: Installed American Racing Headers- ongoing CEL problems.. arghhhh

06-29-09, 08:48 PM
Had my headers and crank pulley installed with my existing WFM max performance tune and modded airbox. Within a day check engine light on. Called Nick at AR Headers and he felt rear o2 sensors need to be turned off in tune- my performance shop feels the same way and that this of course common place with long tube headers. Spoke to Jesse and he feels header design/ sensor placement is the problem. He is hesitant to delete any sensors and does not support headers due to early experimentation with them- this led him to the decision to go with the 3-inch cat back/x-pipe.
Disappointed- need solution. Jesse was kind enough to offer to place my drivers side header on his car, reposition sensor and adjust my hand held as needed- I would have to have other header modified accordingly. Second option remove headers and replace stock exhaust- wait for future dyno uning solutions close to home and replce in future. Either way still planning on adding 9.5 ring
Any thoughts on solutions to keep existing headers- sound great and good fit

BTW- OBD codes being thrown-
2-P0420-CAT low efficiency bank 1

These were all cleared and CEL came back within 1/2 hour

Thx for help/thoughts in advance

06-29-09, 09:21 PM
By the looks of those codes, the scan tool is not reporting the correct pids/vs/ actual data. 4 of those dont exsist for your platform. Can you take the car to a autozone or napa and get a free code scan?

The codes i have seen in person are only P0140 and p0420, and p0430 lately... Nick called and i told him how i make them read right so hopefully it will fix your issue as well.

06-29-09, 09:48 PM
Jesse sure I can go to NAPA or Autozone.......

So Nick at ARH called- what was the concensus between you and him?

06-29-09, 10:28 PM

Just ran a new diagnostic myself with the SCT handheld-codes as follows-


06-29-09, 11:33 PM
The rear 02 sensors need to be turned off. The high flow cats flow so well, the ECM thinks you are catless.


06-30-09, 06:09 AM
Mark - I think that Jesse is trying to find a different solution -turning off the sensors is what ARH's is saying as well

06-30-09, 09:44 AM
No need for a different solution IMO... Everytime I have had hi flow cats, always have had the rear o2's turned off. They are only there for "checks and balances". They don't modify AF ratio. Strictly for OBDII compliance and some EPA stuff.

Just my $.02

06-30-09, 10:32 AM
I had my AR headers installed at Hennessey's shop, and I believe they turned off the rear O2 sensor. I had it done 3 weeks ago -- no CEL since (and no other issues, either).

06-30-09, 11:16 AM
i have w4m exhaust(and airbox and handheld) and i constantly get the 0420 code. how do you turn off the O2 sensors?

06-30-09, 11:19 AM
i have w4m exhaust(and airbox and handheld) and i constantly get the 0420 code. how do you turn off the O2 sensors?

I have same mods you have and Don't get any codes... Surprised you are getting that code...
To answer your question, it has to be turned off in the tune that was installed.


06-30-09, 12:28 PM

The 0420 code is the CAT bank 1 sensor-low efficiency cat bank 1- the FRONT drivers side sensor- I am throwing the same code- trying to find a solution with Nick at ARH. Jesse wannts to relocate new o2 bungs on headers and not turn off sensors.

Surgin is Jesse aware of your problem? Its totally his package so their should be a solution

07-01-09, 03:01 PM
Yeah I am still waiting for the fix for my 1400 code. something for the coolant and the 160 stat. Jess says he has the tune revision for it and still i wait

07-01-09, 03:23 PM
SCT hasn't provided him with the ability for him to send tunes via email and us to upload the new tune. That is my understanding of the ordeal. They initially told him this could be done, but in reality, it can't be done yet....


07-01-09, 04:04 PM
Jesse spoke to ARH and then Nick at ARH spoke to my installer-

Jesses contention is that rear 02's should not have to be turned off and that o2 sensors should be relocated in terms of bung length and depth of sensors- thus Nick is sending my installer 2 extra bungs and we will try to eliminate p0420 code that way

To "tune out" the problem would mean to dyno tune the car and go with a different tuning software. I do not believe I want to go this direction. In retrospect perhaps headers under these constraints are a poor choice for me- I may just go back to stock with corsas.

07-01-09, 10:18 PM
I think back to stock, with Corsas, may be the best solution for trouble-free function, if your V is a daily driver. If not...I'd press on to find the solution to your problem. If it takes moving the O2 sensors, and it's not too onerous an operation, the result may well be worth it.

07-02-09, 05:51 AM
AF-agree- v is daily driver so will go back to stock mild mods- tune airbox mod intake corsas and call it a day- 500 rwhp is not too bad right.