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Home >> Cadillac >> 2017 >> CT6 Plug-In >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls And Fuel - 2.0L (LTG) - DTC P0010 To DTC P0443 >> Diagnostic Information and Procedures >> DTC P00F4-P00F6: Intake Air Humidity Sensor Circuit >> Circuit/System Testing
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Circuit/System Testing

NOTE: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Ignition Off and all vehicle systems Off, it may take up to 2 min. for all vehicle systems to power down. Disconnect the harness connector at the B75C Multifunction Intake Air sensor.
  2. Test for less than 5 Ω between the low reference circuit terminal 3 and ground.
    • If 5 Ω or greater 
    1. Disconnect the harness connector at the K20 Engine Control Module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open or high resistance in the circuit.
      • If less than 2 Ω replace the K20 Engine Control Module.
    • If less than 5 Ω 
  3. Test for less than 5 Ω between the ground circuit terminal 7 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 or high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 5 Ω 
  4. Ignition On.
  5. Verify that a test lamp illuminates between the ignition circuit terminal 5 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition Off, remove the test lamp and remove the fuse for the ignition voltage circuit.
    2. Test for less than 2 Ω in the ignition voltage 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 not open 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, the fuse for the ignition voltage circuit and disconnect all components on the circuit.
      NOTE: The ignition circuit may supply voltage to other components. Make sure to test all circuits and components for a short to ground that share the ignition circuit.
    2. Test for infinite resistance between the ignition voltage circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test all components connected to the ignition circuit, replace as necessary.
    • If a test lamp illuminates 
  6. Verify the scan tool Intake Air Humidity Sensor parameter is less than 1%.
    NOTE: The intake air temperature sensor 2 signal circuit is pulled up with low current voltage within the controller. Normally, a voltage near B+ can be measured on the circuit with a DMM, but the current will not be high enough to illuminate a test lamp.
    • If 1% or greater 
    1. Ignition Off, disconnect the harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the IAT 2 signal circuit terminal 8 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K20 Engine Control Module.
    • If less than 1% 
  7. Ignition Off, connect a 3 A fused jumper wire between the IAT 2 signal circuit terminal 8 and the low reference circuit terminal 3.
  8. Ignition On.
  9. Verify the scan tool Intake Air Humidity Sensor parameter is greater than 99%.
    • If 99% or less 
    1. Ignition Off, remove the jumper wire and disconnect the harness connector at the K20 Engine Control Module.
      NOTE: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.
    2. Ignition On.
    3. Test for less than 1 V between the IAT 2 signal circuit terminal 8 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V.
    4. Ignition Off.
    5. 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 99% 
  10. Test or replace the B75C Multifunction Intake Air sensor.
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