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

Originally Posted by Sabrewings

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.

HP Tuners calls these check boxes "SES Enable". TunerCat OBD-2 Tuner refers to them as "DTC Enable" (which sounds like the same thing DHP refers to them as).

The problem is I don't think anybody has the definition for these check boxes entirely correct. In factory stock cal's I have seen these boxes NOT checked for trouble codes that do turn the check engine light on. I do know in the 05 Monte SS cal I tuned, even when setting the DTC to "No MIL"; leaving this box checked resulted in the Driver Message Center lighting up with a warning message stating the vehicle needed to be serviced as soon as the code set (after the cat diagnostic had run). I had to uncheck these boxes next to these CAT and post-CAT O2 sensors codes to prevent the Driver Message Center from displaying these warnings.

So I should be alright with 98 PCM and no rear 02 sensor?

I'm getting the exhaust done tomorrow morning, and wondering whether to have a rear 02 bung and sensor installed or not...

advantages/disadvantages?

Originally Posted by tylerbinski

So I should be alright with 98 PCM and no rear 02 sensor?

I'm getting the exhaust done tomorrow morning, and wondering whether to have a rear 02 bung and sensor installed or not...

advantages/disadvantages?

98 PCM running 98 programming you should have no problems with a missing rear O2 sensor. BUT, you might want to install a rear O2 bung for a wideband down the road just in case.

it wont throw a code but when your cruising the car will at random max out the fuel trims making you run pig rich in an attempt to see if the rear O2 will respond to the changes in AFR.

So if i want to run a race pipe that came with my speed daddy headers i just need to have an o2 sensor plugged into it even though there is no CAT. As long as the engine can read the o2 it wont keep running the diagnostic? Then just set the DTC's to no reporting? And everything should run a ok?

Originally Posted by apierce1289

So if i want to run a race pipe that came with my speed daddy headers i just need to have an o2 sensor plugged into it even though there is no CAT. As long as the engine can read the o2 it wont keep running the diagnostic? Then just set the DTC's to no reporting? And everything should run a ok?

That's a good question. I don't know what would happen if you got rid of the cat and left the rear O2 in there. The Monte I tuned on didn't have a rear O2 or a cat so I never got to try it.

I would say go ahead and try disabling the catalyst codes only (leave the post-O2 codes enabled) and then watch your fuel trims as you drive and see if it tries to run the cat diagnostic. It may try to run it but should soon quit running it as the rear O2 would show rich immediately as the test begins.

Give it a try and let us know what happens.

-ryan

Originally Posted by apierce1289

So if i do what you guys just suggested the car will only run the diagnostic once and should stop then my engine should remain running normal. The computer will just think it has a bad CAT and it wont effect the way the engine runs? Oh and also i don't have the software i am just doing a **** load of research to find a solution to this issue. Will the above SES code try to run more than once? So that me and everyone else will know what to do

Assuming you are going to leave the rear O2 installed and the codes for it enabled (as they are stock); if you set the Cat Diagnostic DTC(s) to "No MIL", the test will run 1 time, set the Cat DTC, and then future tests will not run.

If you disable the Cat diagnostic codes completely, the PCM may attempt to run and re-run the tests, but I would THINK it should immediately discontinue each test as soon as it sees that rear O2 sensor go rich. I do NOT know if it will keep trying to run the test of if it will discontinue running tests for that key cycle because I never had the chance to try it.

Originally Posted by FoSHO99

In tinytuner, go to diagnostics> cat diagnostics? and there are 2 tests to set to disable, I'm not at the program right now for specifics but I know they will disable the tests.

.

What version of TinyTuner are you using? I have v3 and it isn't showing any cat diagnostics to disable at all...

I was planning on getting a ZZP pcm, do they set the codes to no reporting or do they completely remove them? I would like to have the computer know it has a bad CAT but just not show up in emissions check so I pass that way it wont keep running it since it will think its bad. Also can someone hook me up with Overkillwill's contact info cause I'd rather pay him to get the actual diagnostic test completely removed so it will never do that test again.

Originally Posted by apierce1289

I was planning on getting a ZZP pcm, do they set the codes to no reporting or do they completely remove them? I would like to have the computer know it has a bad CAT but just not show up in emissions check so I pass that way it wont keep running it since it will think its bad. Also can someone hook me up with Overkillwill's contact info cause I'd rather pay him to get the actual diagnostic test completely removed so it will never do that test again.

How does the emissions testing stations in your area conduct their tests? Do they hook up their scan tools to check to see if the PCM reports a certain diagnostic test has run or not? If so, then just disabling the code will result in these tests always showing "NOT RUN" on the scan; and disabling the diagnostic may result in the same thing being displayed.

I'm not sure what Overkillwill does, but you had better check to make sure whatever he does to disable the diagnotic test from running will report that diagnostic test result on the scan has "RUN AND PASSED"; otherwise you'll probably fail the inspection (that is if the smog guys are looking at this data).