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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 404 (Engine Controls And Fuel - 6.2L (LT4) - Diagnostic Information And Procedures (3 Of 3)) >> Diagnostic Information And Procedures >> DTC P1176 or P1177 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT5. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle - Off
    2. NOTE:

    Additional DTCs will set when disconnecting the components.

  2. Disconnect the electrical connector at one of the following components, depending on the DTC that is set:
    • {P1176} B150 Fuel Tank Pressure Sensor
    • {P1177} B47 Fuel Pressure Sensor
  3. Ignition - On/Vehicle - In Service Mode
  4. Verify the scan tool parameter:
    • {P1176} Fuel Pump Power Control Module 5V Reference = 5.01 V
    • {P1177} Fuel Pump Power Control Module 5V Reference 2 = 5.01 V
    • If the specified state after disconnecting a component from the circuit 

      Test or replace the component: The component that was disconnected last.

    • Go to next step: If not the specified state after disconnecting a component from the circuit 
  5. Test for 4.8 to 5.2 V between the test points:
    • {P1176} 5 V Reference circuit terminal 3@Component harness & Ground
    • {P1177} 5 V Reference circuit terminal 1@Component harness & Ground
    • If less than 4.8 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K111 Fuel Pump Power Control Module
    3. Test for infinite resistance between the test points:
      • {P1176} 5 V Reference circuit terminal 39 @Control module harness & Ground
      • {P1177} 5 V Reference circuit terminal 19 @Control module harness & 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:
      • {P1176} 5 V Reference circuit terminal 39 @Control module harness & 5 V Reference circuit terminal 3@Component harness
      • {P1177} 5 V Reference circuit terminal 19 @Control module harness & 5 V Reference circuit terminal 1@Component harness
      • If greater than 2 ohms - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K111 Fuel Pump Power Control Module
    • If greater than 5.2 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K111 Fuel Pump Power Control Module
    3. Ignition - On/Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:
      • {P1176} 5 V Reference circuit terminal 39 @Control module harness & Ground
      • {P1177} 5 V Reference circuit terminal 19 @Control module harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K111 Fuel Pump Power Control Module
    • Go to next step: If between 4.8 and 5.2 V 
  6. All OK.
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