CTS 2006-2007, CTS-V 2005-2007, DTS 2006-2007

Heated Oxygen Sensor

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Operation



The Heated Oxygen Sensor (HO2S) heater reduces the time required for the oxygen sensor to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The Engine Control Module (ECM) controls the heater operation by first modulating the control circuit to ground when the sensors are cold. This prevents the possibility of thermal shock to the sensor, from condensation build-up on the sensor, by controlling the sensors rate of heating. After a predetermined amount of time, the ECM commands the heaters ON continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to ground, to maintain a desired temperature.

The ECM controls the heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is more than a predetermined value when the circuit is commanded ON, this DTC sets

Removal & Installation



2.8L & 3.6L Engines
Bank 1 Sensor 1

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
    NOTE
    Bank 1 is the right bank.

  2.  
  3. Turn the ignition OFF.
  4.  
  5. Disconnect the HO2S electrical connector.
  6.  
  7. Remove the HO2S electrical connector from the wiring harness bracket.
  8.  
  9. Raise and support the vehicle.
  10.  
  11. Remove the HO2S from the catalytic converter.

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensors (HO2S) Bank 1 Sensor 1 removal

  12.  

To install:

  1. Install the HO2S to the catalytic converter.
  2.  
  3. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  4.  
  5. Lower the vehicle.
  6.  
  7. Install the HO2S electrical connector to the wiring harness bracket.
  8.  
  9. Connect the HO2S electrical connector.
  10.  

Bank 1 Sensor 2

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
    NOTE
    Bank 1 is the right bank.

  2.  
  3. Turn the ignition OFF.
  4.  
  5. Raise and support the vehicle.
  6.  
  7. Disconnect the HO2S electrical connector.

    Click image to see an enlarged view

    Fig. Disconnect the HO2S electrical connector. Bank 1 Sensor 2

  8.  
  9. Remove the HO2S wiring harness from the transmission case.
  10.  
  11. Remove the HO2S.
  12.  

To install:

  1. Install the HO2S.
  2.  
  3. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  4.  
  5. Connect the HO2S electrical connector.
  6.  
  7. Install the HO2S wiring harness to the transmission case.
  8.  
  9. Lower the vehicle.
  10.  

Bank 2 Sensor 1

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the left side air inlet panel
  4.  
  5. Disconnect the HO2S electrical connector.
  6.  
  7. Remove the HO2S electrical connector from the wiring harness bracket.
  8.  
  9. Raise and support the vehicle.
  10.  
  11. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensors (HO2S) Bank 2 Sensor 1 removal

  12.  

To install:

  1. Install the HO2S.
  2.  
  3. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  4.  
  5. Lower the vehicle.
  6.  
  7. Install the HO2S electrical connector to the wiring harness bracket.
  8.  
  9. Connect the HO2S electrical connector.
  10.  
  11. Install the left side air inlet panel.
  12.  

Bank 2 Sensor 2

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Turn the ignition OFF.
  4.  
  5. Raise and support the vehicle.
  6.  
  7. Disconnect the HO2S electrical connector.
  8.  
  9. Remove the HO2S wiring harness from the transmission case.
  10.  
  11. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensors (HO2S) Bank 2 Sensor 2 removal

  12.  

To install:

  1. Install the HO2S.
  2.  
  3. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  4.  
  5. Connect the HO2S electrical connector.
  6.  
  7. Install the HO2S wiring harness to the transmission case.
  8.  
  9. Lower the vehicle.
  10.  

4.6L Engine
Bank 1 Sensor 1

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the fuel injector sight shield.
  4.  
  5. Remove the Connector Position Assurance (CPA) retainer.
  6.  
  7. Disconnect the engine harness electrical connector from the Heated Oxygen Sensor (HO2S).
  8.  
  9. Remove the HO2S clip from the secondary Air Injection (AIR) check valve hose bracket.
  10.  
  11. Raise and support the vehicle.
  12.  
  13. Support the rear of the frame with a tall screw type jack.
  14.  
  15. Remove the 4 rearward frame to body bolts (left side shown, right side similar).

    Click image to see an enlarged view

    Fig. Removal of the 4 rearward frame to body bolts

  16.  
  17. Lower the screw type jack approximately 1.5 inch. (4 cm) but not more than 3 inch (76 mm), allowing the rear of the frame to lower.
  18.  
  19. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensors (HO2S) Bank 1 Sensor 1 removal

  20.  

To install:

  1. If reusing the old HO2S, coat the threads with anti-sieze compound, GM P/N 12377953 or equivalent.
  2.  
  3. Install the HO2S.
  4.  
  5. Tighten the sensor to 30 ft. lbs. (41 Nm).
  6.  
  7. Raise the engine frame into position.
  8.  
  9. Install the 4 rearward frame to body bolts.
  10.  
  11. Tighten the bolts to 141 ft. lbs. (191 Nm).
  12.  
  13. Remove the screw type jack.
  14.  
  15. Install the HO2S clip to the AIR check valve hose bracket.
  16.  
  17. Connect the engine harness electrical connector to the HO2S.
  18.  
  19. Install the CPA retainer.
  20.  
  21. Install the fuel injector sight shield.
  22.  

Bank 1 Sensor 2

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the oxygen sensor wiring harness heat shield.
  4.  
  5. Disconnect the engine harness electrical connector from the heated oxygen sensor (HO2S).
  6.  
  7. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensors (HO2S) Bank 1 Sensor 2 removal

  8.  
  9. If reusing the old HO2S, coat the threads with anti-sieze compound, GM P/N 12377953 or equivalent.
  10.  
  11. Install the HO2S.
  12.  
  13. Tighten the sensor to 30 ft. lbs. (41 Nm).
  14.  
  15. Connect the engine harness electrical connector to the HO2S.
  16.  
  17. Install the oxygen sensor wiring harness heat shield.
  18.  

