For you running catless downpipes with hp tuners
09-05-2008, 10:02 PM
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For you running catless downpipes with hp tuners I have a catless 3in. downpipe on my 07 MCSS. I also have HP Tuners in which I used to turn off the service engine light. I disabled any O2 codes that were bank 1 sensor 2 codes and po420 low eff. I also disabled the CAT over temp protection test and cat test with hp tuners. My gas mileage dropped ever since I added the catless downpipe and this tune. Well, the other day I noticed my car wasn't switching to 4 cyl mode. I didn't disable DoD or change any settings. Tonite I enabled the 2 cat tests and low and behold now I have 4 cyl. mode and the car is a lot more responsive. Seems to have leaned it out somewhat also. Which is great, it was running way rich. Just something interesting I found out. Figured I'd share with you guys.
09-05-2008, 10:10 PM
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yeah, DoD won't function with a SEL, also sounds like you were in some sort of limp-home mode with the rich fueling. Good deal on getting it sorted out. Your remote starter probably works again too.
09-05-2008, 10:20 PM
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I didn't have an SEL on. But all possible O2 codes and cat eff. code were disabled. I just thought its weird that the cat over temp protect and catalyst test aid DoD apparently. When you disable these tests, you disable DoD. I was still getting damn near 19.5-20mpg in a rich v8 mode all the time. I just can't believe I've been running my car like this for 2 months and now just noticed 4cyl mode wasn't engaging. Can't wait to see what my gas mileage is now! 
09-06-2008, 01:18 AM
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I pulled my 3inch pipe a some time ago. Granted I never had a tune but going back to the stocker the car felt way better. I'm thinking these 3inch downpipes are too big. Maybe if the engine were more radicle and larger it would accept it better...
09-06-2008, 12:02 PM
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My bad.
