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Home >> Cadillac >> 2021 >> CT4 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 191 (Data Communications - Diagnostic Information And Procedures (3 Of 3)) >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Vehicle >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down.
  2. Verify a test lamp illuminates between the ground circuit terminal 5 at the X84 Data Link Connector and B+.
    • If the test lamp does not illuminate 

      Repair the open/high resistance in the ground circuit or ground connection.

    • Go to next step: If the test lamp illuminates 
  3. Refer to Circuit/System Testing.