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Home >> Alfa Romeo >> 2019 >> Giulia Base, AWD >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Body Control Module (BCM) - DTCS U1703-86 To U1A56-87 >> DTC Troubleshooting >> U1801-08-Lin 1-Bus Signal/Message Failure >> Diagnostic Test

Diagnostic Test

  1. CHECK FOR AN ACTIVE DTC 
    1. With the scan tool, read Body Control Module (BCM) DTCs and record on the repair order.
    2. Record the Environmental Data.
    3. With the scan tool, erase DTCs.
    4. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    5. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      • Go To  2

      No 

  2. CHECK THE INTELLIGENT BATTERY SENSOR (IBS) FOR AN INTERNAL SHORT 
    1. Turn the ignition off.
    2. Disconnect the IBS harness connector.
    3. Turn the ignition on.
    4. With the scan tool, erase DTCs.
    5. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    6. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      • Go To  3

      No 

  3. CHECK THE LIGHT RAIN SENSING MODULE (LRSM) FOR AN INTERNAL SHORT 
    1. Turn the ignition off.
    2. Disconnect the LRSM harness connector.
    3. Turn the ignition on.
    4. With the scan tool, erase DTCs.
    5. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    6. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      • Go To  4

      No 

  4. CHECK THE ELECTRONIC OVERHEAD MODULE (EOM) FOR AN INTERNAL SHORT 
    1. Turn the ignition off.
    2. Disconnect the EOM harness connector.
    3. Turn the ignition on.
    4. With the scan tool, erase DTCs.
    5. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    6. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      • Go To  5

      No 

  5. CHECK THE SEAT BELT REMINDER INDICATOR FOR AN INTERNAL SHORT 
    1. Turn the ignition off.
    2. Disconnect the Seat Belt Reminder Indicator harness connector.
    3. Turn the ignition on.
    4. With the scan tool, erase DTCs.
    5. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    6. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      • Go To  6

      No 

  6. CHECK THE ALARM SILENT UNIT (ASU) FOR AN INTERNAL SHORT 
    1. Turn the ignition off.
    2. Disconnect the ASU harness connector.
    3. Turn the ignition on.
    4. With the scan tool, erase DTCs.
    5. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    6. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      • Go To  7

      No 

  7. CHECK THE (D401) LIN BUS 1 CIRCUIT FOR A SHORT TO VOLTAGE 
    1. Turn the ignition off.
    2. Disconnect the BCM C6/F harness connector.
    3. Turn the ignition on.
    4. Measure the voltage on the (D401) LIN Bus 1 circuit at BCM C6/F harness connector - terminal 2.

      Is there any voltage present?

      Yes 

      No 

      • Go To  8
  8. CHECK THE (D401) LIN BUS 1 CIRCUIT FOR A SHORT TO GROUND 
    1. Turn the ignition off.
    2. Check for continuity between ground and the (D401) LIN Bus 1 circuit at BCM C6/F harness connector - terminal 2.

      Is there continuity between ground and the (D401) LIN Bus 1 circuit?

      Yes 

      No 

      • Go To  9
  9. CHECK RELATED HARNESS CONNECTIONS 
    1. Disconnect all BCM 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.
      • Perform a terminal drag test on each connector terminal to verify proper terminal tension.

      Repair any conditions that are found.

    5. Connect all BCM 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. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    10. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      No