There are two pairs of sensors 1) "upstream" -> before the catalytic converters, and 2) "downstream" -> after the cats.

The upstream 02's primary function is to monitor the fuel air ratio for the engines fueling.

The downstream 02's primary function is to make sure the catalytic converters are doing their job by monitoring the exhaust emissions.

Normally when one of the four goes bad, a code is thrown that will tell you exactly which sensor needs to be replaced. "Bank 1 Sensor 2" - Something like that.

(Sensor 1 being upstream, Sensor 2 being downstream).


They are quite easy to change -- provided that they come out of the exhaust without taking or leaving threads! Sometimes they get really rusted in there. Since the dealer already broke them free, they should be good to go as far as that is concerned.

 

Hmmm... okay, just found out they replaced the two upstream only... for $160, not sure what kind they used.. but I did see the Bosch for about 30 or 40 bucks.. wondering if I should let them take theirs back and save about $80, or just let em ride

 

Just curious why they were replaced? Did two of them fail? O2 sensors aren't something you normally replace until they fail (and the computer will tell you when they fail, and which one, by throwing a code). Mine have 115,000 miles on them.

 

Yeah, it threw up the P0420 code I believe it was.. they said they would replace the o2 sensors first and see if it comes back on.. then replace the catalytic converter

 

Okay, so the BIG question is.... Do I keep what the dealer gave me and pay $160... Or do I have them take em out, and get my own upstream O2 Sensors and do it myself??? Also how hard is it to change them? Any info would be greatly appreciated

 

Is there a warranty on the dealers sensors? If so i would give them the $160 and call it a day. Chances are those sensors will last a good long while. Also, if you make them pull em and eat em, they wont be happy. And you might want to be in their good favor in the future.

Or if you've got the balls, you could buy the $30 sensors, swap em yourself before returning to the dealer... then put the $160 dollar sensors back in when you get home. Hahaha Stealership!

 

There real easy to change they make a special socket that's notched out on one side. Do it when the engine is cold go to auto zone and have them hook it to the computer and see what bank it is a Bosch is about 20-30 and the two lowers are the same the two upper are different the plug will have the same clips as the doors and make sure you use the anti-seize provided

 

That is a pretty good idea lol... kinda risky though..

 

Good info.. thanks

 

Just to clarify, upstream is before the cat, right?