Bank 2 Sensor 1

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the air deflector
  4.  
  5. Remove the Connector Position Assurance (CPA) retainer.
  6.  
  7. Disconnect the engine harness electrical connector from the heated oxygen sensor (HO2S).
  8.  
  9. Remove the HO2S clip from the engine bracket.
  10.  
  11. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensors (HO2S) Bank 2 Sensor 1 removal

  12.  

To install:

  1. If reusing the old HO2S, coat the threads with anti-sieze compound, GM P/N 12377953 or equivalent.
  2.  
  3. Install the HO2S.
  4.  
  5. Tighten the sensor to 30 ft. lbs. (41 Nm).
  6.  
  7. Connect the engine harness electrical connector to the HO2S.
  8.  
  9. Install the CPA retainer.
  10.  
  11. Install the HO2S clip to the engine bracket.
  12.  
  13. Install the air deflector.
  14.  

5.7L & 6.0L Engines
Bank 1 Sensor 1

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise the vehicle.
  4.  
  5. Disconnect the Heated Oxygen Sensor (HO2S) electrical connector.
  6.  
  7. Remove any wire harness retainers and note the wire harness routing for reassembly.
  8.  
  9. Carefully remove the HO2S.
  10.  

To install:

  1. Coat the threads of the HO2S with the anti-seize compound P/N 5613695, or the equivalent if necessary.
  2.  
  3. Install the HO2S.
  4.  
  5. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  6.  
  7. Connect the HO2S electrical connector.
  8.  
  9. Route and attach the wire harness as noted during disassembly.
  10.  
  11. Lower the vehicle.
  12.  

Bank 1 Sensor 2

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise the vehicle.
  4.  
  5. Disconnect the HO2S electrical connector. Note the harness routing and retainers for reassembly.
  6.  
  7. Remove the HO2S.

    Click image to see an enlarged view

    Fig. Heated Oxygen Sensors (HO2S) Bank 1 Sensor 2 removal

  8.  

To install:

  1. Install the HO2S.
  2.  
  3. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  4.  
  5. Connect the HO2S electrical connector. Ensure that the harness is routed and retained as noted during disassembly.
  6.  
  7. Lower the vehicle.
  8.  

Bank 2 Sensor 1

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise the vehicle.
  4.  
  5. Disconnect the HO2S electrical connectors. Note the harness routing and retainers for reassembly.
  6.  
  7. Remove the right side catalytic converter.
  8.  
  9. Remove the HO2S.
  10.  

To install:

  1. Coat the threads of the HO2S with the anti-seize compound P/N 5613695, or the equivalent if necessary
  2.  
  3. Install the HO2S.
  4.  
  5. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  6.  
  7. Install the right side catalytic converter.
  8.  
  9. Connect the HO2S electrical connector. Ensure that the harness is routed and retained as noted during disassembly.
  10.  
  11. Lower the vehicle.
  12.  

Bank 2 Sensor 2

NOTE
Remove the Heated Oxygen Sensors (HO2S) with the engine temperature above 48°C (120°F). Otherwise the HO2S may be difficult to remove.

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Raise the vehicle.
  4.  
  5. Disconnect the HO2S electrical connector. Note the harness routing and retainers for reassembly.
  6.  
  7. Remove the HO2S.
  8.  

To install:

  1. Coat the threads of the HO2S with the anti-seize compound P/N 5613695, or the equivalent if necessary.
  2.  
  3. Install the HO2S.
  4.  
  5. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  6.  
  7. Connect the HO2S electrical connector. Ensure that the harness is routed and retained as noted during disassembly.
  8.  
  9. Lower the vehicle.
  10.  

Testing



  1. If any HO2S heater DTCs are set, perform those diagnostics first.
  2.  
  3. Allow the engine to reach operating temperature.
  4.  
  5. Engine running, observe the affected HO2S parameter with a scan tool.
    1. The pre-catalyst oxygen sensors value should vary from below 200 mV to above 800 mV and respond to fueling changes.
    2.  
    3. The post-catalyst oxygen sensors value should change more than 200 mV when the throttle is quickly cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM for 30 seconds.
    4.  

  6.  
  7. The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination:

    A silicon contaminated HO2S
     
    Fuel contamination
     
    Engine oil consumption
     
    Engine coolant consumption
     

  8.  
  9. Engine running, observe the DTC information with a scan tool. DTCs P0153, P0154, P1153 or P2A03 should not set.
  10.  
  11. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
    NOTE
    All modules must be powered down or misdiagnosis may result.

  12.  
  13. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
  14.  
  15. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
  16.  
  17. Ignition OFF, measure for less than 5 ohms resistance between the appropriate HO2S low signal circuit terminal A and ground.
  18.  
  19. If more than the specified range, test the appropriate HO2S low signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  20.  
  21. Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
  22.  
  23. If more than the specified value, test the appropriate HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  24.  
  25. If less than the specified value, test the appropriate HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  26.  
  27. Ignition ON, install a 3A fused jumper wire at the HO2S high signal circuit terminal B. Toggle the jumper wire between the HO2S low signal circuit terminal A and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.
  28.  
  29. If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
  30.  
  31. If all circuits test normal, replace the appropriate HO2S.
  32.  

 
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