The second o2 sensor has to go after the cat otherwise its pointless to even install it. The ONLY thing that second o2 sensor is for is it moniters the efficiancy of the cat by verifying the reading of that 02 sensor is cleaner than the one off the header verifying the cat is doing its job. It has no application for the engine at all.

 

Thanks, I was just making sure because im not a mechanic, just a home DIY'er lol.

 

22mm wrench to remove either,,if you have gutted cat or test pipe you will have to do the trick of using a set of spark plug anti fowlers ,one drilled out to allow the o2 to screw in it the second goes on thefirst and then reinstall the o2 this is for the second o2 only it makes it read-----^-----^------^ like it should with a functioning cat. the universal o2's work great .my primary got crappy after running vp blue at the track for several weekends.

 

You're supposed to install the O2 Sensor AFTER the cat. The one right before the cat is for a wideband sensor.

As I said above, the sensor is supposed to be after the cat.

The reason for the second sensor is to verify the cat is doing it's job. The first sensor reads the ERG, the second sensor reads the ERG, and then the ECU compares the two readings. If they are not significantly different it knows the cat is NOT doing it's job. Therefor if you put the second O2 sensor before the cat, the readings would be nearly identical.

 

You can get the oem versions at advanced auto for around $80, $160 for the second I believe. At CAP the oem version of the first one was $120 for me. You can go with the universals, but they have shorter wiring so you have to cut and splice a good amount from your existing wiring and connector. Always use heat-shrink connectors for anything outside the car.

Never get **** from the dealer unless you absolutely have to. I'm still a little irritated that they have the nerve to charge $350 for a timing belt change, and the only extra thing they do is "inspect the condition" of everything else. You'd think they'd replace all your belts, tensioners, and pulleys for that amount!

22MM wrench or 7/8 will work, or an adjustable. You might not be able to get them off without heating them up with a torch, depending on whether they are original or aftermarket, and if anyone put anti-seize lubricant on the threading. DEFINITELY buy a $2 packet of this when you pick them up, saves you tons of headaches taking them off in the future.

 

Ok, so unforunately the weather is against me for the next few weeks so I can't get under the car to inspect wtf is going on. All i know is there is one o2 sensor currently in the stock exhaust mani, and then one "wideband?" o2 sensor before the cat, and NOTHING after the cat. So what do I do when i install my new exhaust system.

 

Listen, I do NOT have a stock exhaust, what im looking at under my car is one o2 sensor on the downpipe BEFORE the cat and nothing after it. Im worried about how to make everything work once I have replaced all the parts. Does that mean I should plug the o2 sensor hole in the new downpipe and place the o2 sensor in the plug after the cat? Currently my exhaust is welded crap and there is no option for a o2 sensor after the cat, no "bung" i guess. ?correct me?

 

I o2 bung in the downpipe is usually for a wideband o2 sensor. You should have 2 stock sensors, one in your stock manifold (unless thats gone too) and the other right after the cat. After you install the new part you should have one somewhere before the cat and another right after the cat

 

I just found this after scouring the service manual, this is pretty much exactly what my setup looks like now, so i am pretty set on keeping it the same, the car ran good til the front o2 sensor went bad and then the cat shortly after(which was only 3 months old).