Cobalt 2006-2008, G5 2007

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. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, a ground is provided to the heater by the HO2S heater low control circuit through a low side driver within the Powertrain Control Module (PCM). The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM monitors the voltage on the HO2S heater low control circuit for heater fault diagnosis. If the PCM detects that the HO2S heater low control circuit voltage is not within a specified range, DTC P0030 sets for HO2S 1, or DTC P0036 sets for HO2S 2.

Removal & Installation



2.0L & 2.2L Engines
Heated Oxygen Sensor-1


Click image to see an enlarged view

Fig. Location of the heated oxygen sensor 1-2.0L & 2.2L engines


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.


WARNING
The use of excessive force may damage the threads in the exhaust manifold/pipe.


NOTE
The in-line connector and louvered end must be kept clear of grease, dirt or other contaminants. Avoid using cleaning solvents of any type. DO NOT drop or roughly handle the oxygen sensor.


NOTE
The oxygen sensor may be difficult to remove when the engine temperature is less than 120°F (48°C).

  1. Remove the exhaust manifold heat shield.
  2.  
  3. Disconnect the oxygen sensor harness connector.
  4.  
  5. Remove the oxygen sensor using the oxygen sensor wrench, J 39194-C.
  6.  

To install:


NOTE
A special anti-seize compound is used on the oxygen sensor 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. Coat the threads of the oxygen sensor with anti-seize compound GM P/N 12377953, or equivalent, if necessary.
  2.  
  3. Install the oxygen sensor. Tighten the oxygen sensor to 22 ft. lbs. (30 Nm).
  4.  
  5. Connect the oxygen sensor harness connector.
  6.  
  7. Install the exhaust manifold heat shield. Tighten the heat shield studs to 16 ft. lbs. (22 Nm).
  8.  

Heated Oxygen Sensor-2


Click image to see an enlarged view

Fig. Remove the wheel drive shaft heat shield-2.0L & 2.2L engines

  1. Raise and safely support the vehicle.
  2.  
  3. Remove the wheel drive shaft heat shield bolt at the transaxle mount bracket.
  4.  
  5. Remove the drive shaft heat shield bolt at the engine block.
  6.  
  7. Remove the wheel drive shaft heat shield.

    Click image to see an enlarged view

    Fig. Location of the heated oxygen sensor 2-2.0L & 2.2L engines

  8.  
  9. Note the routing of the Heated Oxygen Sensor (HO2S) electrical harness.
  10.  
  11. Disconnect the HO2S electrical connector (2), in the engine compartment.
  12.  
  13. Carefully bend the edge of the channel on the LH side of the exhaust heat shield outboard, just enough to release the HO2S electrical harness (1).
    WARNING
    Do not remove the pigtail from either the heated oxygen sensor (HO2S) or the oxygen sensor (O2S). Removing the pigtail or the connector will affect sensor operation. Handle the oxygen sensor carefully. Do not drop the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Do not use cleaning solvents of any type. Do not repair the wiring, connector or terminals. Replace the oxygen sensor if the pigtail wiring, connector, or terminal is damaged. This external clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance.

  14.  

The following guidelines should be used when servicing the heated oxygen sensor:



Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance
 
Do not damage the sensor pigtail and harness wires in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems.
 
Ensure the sensor or vehicle lead wires are not bent sharply or kinked. Sharp bends or kinks could block the reference air path through the lead wire.
 
Do not remove or defeat the oxygen sensor ground wire, where applicable. Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance.
 
Ensure that the peripheral seal remains intact on the vehicle harness connector in order to prevent damage due to water intrusion. The engine harness may be repaired using an appropriate crimp and splice seal terminal repair kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed.
 

  1. Remove the oxygen sensor using the oxygen sensor wrench, J 39194.
  2.  
  3. Lower the HO2S electrical harness away from the underbody.
  4.  

