Joec500

My car is due for SMOG and in CA they check for flashes, so I flashed my ecu back to stock and went through the drive cycle to set readiness, but my car is now getting cat efficiency codes P0431 and P0421 for bank 1 and 2 post cat o2 sensors. I am curious if anyone has experienced headers with 200 cel HJS cats throwing CEL's.

I ordered some o2 sensor spacers to give that a try, but I was a bit disappointed as I paid the extra money so I wouldn't have to deal with this at SMOG check time.

I wonder if these HJS cats just wear out a lot faster than the OEM ones? For the record when I first had these headers they didn't throw a code, this was about 1 year and 9,000 miles earlier. I bought these second hand not sure how many miles the previous owner had.

Curious if anyone else has seen this?

Cuda911

I installed a full Fabspeed exhaust system on my 996, including those same cats. Threw CELs all the time. Fabspeed had assured me that there would be no CEL issues before I bought the parts. O2 sensor spacers didn't help.

Eventually I sold the car. Could never resolve the CEL issue, and Fabspeed was no help at all. In fact, Joe F. was downright nasty when I tried to discuss the issue with them. Not a fan of Fabspeed at all.

AdamSanta85

No issues with my car

Joec500

Did your Tune modify the secondary o2's so it didn't throw a code. I know my tune maniplutes something to make sure I don't throw a code. It's lame that CA recently checks for ECU tunes or else I would have zero issues

Chimcu

Had the same issue with mine 997.1 xpipes.. couldn't find a solution.. never giong fabspeed again

AdamSanta85

No, I had no codes running just headers. To best of my knowledge my tune doesnt disable the rear sensors.

Have you done a mechanical inspection? No leaks, sensor wires look ok?

thesaintusa

I would verify that the tune doesn't disable the sensors.

Many (not all) tuners will disable the codes if they know you have HFCs to avoid this issue.

I know of people who have been in this situation unknowingly.

desmotesta

I have Soul Sport headers with 200 Cel cats and O2 Spacers, in spite of that I have had a couple of instances of P014A and P013E along with CEL.
They codes as well as the Check Engine light goes away on its own.

Thankfully no P0431 or P0421 but I did get those with Soul Catless Headers (With O2 Spacers) on my Cayman 987.1S and accepted them as part of the deal (catless headers)

AdamSanta85

I ran the headers for thousands of miles before I got a tune, no CEL.

desmotesta

strangely enough, this is pretty typical. As in different people having different results,

I purchased my Soul Sport headers preowned and the previous owner sold because he was having issues with CEL pretty frequently. I have been fine on the same set with the same set of O2 spacers.

Go figure

AdamSanta85

@Joec500 How long after resetting the CEL, does it take to come back? Are your sensors original? Think it could be a combo of worn sensors plus high-flow cats?

AdamSanta85

https://rennlist.com/forums/991/1256...spacers-3.html

Seems like the J style O2 spacers worked for these guys

desmotesta

Yup, thats what I have. They are a pain to install but worth it. Only codes I have had are "delayed message from O2" or something which isn't the same as a P0431 or P0421 (which also need to be cleared and affect readiness)

Joec500

Yup this was me! I noticed after flashing to the tune, the catalyst monitoring was set automatically with zero drive cycles which is impossible without a tune modification.

Joec500

YUP that's what I have being delivered today! Will report back as soon as I get them on