I have a 92 Camry and was surprised to find that it did not have a heated 02 sensor and nor did it have a second 02 sensor after the cat. Did the 93-96 use any heated 02 sensors and was there a sub-oxygen sensor after the cat?

 

My camry is a 93 and I don't believe it has a heated oxygen sensor. As far as that goes I believe the heated o2's started being used in 95 or 96 when the computer systems in all u.s. cars switched to OBD2 which is known for having the check engine light that will come usually for emission related problems.

As far as having a second o2 after the catalytic converter. That is typically something that you'll find on California emissions vehicles. Basically any car made to pass Californials more strict emissions requirements will have different and more parts like that to make it run even cleaner than the rest of the country.

The weird thing is about half of the cars I look at have California emissions. A lot of the car companies are making their vehicles super efficient and super clean running just to help the enviornment and therefor those cars will be clean enough to be registered in california so the emissions will be California emission (o2's before and after the catalytic converter) as opposed to Federal emissions. Hope this answered your questions.

 

Heated O2's and post cat O2's came in with OBDII regs. It's not just a California thing. The purpose of the heated O2 is to get the car into closed loop faster. Purpose of the post cat is to monitor cat efficiency. Without the post cat sensor, the engine could put out rich mixtures and burn out the cat.

 

If you read my previous post carefully you'd see that I said the o2 sensor after the cat is a California emissions thing and that the heated o2 was an obd2 thing.

As far as most cars having post cat o2's. Most if not all federal emissions vehicles will not have them. The sensor in front of the catalytic converter is enough to keep the mixture safe enough for the catalytic converter. California emissions require the post cat o2 so that if the cat stops functioning as it is supposed to you will be let known by a dtc setting and the check engine light coming on. No other state requires this therefor if its Federal emissions equiped it will not have that post cat o2.

 

My OBDI 95 has a pre and post cat O2 sensor. There is no separate spec for California. I don't know if it is heated or not butthe FSM test for the main O2 sensor says to warm engine to operating temp then warm thesensor by holding 2500rpm for 90 seconds. Thatsounds like a non-heated sensor.FSM also says only test post catsensor when code 27 lights the CEL. Code 27 test uses a2 trip logic test. Apparently code 27willNOT show on CEL light with first part of trip test but will show on 2nd trip test if there is a problem with the sensor.

 

I'm sure theres exceptions to everything. the easy way to tell if the sensor is heated is to see if it's a 4 or 5 wire sensor its most definately heated. Also are you absolutely sure your car isn't california emissions? more than 1/2 of the vehicles out in the u.s. are designed that way now just so they can be as clean as possible. On the catalyst information which is usually stuck to the under side of the hood it will say "this vehicle conforms to us emissions blah blah blah and to california..." IF it is. You probably already know this and if so don't take it the wrong way that I'm typing this. Other people read these to like the original poster

 

can a "lay person"change a oxygen sensor and is there something in detail on line that will walk me thru it

 

I got code 21 and 26 from my 93 camry. Code 26 says #2 O2 sensor. Which manifold, (front or rear) is #2 mounted on? Logic would indicate front is 1 and rear is 2 but number 1 cylinder is on rear bank so my logic may not apply here.