So I’ve got a 2001 Trans Am, been throwing O2 codes for a while. Got all the Denso replacements, got the fronts done no problem. The old ones have been on the car a long time, at least 15 years. It’s a Midwest car. Needless to say, I cannot get the rears out. They are totally corroded and rusted on.

I’ve soaked them like 6x with PB Blaster, tried driving the car and getting them out warm, propane torch, beating the **** out of them, breaker bar, nothing works.

Car has LTs and no cats, do I even need the rears? Car was tuned by the previous owner, and it runs great so I want to keep it the same as much as possible to not have to retune.

Can I delete the rear O2s without having to re tune? What do I need to do that? Honestly I kinda want to delete one and put a wideband in the spot for the other if I can. Any help appreciated. Thanks.

 

Their is a socket adapter you can get for air hammers that lets you use a wrench to turn a socket while simultaneously beating the **** out of rusted parts. You would have to cut the wires off the old sensors to get a socket on, but it is usually a pretty good last resort for situations just like you have.

 

Not having rear O2 sensors would likely throw a Check Engine Light so yes, a minor tuning change to eliminate that code would probably be required.

Rick

 

If you don’t have cats then you don’t need them. Just get o2 simulators. I’ve been using them for 20 years on my Camaro. Then you can just Leave the bad sensors installed.

 

Exactly this.

No need for the sensors at all, they do nothing besides monitor cat operation. But you don't have cats, so...useless.

Not even sure that you would need O2 simulators. I'm sure the rear O2s were already turned off in the tune, otherwise you would have been getting codes for them for as long as you've owned it (because you don't have cats, so their readings would have always been outside the threshold).

The current bung threads might be destroyed upon removal of the sensor (if it's *that* rusted into place), so if you want a port for a wideband you might need to weld a new bung in place regardless.

 

If the tune was done right they would have been turned off, I'm wondering why they are still on the car in the first place if it has LT's and no Cats.

 

My dad got the car around 08 and rarely drove it for 10 or so years, I got it about 2 years ago. He hadn’t really changed anything ever, so the previous owner for some reason put the rears back in after doing the headers and exhaust. It definitely has a tune, but I assume they are not turned off, because then why would he even put them back? It never made much sense to me. It has been throwing o2 codes, but I read headers can do that so I’ve just been re setting the check engine light with my scanner.

It was missing really bad, I was kinda chasing problems and throwing parts at it. It’s got 180k, so I figured some new sensors wouldn’t hurt anything, and since it was always throwing the codes maybe they were actually bad. The miss turned out to be a burned plug wire, got a new set of wires and cleared that right up.

 

If it's not throwing any catalyst related codes, then they have already been tuned out. It would not be possible to have no cats, functional rear O2s in place, but no cat-related codes without custom tuning or simulators/anti-foulers/some other sort of defeat device. If that were possible, then nobody would ever need custom tuning to pass an E-check after a cat delete.

 

^^^^THIS. I think it bears repeating that the ONLY purpose of the 2nd O2 sensors is to verify the cats' effectiveness/efficiency. THAT IS IT!
If cats are deleted these sensors serve no purpose and should be deleted when the cats are deleted.

 

So I replaced the front two O2s with the denso sensors. Since I couldn’t get the rears out, and I figured they weren’t even reading because of the tune, I just left the old ones in. Reset the check engine light, and took it for a drive.

It was missing pretty bad with the old plug wire that was burned through, that seems to be all fixed with the new wires. But even though I replaced both front O2s, and reset the CEL, it still came back on after about 50 miles. P1133 and P1153. Looks like that means it’s running lean. Any ideas?

 

It would be interesting to know your values for Long and Short Term Fuel Trims for each side of your engine. Have you checked for an intake manifold vacuum leak that lets in extra, unmetered air that causes your fuel mixture to shift lean? Your MAF sensor could also be dirty.

Can you attach a log of your OBD2 parameter data with the engine running in closed loop, please?

Rick

 

I have not checked for a leak, but I did clean the MAF about 2k miles ago.

 

Dirty injectors will do this. Try a bottle of injector cleaner if your cheap, or better yet pull them and have them professionally cleaned.

 

Does anyone know of a good place that can break down the codes? I never use the scanner and I have no idea what it all means

 

If you are referring to the abbreviations, google works just fine. However, you will come up with a lot of irrelevant nonsense if you just use some of the terms by themselves. For instance IAT means intake air temperature, but if you want a relevant search result, add car at the end. IAT car will tell you what you want to know, while just IAT will bring up useless crap.

 

Ok guys, based on recommendations here I got some Chevron with Techron, ran that through. Super concentrated. Full bottle to about 1/2 a tank. Ran it through, refilled the tank, and changed the oil. I’m in Michigan, I always use 93, and the car gets Mobil 1 filters and Pennzoil 5-30.

Light went out for about 150 miles, but came back on while cruising. Every time the light comes on, I’m not beating on the car at all.

To summarize, new plugs, new wires, new fuel filter, new oil, new front O2s, fresh tank of Chevron, did it again. No cats on car, rear O2s stuck in, everyone seems to think they should be deactivated cuz the car is tuned, but….









Want to add car runs good, idles good, and pulls hard with quick throttle response. 180k miles.

 

That scanner has the ability to graph sensors, so you need to graph both B1S1 and B2S1 and see what the pattern is. Watching the numbers jump around won't help you any. Go into live data (LD) and scroll down until you have highlighted O2S B1S1 ( and then O2S B2S1 ) and click the arrow to graph. My guess is that your sensor cross counts aren't sufficient and that your voltages are going to hover around the higher ranges, indicating a rich condition. Nothing is wrong with the sensors, most likely, it's probably a fuel system issue. You should put a fuel pressure gauge on your fuel rail and monitor fuel pressure both running and after shut off. If your fuel pressure drops quickly after shut off, you may have a leaking fuel injector.

I drive up to Alpena fairly often, and my route takes me close to Houghton Lake. If you can't get this figured out, I may be able to help out. The weather is about to turn, though - you store your car during the winter? I won't be up again until around Thanksgiving.

 

If you have NO converters, you need NO rear O2 sensors.
Their sole purpose is to report converter efficiency, and nothing else.
They have NOTHING to do with the tune whatsoever

 

For the purposes of this thread you are correct. However, most tuning software does not allow you to disable a background test of the rear o2 sensors. This means that for people who are fine tuning their fueling, there will be what appears to be an unexplained "glitch" in their numbers that comes and goes, even with the rear o2's disabled and removed. This has no practical effect on anything, but it has confused several new tuners.

 

Have you checked fuel pressure? If it is that could be causing your issue.