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Home >> Cadillac >> 2021 >> CT4 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (Engine Controls And Fuel - 2.7L (L3B) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0201-P0204, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P1248, P1249, P124A, P124B, P2147, P2148, P2150, P2151, P2153, P2154, P2156, or P2157 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.

Test 1

  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: X160 Inline Harness Connector
  3. Ignition - On / Vehicle - In Service Mode
    4. NOTE:

    Testing for steps 4 to 5 is performed on the control module K20 side of the harness connector.

  4. Verify a test lamp does not turn On between the test points:
    • {Q17A Fuel Injector 1} Control circuit terminal 10 & Ground
    • {Q17B Fuel Injector 2} Control circuit terminal 15 & Ground
    • {Q17C Fuel Injector 3} Control circuit terminal 14 & Ground
    • {Q17D Fuel Injector 4} Control circuit terminal 13 & Ground
    • If the test lamp turns On - Repair the short to voltage on the circuit. 
    • Go to next step: If the test lamp does not turn On 
  5. Test for 50 V (±5 V) between the test points:
    • {Q17A Fuel Injector 1} Control circuit terminal 10 & Ground
    • {Q17B Fuel Injector 2} Control circuit terminal 15 & Ground
    • {Q17C Fuel Injector 3} Control circuit terminal 14 & Ground
    • {Q17D Fuel Injector 4} Control circuit terminal 13 & Ground
    • If not the specified value 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: X3 @ K20 Engine Control Module
    3. Test for infinite resistance between the test points:
      • {Q17A Fuel Injector 1} Control circuit terminal 10 & Ground
      • {Q17B Fuel Injector 2} Control circuit terminal 15 & Ground
      • {Q17C Fuel Injector 3} Control circuit terminal 14 & Ground
      • {Q17D Fuel Injector 4} Control circuit terminal 13 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 ohms between the test points:
      • {Q17A Fuel Injector 1} Control circuit terminal 10 @ X160 Inline Harness Connector & Terminal 69 @ Control module harness
      • {Q17B Fuel Injector 2} Control circuit terminal 15 @ X160 Inline Harness Connector & Terminal 51 @ Control module harness
      • {Q17C Fuel Injector 3} Control circuit terminal 14 @ X160 Inline Harness Connector & Terminal 71 @ Control module harness
      • {Q17D Fuel Injector 4} Control circuit terminal 13 @ X160 Inline Harness Connector & Terminal 49 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • Replace the component: K20 Engine Control Module
    • Go to next step: If the specified value 
  6. Test for 0.05 to 0.12 V between the test points:
    • {Q17A Fuel Injector 1} Control circuit terminal 2 & Ground
    • {Q17B Fuel Injector 2} Control circuit terminal 7 & Ground
    • {Q17C Fuel Injector 3} Control circuit terminal 6 & Ground
    • {Q17D Fuel Injector 4} Control circuit terminal 4 & Ground
    • If less than 0.05 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: X3 @ K20 Engine Control Module
    3. Test for infinite resistance between the test points:
      • {Q17A Fuel Injector 1} Control circuit terminal 2 & Ground
      • {Q17B Fuel Injector 2} Control circuit terminal 7 & Ground
      • {Q17C Fuel Injector 3} Control circuit terminal 6 & Ground
      • {Q17D Fuel Injector 4} Control circuit terminal 4 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 ohms between the test points:
      • {Q17A Fuel Injector 1} Control circuit terminal 2 @ X160 Inline Harness Connector & Terminal 70 @ Control module harness
      • {Q17B Fuel Injector 2} Control circuit terminal 7 @ X160 Inline Harness Connector & Terminal 52 @ Control module harness
      • {Q17C Fuel Injector 3} Control circuit terminal 6 @ X160 Inline Harness Connector & Terminal 72 @ Control module harness
      • {Q17D Fuel Injector 4} Control circuit terminal 4 @ X160 Inline Harness Connector & Terminal 50 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • Replace the component: K20 Engine Control Module
    • If greater than 0.12 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: X3 @ K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:
      • {Q17A Fuel Injector 1} Control circuit terminal 2 & Ground
      • {Q17B Fuel Injector 2} Control circuit terminal 7 & Ground
      • {Q17C Fuel Injector 3} Control circuit terminal 6 & Ground
      • {Q17D Fuel Injector 4} Control circuit terminal 4 & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K20 Engine Control Module
    • Go to next step: If between 0.05 and 0.12 V 
  7. Ignition/Vehicle - Off
    8. NOTE:

    Testing for steps 7 to 8 is performed on the component side of the harness connector.

  8. Test for less than 3 ohms between the test points:
    • {Q17A Fuel Injector 1} Control circuit terminal 10 & Control circuit terminal 2
    • {Q17B Fuel Injector 2} Control circuit terminal 15 & Control circuit terminal 7
    • {Q17C Fuel Injector 3} Control circuit terminal 14 & Control circuit terminal 6
    • {Q17D Fuel Injector 4} Control circuit terminal 13 & Control circuit terminal 4
    • If 3 ohms or greater 
    1. Disconnect the appropriate electrical connector: Q17 Fuel Injector
    2. Test for less than 2 ohms between the test points:
      • {Q17A Fuel Injector 1} Control circuit terminal 2 @ X160 Inline Harness Connector & Control circuit terminal 1 @ Component harness
      • {Q17B Fuel Injector 2} Control circuit terminal 7 @ X160 Inline Harness Connector & Control circuit terminal 1 @ Component harness
      • {Q17C Fuel Injector 3} Control circuit terminal 6 @ X160 Inline Harness Connector & Control circuit terminal 1 @ Component harness
      • {Q17D Fuel Injector 4} Control circuit terminal 4 @ X160 Inline Harness Connector & Control circuit terminal 1 @ Component harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • Go to next step: If less than 2 ohms
    3. Test for less than 2 ohms between the test points:
      • {Q17A Fuel Injector 1} Control circuit terminal 10 @ X160 Inline Harness Connector & Control circuit terminal 2 @ Component harness
      • {Q17B Fuel Injector 2} Control circuit terminal 15 @ X160 Inline Harness Connector & Control circuit terminal 2 @ Component harness
      • {Q17C Fuel Injector 3} Control circuit terminal 14 @ X160 Inline Harness Connector & Control circuit terminal 2 @ Component harness
      • {Q17D Fuel Injector 4} Control circuit terminal 13 @ X160 Inline Harness Connector & Control circuit terminal 2 @ Component harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: Q17 Fuel Injector
    • Go to next step: If less than 3 ohms 
  9. Test or replace the component: Q17 Fuel Injector

Test 2

    NOTE:

    Testing for steps 1 to 4 is performed at the connector X3 of the control module K20.

  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: X3 @ K20 Engine Control Module
  3. Disconnect the appropriate electrical connector: Q17 Fuel Injector
  4. Test for infinite resistance between the test points:
    • {Q17A Fuel Injector 1} Control circuit terminal 69 @ Control module harness & Control circuit terminal 70 @ Control module harness
    • {Q17B Fuel Injector 2} Control circuit terminal 51 @ Control module harness & Control circuit terminal 52 @ Control module harness
    • {Q17C Fuel Injector 3} Control circuit terminal 71 @ Control module harness & Control circuit terminal 72 @ Control module harness
    • {Q17D Fuel Injector 4} Control circuit terminal 49 @ Control module harness & Control circuit terminal 50 @ Control module harness
    • If less than infinite resistance 

      Repair the short between the circuits.

    • Go to next step: If infinite resistance 
  5. Test or replace the component: Q17 Fuel Injector
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