Thread: Downpipe and O2 Test delete in HP tuners.

Alright I got myself a scangauge II in December and have been watching my KR along with other info. I am typically seeing 3-4 degrees KR climbing hills and in general at the beginning of acceleration. Sometimes I can see as high as 6 but rarely. My thoughts are that by installing a 3" catless zzp downpipe I could eliminate the KR and get better mileage, car has about 120k on it now so I figure the cat might be getting restrictive. I don't plan to mod this car extensively. It is a 2002 gtp. I have been reading that the zzp Rear O2 emulator will not work on 01 and up, they say otherwise but its all over in this forum that it won't work. I also have been reading that HPtuners will not allow you to delete the rear O2 sensor test that dumps fuel. Help with tuning a series 2 L67

My concern is that even if I buy a catted downpipe I may still get a cat code. I would like to delete the cat and avoid the issues in the long run that might be experienced like plugging it up etc. I have access to an older version of HPtuners. Does anybody know for sure if it can be used to delete the rear o2 test and not just the resulting codes?

Or as another option does the bung extender work?

Asking because it seems none has followed up on solving this issue on an 01 up car.

buy a off road 3" dp. then have your stock cat in and out lets opened up to 3 inch, cut and weld the cat in place. now the o2 will work as it should.

The anti-fouler truck works iirc. Also I’ve never done it with HPT but I assume you can set the codes the same way as DHP to get the cat diagnostics to work properly. Also I think the rear O2 sim from ZZP might solve the issue.

its the high flow cat thats causing the issue. the o2 sims work, or find a local to tune that out with dhp.

In order to eliminate cat diagnostics you have to set certain codes to report but not set the MIL iirc. It’s been a few years since I messed with it.

hpt cant turn off the cat test. no matter what your codes are set to.


you can dl old hpt find a bin from dhp then alter its vin# to yours. then kill the cat test with tiny tuner. then load and flash it with the old hpt. Change Vin / Serial Number of Bin File

dhp and hp depository where to find a bin . old hpt tuner software is in the drop box there too.

Scotty is right. Tiny tuner is the only way you can completely disable the cat test. You may get lucky with the bung extender or o2 simulator, but they don't 100% work.

Where does one obtain a tiny tuner these days. I found a download here The Tiny Tuner. I assume I need DHP tuner in combination with tiny tuner. What type of hardware is needed? Seems like DHP is no longer made so do I need to find it used?

used is the only way to go now for a dhp. tiny tuner is on line for down load, it might be in that link i posted with the drop box link too. you want v 1.9. it shows the cat diag stuff.

if it came down to it you could ship me your pcm and i could delete the cat test and make it a canned tune if you wanted for a small fee and shipping back.

that offer stands for you or anyone else looking for a cat test delete.