Do I need to disconnect battery? Is it better to replace both even if only one is bad? MCS got 49k. Any info appreciated.

 

Its never a bad idea to disconnect the battery when doing work on your car. But not a necessity. Also, no need to replace a good sensor, only replace the one that is bad.

 

Then when you are done with yours...come do mine. I kinda tore mine out when I removed my engine..Now my car likes to throw misfire codes and sound like a Subie..

 

I got code P2096 DME O2 Sensor (Bank 1, after cat). is this the one behind? since I only got one new one, can I put the existing front one in the back and put the new one in the front?

 

Why would you want to do that? The back one is easier to get to... I cant remember if the front and back are interchangeable. It tells you which one it is....after the cat (back or aft one).

 

do the back front swap. The reason you'd want to do that is the one behind the cat checks the cat function, the one before the cat is used to set fuel mixture. O2 sensors don't (usually) fail all at once, but rather they gradually poison and the response falls off.

Matt

 

This is exactly the reason why I want to put the used good one from front to back so I can have a fresh one in front where it counts the most. Thanks for the confirmation DO.

 

p2096 is post catalyst fuel trim lean. it probably isn't an o2 sensor failure. i had this same code and it was caused by a leaky exhaust gasket after the cat. it was allowing air to leak into the exhaust right next to the secondary o2 sensor, causing it to incorrectly read a lean mixture. i replaced the gasket and the code went away.

this code is kinda wierd because you can clear it after the repair and it will come right back. you have to drive it for a few days to reset the adaptives, then it will go out by itself.

 

P0138 is the 02 sensor code. My new one should tomm and hopefully my car stops throwing that code.

 

oops, i guess i was replying to purplehaze05mcs's post about his code... sorry.

 

no worries i was just informing purplehaze that p0138 is the most common 02 sensor code and was furthering your statement by areeing that it was probably something farther back than the B1S1or2 02 sensors.

 

Hey, guys. I'm sure this isn't the right place for this post, but somwhat on the topic. Just wondering if old O2 sensors will cause my gas milage to deteriorate? My '02 has 87k on it now and I am getting lowsy milage for some reason!

 

Yep...just replaced mine this weekend. Ive noticed almost a 3-5 mile per gallon gain. The car drives alot better too. I noticed that it idles smoother and accelerates smoother. Yeah the check engine light didnt come on to the very end and i wish it would have come on earlier because i would have replaced it earlier.

 

Thank you pepegrande008! Did you change just the front ones or all of them?