Removing rear O2 sensor on 01-newer PCMs -- Things you should know

I need a solution for this also... I have a powrtuner and 3 cars that are 01+, 2 surge at idle right now and my ltft's are inconsistent.

same problem here, hope someone can figure this out! myself and DanGTP are trying to tune my 05 GP with a catless DP using HPTuner and the LTFTs are way up there. Getting a lotta KR in the mid range RPMs too...i guess asking OverkillWill how he overcame this issue would defeat his purpose of selling custom-tuned PCMs?

I have a 2001 with no cat or rear o2 sensor. My ltft's seem to be pretty close to 0 and my wideband fluctuates around 14.5 - 15. I guess I'm a lucky one?

I guess I'll add my 2 cents here. Haven't been here in awhile.

The O2 sim does fix this on 01+ cars, the pcm is only looking for normal switching from the sensor. You can also just run the sensor and eliminate the mil in the pcm. I've got numerous cars running like this here in the twin cities.

Another option in simply running 00 code in a 01/02 car. This seems to only work on GP's though. The bcm's in regals/impalas/montes/bonnies don't like when you swap pcm code to diff years, even with security parameters modified. You can however swap to a 2000 bcm in your car and rock the 00 pcm code, done this on a few car's too.

you 03+ guys can't do this due to issues in the trans/ different pcm for 04+ guys.

If anyone has anymore questions I'll gladly try and answer.

-Chris

When you say run the sensor do you me just run it in the pipe with no cat?

yes. then just make it so the check engine light doesn't come on.

I just installed my 02 Sim and it worked no more ses light. I will scan my car tomorrow to see if it is still running rich. I would assume it is not because i no longer have the code front 02 insufficient switching from running rich all the time.

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Originally Posted by 01GTP

I just installed my 02 Sim and it worked no more ses light. I will scan my car tomorrow to see if it is still running rich. I would assume it is not because i no longer have the code front 02 insufficient switching from running rich all the time.

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The insufficent switching DTC is not caused by these diagnostic tests running. It will only set if the PCM does not see an O2 sensor hooked up and working. These diagnostic tests that the PCM runs causes the engine to run rich and lock fuel trims to max positive amounts UNTIL the PCM sees the expected return signal from the Post-Cat O2 sensor (signal = high voltage). BUT once a Post-Cat O2 sensor DTC sets, all of these diag. tests will cease running.

Dave @ TripleEdge reported earlier that an O2 sim DID NOT fix this issue for him. If it works for you, great. Just make sure you watch the scanner readings and make sure your fuel trims are not locking full rich while driving (and at the same time the pre-cat O2 sensor is outputting high voltage - above 0.750v). If this is happening, your PCM is running these diag. tests and you will need to take action to correct them.

I hav a 98 gp gtp with 3.4 pully a cai, flowmasters and jus added headers and had the converter removed ... could i run a chance of havin this problem? Or does this only happen on 01+ cars? I havent tuned for the headers yet and the check engine lights on bc of the cat i knw and im waitin for the o2 sensor extender wire bc of the headers so im actually not runnin any o2's at all ... I took the car dwn the track and i ran 14.2 @ 97 yea i knw not smart but was jus curious .. By gettin a tune and the o2 plugged back in is there a chance of 13's? my best without the headers was 14.0 @ 96 mph

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Originally Posted by shawn

I hav a 98 gp gtp with 3.4 pully a cai, flowmasters and jus added headers and had the converter removed ... could i run a chance of havin this problem? Or does this only happen on 01+ cars? I havent tuned for the headers yet and the check engine lights on bc of the cat i knw and im waitin for the o2 sensor extender wire bc of the headers so im actually not runnin any o2's at all ... I took the car dwn the track and i ran 14.2 @ 97 yea i knw not smart but was jus curious .. By gettin a tune and the o2 plugged back in is there a chance of 13's? my best without the headers was 14.0 @ 96 mph

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That sounds really stupid and I dont think i've heard anybody driving their car around with no 02 sensors and absolutely never heard anyone racing at the track with no 02 sensors. You should be able to just delete the codes for the bank 2 sensor or get a 02 sim. Shouldn't have a problem with this 01+ crap.

