Solstice 2006-2008, Sky 2007-2008

Heated Oxygen Sensor

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Operation



Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Engine Control Module (ECM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the ECM operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust stream more quickly and accurately than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a signal voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant signal voltage. The ECM monitors the voltage variation on the signal circuit and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or reversing the direction of the current flow to the pumping cell. By measuring the direction and amount of current required to maintain the signal voltage, the ECM can determine the concentration of oxygen in the exhaust. The signal voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the system is lean, the oxygen level will be high and the lambda value will be high, or more than 1. When the system is rich, the oxygen level is low and the lambda value will be low, or less than 1. The ECM uses this information to maintain the proper air/fuel ratio.

Removal & Installation



2.0L (LNF) Engine Front (1) And Rear (2)

WARNING
The oxygen sensor uses a permanently attached pigtail and connector. Do not remove the pigtail from the oxygen sensor. Damage to or removal of the pigtail connector could affect proper operation of the oxygen sensor. The use of excessive force may damage the threads in the exhaust manifold/pipe.


NOTE
The Heated Oxygen Sensors (HO2S) may be difficult to remove when the engine temperature is less than 48°C (120°F).

  1. Open the hood.
  2.  
  3. Remove the Connector Position Assurance (CPA) retainer.
  4.  
  5. Disconnect the HO2S electrical connector from the engine wiring harness electrical connector.
  6.  
  7. Raise and support the vehicle for removal of the rear HO2S only.
  8.  
  9. Using an approved oxygen sensor wrench remove the HO2S.

    Click image to see an enlarged view

    Fig. Front (1) Heated Oxygen Sensors 2.0L (LNF) Engine



    Click image to see an enlarged view

    Fig. Rear (2) Heated Oxygen Sensors 2.0L (LNF) Engine

  10.  

To install:


NOTE
A special anti-seize compound is used on the HO2S threads. The compound consists of a liquid graphite and glass beads. The graphite will burn away, but the glass beads will remain, making the sensor easier to remove. New or service sensors will have the compound applied to the threads. If a sensor is removed and is to be reinstalled, the threads must have an anti-seize compound applied before installation.

  1. If reinstalling the old HO2S, coat the threads with anti-seize compound.
  2.  
  3. Using an approved oxygen sensor wrench install the HO2S.
  4.  
  5. Tighten the HO2S to 31 ft. lbs. (42 Nm).
  6.  
  7. Lower vehicle if rear HO2S was installed.
  8.  
  9. Connect the HO2S electrical connector.
  10.  
  11. Install the CPA retainer.
  12.  
  13. Close the hood.
  14.  

2.4L (LE5) Engine Front (1) And Rear (2)

WARNING
The oxygen sensor uses a permanently attached pigtail and connector. Do not remove the pigtail from the oxygen sensor. Damage to or removal of the pigtail connector could affect proper operation of the oxygen sensor. The use of excessive force may damage the threads in the exhaust manifold/pipe.


NOTE
The Heated Oxygen Sensors (HO2S) may be difficult to remove when the engine temperature is less than 48°C (120°F).

  1. Open the hood.
  2.  
  3. Remove the Connector Position Assurance (CPA) retainer.
  4.  
  5. Disconnect the HO2S electrical connector.
  6.  
  7. Remove the HO2S electrical connector clip from the junction block bracket.
  8.  
  9. Raise and support the vehicle for removal of the rear HO2S only.
  10.  
  11. Using an approved oxygen sensor wrench remove the HO2S.

    Click image to see an enlarged view

    Fig. Front (1) and Rear (2) Heated Oxygen Sensors

  12.  

To install:


NOTE
A special anti-seize compound is used on the HO2S threads. The compound consists of a liquid graphite and glass beads. The graphite will burn away, but the glass beads will remain, making the sensor easier to remove. New or service sensors will have the compound applied to the threads. If a sensor is removed and is to be reinstalled, the threads must have an anti-seize compound applied before installation.

  1. If reinstalling the old HO2S, coat the threads with anti-seize compound.
  2.  
  3. Using an approved oxygen sensor wrench install the HO2S.
  4.  
  5. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  6.  
  7. Lower vehicle if rear HO2S was installed.
  8.  
  9. Connect the HO2S electrical connector.
  10.  
  11. Install the CPA retainer.
  12.  
  13. Close the hood.
  14.  

Testing



Front Sensor
  1. Ignition OFF, disconnect the HO2S 1.
  2.  
  3. Ignition ON, test for 2.9 volts between the HO2S 1 High Signal circuit terminal no. 6 and ground.
    1. If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the Electronic Control Module (ECM).
    2.  
    3. If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
    4.  

  4.  
  5. Ignition ON, test for 2.5 volts between the HO2S 1 low signal circuit terminal no. 2 and ground
    1. If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    2.  
    3. If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
    4.  

  6.  
  7. Ignition ON, test for 2.8 volts between the HO2S 1 Output Pump Current circuit terminal no. 1 and ground.
    1. If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    2.  
    3. If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
    4.  

  8.  
  9. Ignition ON, test for 2.8 volts between the HO2S 1 Input Pump Current circuit terminal no. 5 and ground.
    1. If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    2.  
    3. If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
    4.  

  10.  
  11. Ignition OFF, disconnect the ECM connector C1.
  12.  
  13. Ignition OFF, test for infinite ohms between each HO2S 1 circuit terminal no. and all other HO2S 1 circuit terminals.
    1. If less than the specified value, repair as necessary.
    2.  

  14.  
  15. If the ECM and all circuits test normal, replace the HO2S 1.

    Click image to see an enlarged view

    Fig. Front HO2S (1) Electrical connector

  16.  

Rear Sensor
  1. If present clear the DTCs with a scan tool.
  2.  
  3. Operate the vehicle within the conditions for running and setting the DTC. The DTC should not set.
    NOTE
    All modules must be powered down or misdiagnosis may result.

  4.  
  5. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
  6.  
  7. Ignition OFF, disconnect the harness connector at the HO2S 2.
  8.  
  9. Ignition OFF, measure for less than 5 ohms resistance between the HO2S 2 low signal circuit terminal no. A and ground.
    1. If more than the specified range, test the HO2S 2 low signal circuit for an open/high resistance. If the circuit tests normal, replace the Electronic Control Module (ECM).
    2.  

  10.  
  11. Ignition ON, verify the scan tool HO2S 2 parameter is approximately 450 mV.
    1. If more than the specified value, test the HO2S 2 high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    2.  
    3. If less than the specified value, test the HO2S 2 high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
    4.  

  12.  
  13. Ignition ON, install a 3A fused jumper wire at the HO2S 2 high signal circuit terminal no. B. Toggle the jumper wire between the HO2S 2 low signal circuit terminal no. A and battery voltage. Verify the scan tool HO2S 2 parameter toggles between 0 mV and approximately 1,000 mV.
  14.  
  15. If the scan tool HO2S 2 parameter does not toggle correctly, test the HO2S 2 high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
  16.  
  17. If all circuits test normal, replace the HO2S  2.

    Click image to see an enlarged view

    Fig. Rear HO2S (2) Electrical connector

  18.  

 
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