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MDTDan, Toyota Master Diagnostic Tecnician
Category: Toyota
Satisfied Customers: 70
Experience:  21 Years Specializing in diagnosis of difficult to repair concerns. ASE Certified A1-A8 and L1
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2004 toyota camry le: a tune-up..cylinder..oxygen sensors

Customer Question

Hello, I just recently did a tune-up on my 2004 toyota camry le, 4 cylinder, auto. It was recomended that iI also change the oxygen sensors since my car has 117000 miles and these sensors are good for about 100000 miles, my question is, how many oxygen sensors are in this vehicle, which are the types to use (ex. before cat. or after cat) I am confuse, do the oxygen sensors have to replaced ? What do you recomend ?
Submitted: 9 years ago.
Category: Toyota
Expert:  MDTDan replied 9 years ago.


There are two emission systems on this year Camry. The PZEV model has one air fuel ratio sensor and two heated oxygen sensors. The non PZEV has one air fuel ratio sensor and one heated oxygen sensor.

The air fuel ratio sensor is a newer style sensor which operates in place of an oxygen sensor. The AF sensor provides a more accurate measurement and correction of the fuel mixture as the engine runs.

I see no reason to replace the AF or oxygen sensors as a maintenance procedure. The Toyota sensors can be rather pricey and aftermarket sensors can (at times) cause more harm than good. In addition to the expense, the complex on board diagnostic system monitors the performance of these sensors closely and will turn on the check engine light as soon as one of the sensors begins to fail.

If you have concerns whether or not your engine is running as efficiently as possible you could have the long term and short term fuel trims checked with a scantool. Anything below 10% correction is considered a well running engine. A positive long term fuel trim over 10% may indicate a dirty mass air flow sensor. This is a more likely cause of poor fuel mileage and or performance. The MAF sensor can be cleaned with brake or electrical contact cleaner to restore its accuracy.

Let me know if I can further assist you with your question.


MDTDan, Toyota Master Diagnostic Tecnician
Category: Toyota
Satisfied Customers: 70
Experience: 21 Years Specializing in diagnosis of difficult to repair concerns. ASE Certified A1-A8 and L1
MDTDan and 3 other Toyota Specialists are ready to help you
Customer: replied 9 years ago.
Relist: I still need help.
Expert:  MDTDan replied 9 years ago.

Hello again,

Can I clarify my answer or assist you in any way? Are you looking for a second opinion?

I'll be glad to help further.


Expert:  Ted Ritter replied 9 years ago.
Unless the check engine light came on indicating that there is a problem with the O2 sensors I don't see a reason to replace them, they are not a maintenance item and there is no recommended replacement interval, although Camrys do have frequent problems with air flow ratio sensors and O2 sensors, they are normally not replaced as a preventive measure but rather when they have a failure. As far as I know there are two sensors, one in front of the cat converter, this is an air fuel ratio sensor and one behind the cat which is an oxygen sensor, it's function is to check the oxygen content after the cat which will indicate whether the converter is working properly.

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