BMW Cars 1999-06

Oxygen Sensor 1

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Operation



Both OBD I and OBD II systems use an Oxygen (O 2 ) sensor upstream from the catalytic converter (pre catalytic converter) to monitor the engine's fuel mixture. The OBD II systems use a Heated Oxygen (HO 2 ) sensor located both before (pre catalytic converter) and after the catalytic converter (post catalytic converter). The advantage of the HO 2 is that it can reach operating temperature more quickly than a non heated sensor, allowing the Engine Control Module (ECM) to control the fuel injection more quickly, thus reducing emissions.

The post catalytic converter HO 2 sensor used on OBD II systems is used to monitor the operation of the pre catalytic converter HO 2 sensor.

The HO 2 and O 2 sensors compare the oxygen content of the outside air with the quantity of oxygen in the exhaust gasses. The sensor then generates a corresponding voltage signal used as an input to the ECM. On Bosch® systems, the mixture-too-rich voltage signal or low oxygen content is about 0.6 to 0.9 volts. The mixture-too-lean voltage signal or high oxygen content range is between 0.0 to 0.3 volts. During the transition from rich to lean or lean to rich, the voltage fluctuates between 0.6 to 0.9 volts and 0.0 to 0.3 volts.

During normal operation the HO 2 /O 2 sensor voltage should continuously fluctuate between 0.1-0.9 volts on Bosch® sensors and 0.1-4.9 volts on Siemens (NGK) sensors

If the voltage fails to fluctuate, or the sensor responses time is too slow (lazy), the following conditions are potential causes:



The openings on the sensor tip are blocked
 
The sensor could have been thermally overloaded
 
The sensor has been damaged by silicone contamination (sprays or sealants)
 
The sensor has been contaminated with fuel containing lead. Check the lead content using a PLUMBTESMO test strip
 
Improper electrical terminal resistance in the signal wire(s)
 
HO 2 sensor is too cold and cannot not reach ideal operating temperature, caused by an inoperative oxygen sensor heater (OBD II system)
 
The HO 2 /O 2 sensor control switched off by the ECM.
 
The HO 2 /O 2 sensor has been damaged with an electrical contact cleaner or an equivalent.
 

The contact cleaner spray can be drawn in through the sensor wires by capillary action caused by pressure differentials and during cool down. This can coat the sensor element and air passages reducing sensitivity or causing a control failure.

Removal & Installation




NOTE
Do not use any sealants that contain silicone to seal the intake area of an engine using Oxygen sensors. The silicone particles will not be consumed during combustion, thus the unburned particles will travel in the exhaust flow to the O 2 sensor. These particles can ultimately coat the sensor probe(s) and prevent or permanently damage the O 2 sensor operation. Additionally, do not use electrical contact cleaner (or its equivalent) in the area of the HO 2 sensor harness electrical connector(s) because it could lead to corrosion damage of the sensor.

  1. Raise and safely support the vehicle.
  2.  
  3. Disconnect the Oxygen O 2 sensor electrical connector.
  4.  
  5. Slide a 22mm ( 7 / 8 inch) boxed end wrench over the electrical connector and wiring and remove the O 2 sensor by turning it counterclockwise.
  6.  



Click image to see an enlarged view

Fig. Unplug the Oxygen sensor electrical connector, then slide a boxed end wrench over the sensor's connector and wiring



Click image to see an enlarged view

Fig. Remove the Oxygen sensor by turning it counterclockwise with the wrench

To install:

  1. Apply a light coat of a suitable anti-seize compound to the threads of the sensor. Make sure to not get any compound on the sensor's tip.
  2.  
  3. Torque the sensor to 40.6 ft. lbs. (55 Nm).
  4.  
  5. Reconnect the wiring.
  6.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
    NOTE
    The plug connection must be disconnected before the oxygen control sensor is removed. If the plug connection separation point is below the cover for the fuel injectors:



    Remove the lower section of microfilter housing.
     
    Remove the cover from fuel injectors.
     
    Unclip theoxygen control sensor cable from retainer.
     
    Disconnect the plug connection for the oxygen sensor.
     
