Annoying P0420 CEL

[sweetpea]

So I've gotten this P0420 CEL about 3 times over the last few months. My guess its due to the mods from the previous owner.


-gruppe-s UEL header and overpipe
-invidia resonated front pipe
-Perrin 3 inch cat back


Has anyone had luck with getting rid of this code. I saw all over the net things ranging from reflashing the ECU to remove this code all together to getting the rear 02 sensor extension kit to take the sensor out of the flow a little more.


Any thoughts?


Note: I haven't seen any kind of performance or running difference in the car. Only that I lose cruise control when it happens. I've reset the light just to be sure it was a consistent code.

[D_Thissen]

Are you still running the stock tune? If so, you'll keep getting that CEL.

[DrButtDrugs]

It's because you are running a catless header on the stock tune. Cheapest fix is an OFT (can buy used for $400) which will clear your code and give you a nice bump in performance.

[sweetpea]

No idea what tune I'm running (part of the problem buying used).


How does one go about getting a new tune. I'm new to all this. Honestly I'd be scared to do an OFT without someone knowledgeable showing me what to do.

[VoltsFRS2013]

I actually just got a P0420 and took it to the dealership to get my oem headers replaced.

If you're running non catted headers you're going to get that code inevitably no matter what until you get it tuned. That's why when most people buy headers they follow it up with a tune.

It's also important to note that out of the TWO cats on your car the only one that has a sensor is located on the headers. For future reference at least keep that in mind

[sweetpea]

I'm doing some research on OFT's


http://www.ft86speedfactory.com/open...-oft-1851.html


No idea what is good/bad nor do I know what I need to modify to bump performance or keep the CEL from coming back.


How do I find out if I had a tune already?

[extrashaky]

Originally Posted by sweetpea

Honestly I'd be scared to do an OFT without someone knowledgeable showing me what to do.

Call the guy who makes the OFT. I've never dealt with him personally, but he has a good reputation on here for responding to questions and issues and has walked people through it before. There is also plenty of discussion of the product on this board, so a search will give you enough info to put your mind at ease about it. There are even videos on YouTube of people flashing their cars. Looks pretty easy to me.

[sweetpea]

Step 1.....trying to determine if I have a tune of any kind and the brand it was done by.

[VoltsFRS2013]

Originally Posted by sweetpea

Step 1.....trying to determine if I have a tune of any kind.

How long ago did you buy the vehicle and do you know who you purchased it from?

[sweetpea]

4 months ago. Haven't spoken to the guy since. I'll probably try to contact him

[Tcoat]

Originally Posted by sweetpea

Step 1.....trying to determine if I have a tune of any kind and the brand it was done by.

Paging @steve99

[steve99]

You will need a device like tactrix or an oft or ecutek or toyota techstream to read the ecu contents or at least read a parameter called CVN or checksum value number. Anc fhe ro calibration id. You then compare the cvn with the stock rom cvn if its different your tuned.

But id guess if you have catless or any form of aftermaket hesder and your tripping the xst efficiency cel code p0420 then tune is stock. First rhing any tuner does is disavle p0420 cel code

You can try o2 spacer in REAR02 senzor, they only cost $10 and pretty eady to fit, if you want to try to eliminste code without tune

[sweetpea]

Thanks everyone. I'll probably try the spacer idea first before I do any tuning or checking to see if its tuned. Weather is turning cold here in Ohio and I won't drive much in the winter anyway.


**I do have an update though, I got gas today and after I was done the light went out (so the light came on during highway type driving and 1 day later after getting gas the light came off). I've had the light come on a total of 5 times over the last 3 months. Twice it came on right after I got gas. First time I unplugged the negative terminal to clear it (didn't get the code first). Next time I had scheduled an appt with Subaru figuring it was the gas cap but after 3 days the light went out and the service guy said they would charge me $110 to read the computer and if there was no light it would probably be a wasted visit as they wouldn't find anything so suggested canceling (again it never got read). The next two times came on while city driving and I went to autozone and borrowed the tool to get it read and then cleared it myself. I have found that the cheap $49 blue reader they have won't connect to my car. I borrowed the more expensive version and it still has problems connecting, but if you hold the plug just right where it connects to the car it will read.


So could this have anything to do with the gas cap? I could replace that pretty easy as well and I've read some BRZ's had issues there.

[sweetpea]

Been about 8 days or so. No light. So its definitely an intermittent issue. I would think if I didn't have some kind of tune that it would come on more regular.