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Home >> Chevrolet >> 2018 >> Suburban 3500 HD LT >> Repair and Diagnosis >> External Pages >> Different car >> Section 2 (Engine Controls And Fuel - 5.3L (L83) Or 6.2L (L86) - DTC P0010 To DTC P0442) >> Diagnostic Information And Procedures >> DTC P0178 Or P0179: Fuel Composition Sensor Circuit >> Circuit/System Testing

Circuit/System Testing

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  1. Verify that there are no contaminants, water, or too high of a concentration of ethanol in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis and the J44175 - A  Instruction Manual.
  2. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B198 Fuel Composition Sensor. It may take up to 2 min for all vehicle systems to power down.
  3. Test for less than 5 Ω between the ground circuit terminal 2 and ground.
    • If 5 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step : If less than 5 Ω 
  4. Ignition ON.
  5. Verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.
    • If the test lamp does not illuminate and the circuit fuse is OK 
    1. Ignition OFF, remove the test lamp.
    2. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF, remove the test lamp.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance, replace the B198 Fuel Composition Sensor.
    • Go to next step : If the test lamp illuminates 
  6. Remove the test lamp, ignition ON.
  7. Test for 4.8 - 5.2 V between the signal circuit terminal 3 and ground.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the signal circuit and ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
    2. Ignition ON.
    3. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • Go to next step : If between 4.8 - 5.2 V 
  8. Ignition OFF, connect the J 38522 - A  Variable Signal Generator as instructed below :
    1. Connect the red lead to the signal circuit terminal 3 at the B198 Fuel Composition Sensor harness connector.
    2. Connect the battery voltage supply lead to B+.
    3. Connect the black lead to ground.
    4. Set the signal to 5 V.
    5. Set the frequency to 60 Hz.
    6. Set the Duty Cycle to Normal.
    7. Ignition ON.
  9. Verify the scan tool Fuel Composition Sensor parameter is at 60 Hz.
    • If not at 60 Hz 

      Replace the K20 Engine Control Module.

    • Go to next step : If at 60 Hz 
  10. Test or replace the B198 Fuel Composition Sensor.
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