    Remove the oxygen control sensor.

    Click image to see an enlarged view

    Fig. The removal and installation of the oxygen sensor

     

  2.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Disconnect the connector for the oxygen sensor.

    Click image to see an enlarged view

    Fig. Disconnect the connector for the oxygen sensor

  4.  
  5. Unclip the oxygen sensor cable from its bracket.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Remove the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Install the oxygen sensor.
  2.  
  3. Clip the oxygen sensor cable back into its bracket.
  4.  
  5. Connect the connector for the oxygen sensor.
  6.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
    NOTE
    The plug connection must be disconnected before the oxygen control sensor is removed. If the plug connection separation point is below the cover for the fuel injectors:



    Remove the lower section of microfilter housing.
     
    Remove the cover from fuel injectors.
     
    Unclip theoxygen control sensor cable from retainer.
     
    Disconnect the plug connection for the oxygen sensor.
     
    Remove the oxygen control sensor.

    Click image to see an enlarged view

    Fig. The removal and installation of the oxygen sensor

     

  2.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Disconnect the connector for the oxygen sensor.

    Click image to see an enlarged view

    Fig. Disconnect the connector for the oxygen sensor

  4.  
  5. Unclip the oxygen sensor cable from its bracket.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Remove the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Install the oxygen sensor.
  2.  
  3. Clip the oxygen sensor cable back into its bracket.
  4.  
  5. Connect the connector for the oxygen sensor.
  6.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Remove the reinforcement plate.
  4.  
  5. Unlock and detach the plug connection.
  6.  
  7. Unclip the control sensor cable.

    Click image to see an enlarged view

    Fig. The location of the plug connection (3) and the sensor cable (1)

  8.  
  9. Remove the sensor.

    Click image to see an enlarged view

    Fig. The location of the sensor (4)

  10.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Replace the sensor, the plug connection and the sensor cable.
  2.  
  3. For the right sensor, to prevent fraying, make sure that the wiring harness is correctly placed on heat shield.

    Click image to see an enlarged view

    Fig. For the right sensor, to prevent fraying, make sure that the wiring harness (1) is correctly placed on heat shield (2)

  4.  
  5. Check stored fault messages.
  6.  
  7. Rectify faults.
  8.  
  9. Clear the fault memory.
  10.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Disconnect the connector for the oxygen sensor.

    Click image to see an enlarged view

    Fig. Disconnect the connector for the oxygen sensor

  4.  
  5. Unclip the oxygen sensor cable from its bracket.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Remove the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Install the oxygen sensor.
  2.  
  3. Clip the oxygen sensor cable back into its bracket.
  4.  
  5. Connect the connector for the oxygen sensor.
  6.  


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Unfasten the nuts that retain the cover.

    Click image to see an enlarged view

    Fig. Unfasten the nuts that retain the cover

  4.  
  5. Disconnect the connector on the sensor.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Removing the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Check stored fault messages.
  2.  
  3. Rectify faults.
  4.  
  5. Clear the fault memory.
  6.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Disconnect the connector for the oxygen sensor.

    Click image to see an enlarged view

    Fig. Disconnect the connector for the oxygen sensor

  4.  
  5. Unclip the oxygen sensor cable from its bracket.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Remove the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Install the oxygen sensor.
  2.  
  3. Clip the oxygen sensor cable back into its bracket.
  4.  
  5. Connect the connector for the oxygen sensor.
  6.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Disconnect the connector for the oxygen sensor.

    Click image to see an enlarged view

    Fig. Disconnect the connector for the oxygen sensor

  4.  
  5. Unclip the oxygen sensor cable from its bracket.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Remove the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Install the oxygen sensor.
  2.  
  3. Clip the oxygen sensor cable back into its bracket.
  4.  
  5. Connect the connector for the oxygen sensor.
  6.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
    NOTE
    The plug connection must be disconnected before the oxygen control sensor is removed. If the plug connection separation point is below the cover for the fuel injectors:



    Remove the lower section of microfilter housing.
     
    Remove the cover from fuel injectors.
     
    Unclip theoxygen control sensor cable from retainer.
     
