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Home >> Cadillac >> 2021 >> CT5 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 5 (Engine Controls And Fuel - 3.0L (LGY) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0090-P0092, P00C8, P00C9, or P00CA >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: @ G18 Fuel Pump - High Pressure
  3. Connect a test lamp between the test points: Control circuit terminal 1 & Control circuit terminal 2
  4. Engine - Idling - At normal operating temperature
  5. Increase the engine speed slowly to 3500 RPM and then back to idle. Fuel Pressure Regulator - On and Off

    Verify the test lamp turns On and changes brightness.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: X4 @ K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:
      • Control circuit terminal 1 @ Component harness & Ground
      • Control circuit terminal 2 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for infinite resistance between the test points:
      • Control circuit terminal 1 @ Component harness & Ground
      • Control circuit terminal 2 @ Component harness & Ground
    7. Test for infinite resistance between the test points:
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    8. Test for less than 2 Ω between the test points:
      • Control circuit terminal 2 @ Component harness & Terminal 16 @ Control module harness
      • Control circuit terminal 1 @ Component harness & Terminal 32 @ Control module harness
      • If 2 Ω or greater - Repair the open/high resistance in the circuit.
      • If less than 2 Ω - Replace the component: K20 Engine Control Module
    • Go to next step: If the test lamp turns On and changes brightness 
  6. Test or replace the component: G18 Fuel Pump - High Pressure