4Sforlife

Hello all I’m in need of some knowledge help from someone with a 997.2 4s or similar. So for starters I purchased my 4s over a year ago and have modified it to the best of my ability without doing any internals. So the car is a 09 manual with a computer flash,gundo hack, sharkwerk center pipe, intake plenum and a exhaust header with high flow street cat from a manufacturer that I won’t mention because they have been fantastic in trying to remedy a solution. The problem I’m having is with the header. The minute the street header was placed I’m starting to have a pending code P0431 which is warm up cat efficiency below threshold. I’ve tried everything possible including changing all o2 sensors, changing exhaust gaskets from exhaust manifold to the CAT. Also I’ve flashed the stock program back onto the car. I’ve follow the manufacturer driving to set monitors for IM readiness. But my problem is I can’t get the car to pass emission. The code PO431 is only pending and not stored or permanent so I’m not sure if that’s the reason why the monitors are not running for CAT or EGR. I’ve also tried a spacer on bank 2 sensor 2 and it converted that code from pending to stored. Also I have only the EGR and CAT incomplete after driving hundred if not thousands of miles. If anyone has had this problem before please please help!!!! I’m beyond frustrated at this point. Please comment if can provide some positive input. When I look up PO431 it is caused from bad CAT, Bad O2 sensors, or exhaust leak.

8x57IRS

As an idea: Do you have the possibility to check the secondary air pump? The pump blows fresh air behind the exhaust valves and provides afterburning in the exhaust gas in the start phase (only a few minutes). This accelerates the heating temperature of the catalytic converters. In case of a malfunction the heating gradient is lower and this error message can occur.

Petza914

We've seen this problem with certain hi-flow cats. If you're using 100 cell and not 200 cell, you're likely out of luck. No issues at all with CELs.usinf my Fabspeed 200 cell cats. Multiple people have had issues with the Top Gear cats and codes. A little tough to help since you're not naming the supplier as we may or may not be familiar with issues others have had with them.

4Sforlife

I am using a 200 cel from a reputable manufacturer.

4Sforlife

And the code is only pending not stored. Not top gear CAT.

4Sforlife

will check but would this cause it to be unilateral??? Problem is only showing pending code on bank 2.

4Sforlife

just read 997.2 does not have secondary air pump uses something else.

fireman

So you modified the emission control system. In a state where they test. How about putting the stock equipment back in?

8x57IRS

Do they have a 997-reference to prove that their density is working properly?

Sorry for the misinformation, did not read carefully enough

jdubdds24

Had this same problem, put in some of the fabspeed style O2 spacers, drove the car for 30m, shut it off, cleared codes, turned car back on and the issue went away. There are lots of combinations you may have to go through before it works, O2 sensors can be very fickle, sometimes the spacers are too short, others too long, others too restrictive others not restrictive enough. Aside from trying multiple spacers, may make sense to put factory equipment back on then get the inspection and swap it back. I do all my own exhaust work and it really isnt bad at all, if you're paying someone to do that then well...pay to play i suppose. Good luck!

4Sforlife

modification isn’t the problem otherwise code would be on both bank. It’s only a pending on bank 2. And stock returning stock is NOT an option.

4Sforlife

with spacers I attempted with a straight and it passed the IM readiness but immediately threw a code. But I’m curious do I need spacers on both pre and post CAT or just post?

jdubdds24

post Cat Only.

Here’s mine.

4Sforlife

tried that and the pending code became stored. Popped up inside car.

ADias

Most specialists say that PAG does not leave a lot of unused performance on the table So the question is, is it worth modifying these cars? What are the gains? Are those gains meaningful? Are those gains significant on the track? Are those gains, if any, sensed by the butt-dyno on the street?

Not to enter into the legal issue of changing emission parameters on a car driven on the street...