Well, along with what DOHCZ34 said, I think I am going to try and get a stock 2000 .bin file for my powrtuner and import everything i can from my current 01 tune and go from there. I have a 02 sim. installed but I think it crapped out on me because the codes are coming back up and im getting horrible gas mileage, the 02 sim. still flashes like its working.

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Originally Posted by FoSHO99

Well, along with what DOHCZ34 said, I think I am going to try and get a stock 2000 .bin file for my powrtuner and import everything i can from my current 01 tune and go from there. I have a 02 sim. installed but I think it crapped out on me because the codes are coming back up and im getting horrible gas mileage, the 02 sim. still flashes like its working.

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I think other people have tried the O2 sim before and it didn't fix this issue either.

I have an 01 gtp with a 3" catless down pipe and a zzp 1.0 pcm, and i think i might have this problem. It does seem to run a little fat, it has been this way for a bout a year. Is this something to worry about, what is the worst thing that could happen?

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Originally Posted by specialeditiongtp

I have an 01 gtp with a 3" catless down pipe and a zzp 1.0 pcm, and i think i might have this problem. It does seem to run a little fat, it has been this way for a bout a year. Is this something to worry about, what is the worst thing that could happen?

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The worst thing that could happen is the engine running too rich a lot of the time which COULD result in what's known as "cylinder wash-down" of gasoline. Basically the cylinders will glaze up causing excessive blow-by and you will end up with a lot of gasoline making it into your oil which COULD result in eventual engine bearing failure.

Of course this is the worse-case-scenario and it may never happen to your car. Depends on a lot of factors. Best thing you can do is hook up a scan tool or other scanning device and watch your fuel trims and front O2 sensor voltage readings. If your PCM is locking the fuel trims high in the +'s and this results in the O2 voltage locking high (above 0.750 volts or so) for extended periods (more than 20 seconds) while driving, then you probably have the problem described in this thread and need to take action to prevent potential issues down the road.

Just cause I haven't been in this thread in a while, I don't have this problem, with my 2001, or 2002 bin file, one is a GT, and one is a GTP bin.....but when I do plug in my EVAP, I get a -20 or more LTFT...... damn emissions throwing off my LTFTs

I scanned my car last night, my ltft stayed a 0 the whole time, and my stft moved between -2 and +2, and my o2 sensor seemed to be reading very well. So I quess im in pretty good shape.:th_thumbsup-wink:

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Originally Posted by 02BlueGT

Just cause I haven't been in this thread in a while, I don't have this problem, with my 2001, or 2002 bin file, one is a GT, and one is a GTP bin.....but when I do plug in my EVAP, I get a -20 or more LTFT...... damn emissions throwing off my LTFTs

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I didn't have the problem before the top swap. Now that I'm running L67 code I'm having it. Gonna set the rear O2 codes to no MIL and just deal.

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Originally Posted by Sabrewings

I didn't have the problem before the top swap. Now that I'm running L67 code I'm having it. Gonna set the rear O2 codes to no MIL and just deal.

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Don't forget to uncheck the "SES Enable" box on all CAT and Rear O2 diagnostic codes you set to "No MIL". If you don't do this, and you have a Driver Message Center, it may light up with a "service vehicle soon" message.

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Originally Posted by Sinister Performance

Don't forget to uncheck the "SES Enable" box on all CAT and Rear O2 diagnostic codes you set to "No MIL". If you don't do this, and you have a Driver Message Center, it may light up with a "service vehicle soon" message.

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Not sure what tuner you're using, but the DHP PT does it differently. I can set the codes to enable or disabled, and if enabled I can set what type (MIL or no MIL) and how many trips to set the code and how many trips to make it go away.

i have an 01 gt.. am i gunna have to worry about this with the overkill pcm I just got?