    Disconnect the plug connection for the oxygen sensor.
     
    Remove the oxygen control sensor.

    Click image to see an enlarged view

    Fig. The removal and installation of the oxygen sensor

     

  2.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Disconnect the connector for the oxygen sensor.

    Click image to see an enlarged view

    Fig. Disconnect the connector for the oxygen sensor

  4.  
  5. Unclip the oxygen sensor cable from its bracket.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Remove the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Install the oxygen sensor.
  2.  
  3. Clip the oxygen sensor cable back into its bracket.
  4.  
  5. Connect the connector for the oxygen sensor.
  6.  


WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
    NOTE
    The plug connection must be disconnected before the oxygen control sensor is removed. If the plug connection separation point is below the cover for the fuel injectors:



    Remove the lower section of microfilter housing.
     
    Remove the cover from fuel injectors.
     
    Unclip theoxygen control sensor cable from retainer.
     
    Disconnect the plug connection for the oxygen sensor.
     
    Remove the oxygen control sensor.

    Click image to see an enlarged view

    Fig. The removal and installation of the oxygen sensor

     

  2.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

2.5L (M52) Engines

WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
    NOTE
    The plug connection must be disconnected before the oxygen control sensor is removed. If the plug connection separation point is below the cover for the fuel injectors:



    Remove the lower section of microfilter housing.
     
    Remove the cover from fuel injectors.
     
    Unclip theoxygen control sensor cable from retainer.
     
    Disconnect the plug connection for the oxygen sensor.
     
    Remove the oxygen control sensor.

    Click image to see an enlarged view

    Fig. The removal and installation of the oxygen sensor

     

  2.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

2.5L (M52TU) Engines

WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
    NOTE
    The plug connection must be disconnected before the oxygen control sensor is removed. If the plug connection separation point is below the cover for the fuel injectors:



    Remove the lower section of microfilter housing.
     
    Remove the cover from fuel injectors.
     
    Unclip theoxygen control sensor cable from retainer.
     
    Disconnect the plug connection for the oxygen sensor.
     
    Remove the oxygen control sensor.

    Click image to see an enlarged view

    Fig. The removal and installation of the oxygen sensor

     

  2.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

2.8L (M52) Engines

WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
  2.  
  3. Disconnect the connector for the oxygen sensor.

    Click image to see an enlarged view

    Fig. Disconnect the connector for the oxygen sensor

  4.  
  5. Unclip the oxygen sensor cable from its bracket.
  6.  
  7. Remove the oxygen sensor.

    Click image to see an enlarged view

    Fig. Remove the oxygen sensor

  8.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

  1. Install the oxygen sensor.
  2.  
  3. Clip the oxygen sensor cable back into its bracket.
  4.  
  5. Connect the connector for the oxygen sensor.
  6.  

3.0L (M54) Engines

WARNING
There is a danger of scalding so only perform this task on an engine that has completely cooled down.


CAUTION
Make sure that the ignition is switched off and no electrical equipment is on or running.

  1. Access the fault memory of control unit of Digital Motor Electronics (DME), check for any stored fault messages, rectify those faults and clear the fault memory.
    NOTE
    The plug connection must be disconnected before the oxygen control sensor is removed. If the plug connection separation point is below the cover for the fuel injectors:



    Remove the lower section of microfilter housing.
     
    Remove the cover from fuel injectors.
     
    Unclip theoxygen control sensor cable from retainer.
     
    Disconnect the plug connection for the oxygen sensor.
     
    Remove the oxygen control sensor.

    Click image to see an enlarged view

    Fig. The removal and installation of the oxygen sensor

     

  2.  

To install:


NOTE
The threads of a new oxygen sensors are already coated with an anti-seize compound. If an oxygen sensor is to be used again, apply a thin and even coat of an anti-seize compound to the thread only.


NOTE
Do not clean the oxygen sensor section which protrudes into the exhaust line and ensure that it avoids all contact with any lubricants.


NOTE
Observe cable routing of the oxygen sensor so it doesn-t interfere with any other system or the exhaust pipes.

 
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