To install:


NOTE
A special anti-seize compound is used on the oxygen sensor 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, GM P/N 12377953, or equivalent.
  2.  
  3. Carefully install the HO2S to the pipe.
  4.  
  5. Using the J 39194 , or equivalent, tighten the HO2S. Tighten the HO2S to 30 ft. lbs. (41 Nm).
  6.  
  7. Install the HO2S electrical harness into position as noted before removal.
    WARNING
    Use care when securing the HO2S electrical harness into the channel on the exhaust heat shield, to not pinch the wires.

  8.  
  9. Carefully bend the edge of the channel (1) on the LH side of the exhaust heat shield inboard, just enough to secure the HO2S electrical harness in the channel.
  10.  
  11. Connect the HO2S electrical connector (2).
  12.  
  13. Install the wheel drive shaft heat shield into position on the vehicle.
  14.  
  15. Install the wheel drive shaft heat shield bolt to the engine block. Tighten the bolt to 22 ft. lbs. (30 Nm).
  16.  
  17. Install the wheel drive shaft heat shield bolt to the transaxle mount bracket. Tighten the bolt to 89 inch lbs. (10 Nm).
  18.  
  19. Lower the vehicle.
  20.  

2.4L Engine
Sensor 1

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.


WARNING
The use of excessive force may damage the threads in the exhaust manifold/pipe.


NOTE
The in-line connector and louvered end must be kept clear of grease, dirt or other contaminants. Avoid using cleaning solvents of any type. DO NOT drop or roughly handle the oxygen sensor.


NOTE
The oxygen sensor may be difficult to remove when the engine temperature is less than 120°F (48°C).



Click image to see an enlarged view

Fig. Remove the exhaust manifold heat shield studs-2.4L engine

  1. Remove the exhaust manifold heat shield studs (2).
  2.  
  3. Remove the exhaust manifold heat shield (1).

    Click image to see an enlarged view

    Fig. Location of HO2S sensor 1 for the RPO MN5-2.4L engine

  4.  
  5. If equipped with Regular Production Option (RPO) MN5, perform the following steps:
    1. Remove the Connector Position Assurance (CPA) retainer.
    2.  
    3. Disconnect the engine harness electrical connector (2) from the HO2S.
    4.  
    5. Remove the HO2S connector clip from the thermostat housing.

      Click image to see an enlarged view

      Fig. Location of HO2S sensor 1 for the RPO M86-2.4L engine

    6.  

  6.  
  7. If equipped with RPO M86, perform the following steps:
    1. Remove the CPA retainer (2).
    2.  
    3. Disconnect the engine harness electrical connector (1) from the HO2S.
    4.  
    5. Remove the HO2S connector clip from the thermostat housing.
    6.  

  8.  
  9. Using the J 39194-C, remove the HO2S.
  10.  

To install:


NOTE
A special anti-seize compound is used on the heated oxygen sensor 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 replacement 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 prior to installation.

  1. If necessary, coat the threads of the HO2S with anti-seize compound GM P/N 12377953, Saturn P/N 21485279, or equivalent.
  2.  
  3. Using the J 39194-C, install the HO2S. Tighten the sensor to 31 ft. lbs. (42 Nm).
  4.  
  5. If equipped with RPO M86, perform the following steps:
    1. Connect the engine harness electrical connector to the HO2S.
    2.  
    3. Install the CPA retainer.
    4.  
    5. Install the HO2S connector clip to the thermostat housing.
    6.  

  6.  
  7. If equipped with RPO MN5, perform the following steps:
    1. Connect the engine harness electrical connector to the HO2S.
    2.  
    3. Install the CPA retainer.
    4.  
    5. Install the HO2S connector clip to the thermostat housing.
    6.  

  8.  
  9. Install the exhaust manifold heat shield.
  10.  
  11. Install the exhaust manifold heat shield studs. Tighten the studs to 16 ft. lbs. (22 Nm).
  12.  

