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Home >> Alfa Romeo >> 2019 >> Giulia Base, AWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 13 (2.9L Pcm 1 - DTCS P3406-00 To U143B-00) >> DTC Troubleshooting >> U0075-00-Control Module Communication Bus C Off >> Diagnostic Test

Diagnostic Test

WARNING: This page is about a different variant/trim than selected.
  1. CHECK FOR AN ACTIVE DTC 
    1. Turn the ignition on.
    2. With the scan tool, read and record DTCs.

      Is the DTC active or pending?

      Yes 

      • Go To  2

      No 

  2. CHECK THE PRIVATE CAN HIGH CIRCUIT FOR A SHORT TO GROUND 
    1. Turn the ignition off.
    2. Disconnect the PCM-1 harness connectors.
    3. Disconnect the PCM-2 harness connectors.
    4. Check for continuity between ground and the Private CAN High Circuit at the PCM-1 harness connector.

      Is there continuity between ground and the Private CAN High Circuit?

      Yes 

      • Repair the Private CAN High Circuit for a short to ground.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  3
  3. CHECK THE PRIVATE CAN LOW CIRCUIT FOR A SHORT TO GROUND 
    1. Check for continuity between ground and the Private CAN Low Circuit at the PCM-1 harness connector.

      Is there continuity between ground and the Private CAN Low Circuit?

      Yes 

      • Repair the Private CAN Low Circuit for a short to ground.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  4
  4. CHECK THE PRIVATE CAN HIGH CIRCUIT FOR AN OPEN/HIGH RESISTANCE 
    1. Measure the resistance of the Private CAN High Circuit between the PCM-1 harness connector and the PCM-2 harness connector.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  5

      No 

      • Repair the Private CAN High Circuit for an open or high resistance.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  5. CHECK THE PRIVATE CAN LOW CIRCUIT FOR AN OPEN/HIGH RESISTANCE 
    1. Measure the resistance of the Private CAN Low Circuit between the PCM-1 harness connector and the PCM-2 harness connector.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  6

      No 

      • Repair the Private CAN Low Circuit for an open or high resistance.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  6. CHECK FOR OTHER DTCS 
    1. Refer to the recorded DTCs.

      Is the U0075 DTC also active or pending in PCM-2?

      Yes 

      • Low Battery voltage or a Battery disconnect could cause this DTC to set in both PCM's. Verify that the Battery was not disconnected and that the Battery voltage is to the proper level. If there are no issues with the Battery voltage, check the PCM powers and grounds for an open or high resistance.

      No 

      • Go To  7
  7. CHECK RELATED HARNESS CONNECTIONS 
    1. Disconnect all PCM-2 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-2 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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