (A801) Fused B+ circuit for a short to ground. If the circuit is not shorted to ground, replace the Alternator.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

  4. CHECK THE SMART ALTERNATOR CASE GROUND 
    1. Check for continuity between the Smart Alternator case and a good chassis or battery ground.

      Is there continuity between the Smart Alternator case and a good chassis or battery ground?

      Yes 

      • Go To  5

      No 

      • Repair the poor connection between the Smart Alternator and the engine.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  5. CHECK THE (D511) LIN BUS CIRCUIT FOR A SHORT TO GROUND 
    1. Disconnect the Alternator LIN Bus harness connector.
    2. Disconnect the PCM C2 harness connector.
    3. Check for continuity between ground and the (D511) LIN Bus circuit at the Alternator harness connector.

      Is there continuity between ground and the (D511) LIN Bus circuit?

      Yes 

      • Repair the (D511) LIN Bus circuit for a short to ground.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  6
  6. CHECK THE (D511) LIN BUS CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT 
    CAUTION:

    Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.

    1. Connect the (special tool #10436, Adapter, GPEC Diagnostic) to the PCM C1 harness connector.
    2. Check for continuity between the (D511) LIN Bus circuit and all other circuits at the GPEC Adaptor.

      Is there continuity between the (D511) LIN Bus circuit and any other circuit?

      Yes 

      • Repair the (D511) LIN Bus circuit for a short to the circuit that showed continuity.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  7
  7. CHECK THE (D511) LIN BUS CIRCUIT FOR AN OPEN/HIGH RESISTANCE 
    1. Measure the resistance of the (D511) LIN Bus circuit between the Alternator harness connector and GPEC Adaptor.

      Is the resistance below 2.0 Ohms?

      Yes 

      • Go To  8

      No 

      • Repair the (D511) LIN Bus circuit for a an open or high resistance.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  8. REPLACE THE ALTERNATOR AND RETEST FOR DTCS 
    1. Turn the ignition off.
    2. Replace the component in accordance with the Service Information. Refer to GENERATOR , REMOVAL AND INSTALLATION .
    3. Connect all disconnected harness connectors.
    4. Turn the ignition on.
    5. With the scan tool, erase all DTCs.
    6. Turn the ignition off for a minimum of 10.0 seconds.
    7. Turn the ignition on.
    8. Using the When Monitored and Set Conditions above and recorded data, operate the vehicle in the conditions that set the DTC.
    9. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      • Go To  9

      No 

  9. CHECK RELATED PCM AND COMPONENT CONNECTIONS 
    1. Disconnect all PCM harness connectors.
    2. Disconnect all related in-line harness connections (if equipped).
    3. Disconnect the related component harness connectors.
    4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
      • Proper connector installation.
      • Damaged connector locks.
      • Corrosion.
      • Other signs of water intrusion.
      • Weather seal damage (if equipped).
      • Bent terminals.
      • Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
      • Terminals that have been pushed back into the connector cavity.
      • Check for spread terminals and verify proper terminal tension.

      Repair any conditions that are found.

    5. Connect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    7. Connect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
    8. With the scan tool, erase DTCs.
    9. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
    10. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      No 

      • The wiring or poor connection problem has been repaired.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
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