Sensor 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.


WARNING
The use of excessive force may damage the threads in the exhaust manifold/pipe.


NOTE
The in-line connector and louvered end must be kept clear of grease, dirt or other contaminants. Avoid using cleaning solvents of any type. DO NOT drop or roughly handle the oxygen sensor.


NOTE
The oxygen sensor may be difficult to remove when the engine temperature is less than 120°F (48°C).



Click image to see an enlarged view

Fig. Location of HO2S sensor 2 for the RPO MN5-2.4L engine

  1. If equipped with Regular Production Option (RPO) MN5, perform the following steps:
    1. Remove the connector position assurance (CPA) retainer.
    2.  
    3. Disconnect the HO2S electrical connector lead from the engine harness electrical connector (4).

      Click image to see an enlarged view

      Fig. Location of HO2S sensor 2 for the RPO M86-2.4L engine

    4.  

  2.  
  3. If equipped with RPO M86, perform the following steps:
    1. Remove the CPA retainer (4).
    2.  
    3. Disconnect the HO2S connector lead from the engine harness electrical connector (5).
    4.  

  4.  
  5. Raise and support the vehicle.

    Click image to see an enlarged view

    Fig. Bend the heat shield trough down slightly until the HO2S lead can be removed-2.4L engine

  6.  
  7. Bend the heat shield trough (2) down slightly until the HO2S lead (1) can be removed.
  8.  
  9. Using the J 39194-C, remove the HO2S.
  10.  

To install:


NOTE
A special anti-seize compound is used on the heated oxygen sensor 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 replacement 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 prior to installation.

  1. If necessary, coat the threads of the HO2S with anti-seize compound GM P/N 12377953. Saturn P/N 21485279, or equivalent.
  2.  
  3. Using the J 39194-C, install the HO2S. Tighten the sensor to 31 ft. lbs. (42 Nm).
    WARNING
    Use care when securing the HO2S electrical lead into the trough on the exhaust heat shield, as not to pinch the lead.

  4.  
  5. Bend the heat shield trough (2) up until the HO2S lead (1) is secured.
  6.  
  7. Lower the vehicle.
  8.  
  9. If equipped with RPO M86, perform the following steps:
    1. Connect the HO2S connector lead to the engine harness electrical connector.
    2.  
    3. Install the CPA retainer.
    4.  

  10.  
  11. If equipped with RPO MN5, perform the following steps:
    1. Connect the HO2S electrical connector lead to the engine harness electrical connector.
    2.  
    3. Install the CPA retainer.
    4.  

  12.  

Testing





Click image to see an enlarged view

Fig. HO2S sensor 1 connector end view



Click image to see an enlarged view

Fig. HO2S sensor 2 connector end view

  1. With an OBD2 scan tool connected to the datalink port:
    1. Start the engine.
    2.  
    3. Wait 15 seconds to allow the heated oxygen sensor (HO2S) heater current to stabilize.
    4.  
    5. Observe the affected HO2S heater parameter with a scan tool.
    6.  
    7. The HO2S heater parameter should be within the specified range: 0.2-1.7 Amps.
    8.  

  2.  
  3. Replace the affected HO2S as necessary.
  4.  
  5. Probe for circuit voltage:
    1. Turn engine OFF.
    2.  
    3. Disconnect the affected HO2S.
    4.  
    5. Turn ON the ignition, with the engine OFF.
    6.  
    7. Probe the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side with a test lamp that is connected to a good ground.
    8.  
    9. The test lamp should illuminate.
    10.  

  6.  
  7. Test the ground circuit:
    1. Turn OFF the ignition.
    2.  
    3. Probe the HO2S heater low control circuit of the HO2S harness connector on the engine harness side with a test lamp connected to battery voltage.
    4.  
    5. With the ignition still OFF, observe the test lamp.
    6.  
    7. The test lamp should illuminate.
    8.  

  8.  

 
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