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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> 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 Power Up >> Circuit/System Testing

Circuit/System Testing

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 each of the X84 Data Link Connector ground circuit terminals listed below and B+.
    • Terminal 4
    • Terminal 5
    • 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. Ignition ON/Vehicle In Service Mode.
  4. Verify a test lamp illuminates between the B+ circuit terminal 16 at the X84 Data Link Connector and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test for an open/high resistance in the B+ circuit.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found
    2. Verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Test for a short to ground in the B+ circuit.
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Refer to the scan tool user guide.
    • Go to next step: If the test lamp illuminates 
  5. Refer to the scan tool user guide.
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