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Home >> Alfa Romeo >> 2019 >> Giulia Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> 2.0L - DTCS P0480-00 To P0687-00 >> DTC Troubleshooting >> P0641-00-Sensor Reference Voltage "A" Circuit/Open >> Diagnostic Test

Diagnostic Test

  1. CHECK FOR AN ACTIVE DTC 
    NOTE:

    Improperly installed aftermarket accessories can cause this DTC to set. Check for any improperly installed aftermarket accessories before continuing with this test.

    1. Turn the ignition on.
    2. With the scan tool, read DTCs and record on the repair order.

      Is the DTC active or pending?

      Yes 

      • Go To  2

      No 

  2. CHECK THE SENSORS THAT SHARE THE 5-VOLT SUPPLY 
    1. IMPORTANT - FOLLOW THIS PROCEDURE EXACTLY WHEN CHECKING THE FOLLOWING COMPONENTS: 
      • Turn the ignition off before disconnecting each component.
      • After a component has been disconnected, turn the ignition on and measure the voltage on the Primary 5-Volt Supply circuit at the component harness connector.
      • If the 5-Volt Supply voltage returns to 5.0 volts after disconnecting a component, the component that was disconnected is faulty.
      • If the voltage remains low after disconnecting a component, then the disconnected component is not the problem.
      • Leave each component disconnected and move on to the next until the faulty component is discovered or all components have been disconnected. Disconnect only one component at a time during this step.
    2. Disconnect the MAP Sensor harness connector and check the Primary 5-Volt Supply circuit voltage.
    3. Disconnect the Boost Pressure Sensor harness connector and check the Primary 5-Volt Supply circuit voltage.
    4. Disconnect the Crankcase Pressure Sensor harness connector and check the Primary 5-Volt Supply circuit voltage.
    5. Disconnect the EGR Valve harness connector and check the Primary 5-Volt Supply circuit voltage.
    6. Disconnect the CKP Sensor harness connector and check the Primary 5-Volt Supply circuit voltage.
    7. Disconnect the Low Fuel Pressure Sensor harness connector and check the Primary 5-Volt Supply circuit voltage.
    8. Disconnect the APP Sensor harness connector and check the Primary 5-Volt Supply circuit voltage.

      Were any of the components determined to be at fault?

      Yes 

      • Replace the faulty component in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  3
  3. CHECK THE PRIMARY 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE 
    NOTE:

    All of the components should still be disconnected during this test step.

    1. Measure the voltage on the Primary 5-Volt Supply circuit at the PCM harness connectors.

      Is the voltage reading above 5.2 volts?

      Yes 

      • Repair the Primary 5-Volt Supply circuit for a short to voltage.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  4
  4. CHECK THE PRIMARY 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND 
    1. Turn the ignition off.
      NOTE:

      All of the components should still be disconnected during this test step.

    2. Disconnect the PCM harness connectors from the PCM.
    3. Check for continuity between ground and the Primary 5-Volt Supply circuit at any of the harness connectors.

      Is there continuity between ground and the Primary 5-Volt Supply circuit(s)?

      Yes 

      • Repair the Primary 5-Volt Supply circuit for a short to ground.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  5
  5. CHECK RELATED PCM AND COMPONENT CONNECTIONS 
    1. Perform any Service Bulletins that apply.
    2. Disconnect all PCM harness connectors.
    3. Disconnect all related in-line harness connections (if equipped).
    4. Disconnect the related component harness connectors.
    5. 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.

    6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
    9. With the scan tool, erase DTCs.
    10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
    11. 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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