What is an Oxygen Sensor?

Many  people  are  mystified  about  the  workings  of  that device  in  the  exhaust  system  called  the  oxygen  sensor (02S). How  does  something  in  the  exhaust  stream generate voltage  and  help  the  engine  control  module (ECM) to  adjust  the  air/fuel mixture?  What  makes  an 02S go bad?

The  heart  of  a  typical  02S  is  a  thimble-shaped element  made  of  a  special  material  called  zirconium dioxide (ZrO2).  The inner  and  outer  surfaces  of  this element each  have  an  electrode  made  of  a  layer  of thin  porous  platinum. The 02S is designed  so  that the  inner  surface  of  this  element  is  exposed  to ambient  air  (the  atmosphere),  while  the  outer surface,  which  also  has  a  porous  ceramic  coating,  is exposed  to  the  exhaust  gases.

While  some oxygen  is  still  present in burned exhaust gases,  there’s  obviously  more  oxygen  present  in  the atmosphere.  Because  the  oxygen  proportions  differ between  the  inner  and  outer  surfaces  of  the  element, and  thanks  to  the  special  properties  of  the  ZrO2,  a voltage  is  generated  between  the  two  electrodes.

Keeping  in  mind  that  the  amount  of  oxygen  in  the atmosphere  is  relatively  constant,  the  voltage  output will  vary  as  the  amount  of  oxygen  in  the  exhaust gases  varies.  Less  voltage  is  generated  when  the air/fuel  mixture  is  lean  because  of  the  higher  oxygen content  in  the  exhaust.  More  voltage  is  generated when  the  air/fuel  mixture  is  rich  because  of  the  lower oxygen  content  in  the  exhaust.  By  monitoring  this voltage,  the  ECM  knows  how  rich  or  lean  the  air/fuel mixture  is,  and  it  adjusts  the  mixture  accordingly.

Why Do Oxygen Sensors Fail?

So  what  makes  an  02S  stop  working  properly? Carbon  from  exhaust?  Sounds  logical,  but  no,  the number  one  enemy  of  an  02S  is  silicone. When  the  exhaust  side  of  the  element  is  exposed  to silicone,  the  pores  of  the  protective  ceramic  coating
become  clogged.  Once  this  occurs,  the  exhaust  side receives  less  oxygen.  As  a  result,  the  02S  generates more voltage than it normally would for a given air/fuel mixture. his may cause the ECM to lean the mixture enough to cause driveability  problems  or trigger  the  malfunction  indicator  lamp  (MIL).

If the ambient  air  side  of  the  element  is  contaminated with  silicone,  the  porous  electrode  becomes  clogged, reducing  the  oxygen  on  that  side.  Then  the 02S  will generate  less   voltage,  so  the  ECM  tries  to  compensate by  richening  the  mixture. This  too  may  deteriorate driveability  or  trigger  the  MIL.

Sometimes  the  source  of  the  silicone  may  be  the  fuel, but  the  more  likely  sources  are  silicone  sprays, greases,  and  adhesives.  When  you  use  these  products, don’t  let  them  get  into  the  engine’s  air  intake  tract, the  exhaust  system  (upstream  of  the  02S),  or  the vents  on  the  02S.

Contact Us for Towson Auto Repair & Maintenance

For Towson residents in need of top-notch mechanical services, Hollenshade’s is your trusted partner. Our experienced team is here to provide a wide range of automotive solutions, including oxygen sensor repair and replacement. Ensuring that your vehicle’s oxygen sensor functions optimally is essential for maintaining fuel efficiency and reducing harmful emissions. If you require assistance with your oxygen sensor in Baltimore and/or the surrounding region, please don’t hesitate to contact us. Our dedicated professionals are ready to address your needs and keep your vehicle running smoothly. At Hollenshade’s, your satisfaction and your vehicle’s performance are our top priorities.