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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 135 (12 V Starting And Charging - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P26E4-P26E6 >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF and all vehicle systems OFF, disconnect the KR27C Engine Restart Relay. It may take up to 2 min for all vehicle systems to power down.
  2. Verify a test lamp illuminates between ground circuit terminal 86 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 6450 or ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Ignition on, connect a test lamp between the control circuit terminal 85 and ground.
  4. Verify the test lamp turns ON and OFF while commanding the Starter Drive ON and OFF with the scan tool.
    • If the test lamp is always OFF 
    1. Test circuit 4325 for a short to ground.
      • 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. Test circuit 4325 for an open/high resistance.
      • 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
    3. Replace the K20 Engine Control Module.
    • If the test lamp is always ON 
    1. Test circuit 4325 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found
    2. Replace the K20 Engine Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  5. Test or replace the KR27C Engine Restart Relay.
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