P0420 how to get rid of

[drewmandrew99]

Alright fellas I bought a 2009 subaru legacy 2.5gt that had a cobb downpipe and exhaust when I bought it, installed the stage 1 tune off cobbs website, now I'm getting the P0420 code which sends the car into limp mode and I have to re-flash the ecu. The code is for catalytic converter however the car does now have a catalytic converter anymore. How fix?

[GearJamr]

downpipe requires stage 2 tune.

 

[m sprank]

Obviously your car has the dreaded soap on the intercooler diesase.  It is now a paper wieght.  Your only recourse is to sell me the car, I offer $501 usd cash money.

[Infosecdad]

If you picked up one of the new(er) COBB tunes they are no longer blocking the P0420 codes due to federal/CA regulations.

Is it a catless downpipe or just a HFC downpipe?

[Pleides]

On 3/18/2023 at 9:45 PM, drewmandrew99 said:

Alright fellas I bought a 2009 subaru legacy 2.5gt that had a cobb downpipe and exhaust when I bought it, installed the stage 1 tune off cobbs website, now I'm getting the P0420 code which sends the car into limp mode and I have to re-flash the ecu. The code is for catalytic converter however the car does now have a catalytic converter anymore. How fix?

This is probably something you should have done a bit more research before committing to doing. With Green Speed changes for Cobb, they no longer tune out catalytic converter-related codes. You need a Gesi downpipe with a CARB compliant catalytic converter.

[drewmandrew99]

17 hours ago, Infosecdad said:

If you picked up one of the new(er) COBB tunes they are no longer blocking the P0420 codes due to federal/CA regulations.

Is it a catless downpipe or just a HFC downpipe?

Yeah lol found this out after it arrived and dowpipe is catless. at least the accessport lets me reset the ecu code every time it pops up. Weather is warming up though and was able to drive around for a while today and havent seen it yet so fingers crossed maybe itll just be a winter problem as a michigander

[drewmandrew99]

Also from contacting various tuners off of cobbs pro tuner list ive found none of them so far are willing to tune out this code. if anyone knows of software i could use to import the cobb map into and edit to remove the code? not even sure if thats a posibility but yk.

[Pleides]

2 hours ago, drewmandrew99 said:

Also from contacting various tuners off of cobbs pro tuner list ive found none of them so far are willing to tune out this code. if anyone knows of software i could use to import the cobb map into and edit to remove the code? not even sure if thats a posibility but yk.

Open source software is the way to go here. I don't particularly care to name the software as I do think the EPA monitors a lot of these forums these days (not to sound too conspiratorial but you can see why we'd hesitate to mention it, right?) but the stuff is out there. Tuners do not tune this code out anymore because the EPA has a heavy hand when dealing with these tuning shops. Your best bet is to return the downpipe if possible and get a Gesi catted one from Cobb or Grimmspeed. The code will always come up regardless of the weather with no catalyst but cold weather may tend to increase it's propensity to give you a warm amber glow. 

I'm not sure how you managed to actually come across a catless downpipe these days unless you bought it used but hey, that's the risk you take buying a used part. Also, the inclusion of a Gesi cat is not always a 100% success rate for eliminating that code, but it helps. Leaving your factory TGVs alone as well as any other emissions systems will help you there. 

 

Also, FYI, constantly resetting the code will prevent your car from being "emissions testing ready" when doing DEQ or whatever equivalent you have in Michigan. 

[m sprank]

Or just be rid of all your troubles and $501 richer.  LOL.

[drewmandrew99]

55 minutes ago, Pleides said:

Open source software is the way to go here. I don't particularly care to name the software as I do think the EPA monitors a lot of these forums these days (not to sound too conspiratorial but you can see why we'd hesitate to mention it, right?) but the stuff is out there. Tuners do not tune this code out anymore because the EPA has a heavy hand when dealing with these tuning shops. Your best bet is to return the downpipe if possible and get a Gesi catted one from Cobb or Grimmspeed. The code will always come up regardless of the weather with no catalyst but cold weather may tend to increase it's propensity to give you a warm amber glow. 

I'm not sure how you managed to actually come across a catless downpipe these days unless you bought it used but hey, that's the risk you take buying a used part. Also, the inclusion of a Gesi cat is not always a 100% success rate for eliminating that code, but it helps. Leaving your factory TGVs alone as well as any other emissions systems will help you there. 

 

Also, FYI, constantly resetting the code will prevent your car from being "emissions testing ready" when doing DEQ or whatever equivalent you have in Michigan. 

yeah bought 1 owner at 70k miles and research ive done to figure out previous owner pretty sure he died and it was in storage since 2017ish so idk if thats pre epa shit

[m sprank]

Yes, that was just the beginning and Cobb had not yet been affected other than where they could ship/sell parts. 

[KZJonny]

There are pre ‘Green Power’ maps around if you look hard enough.

Just OTS stuff, but maybe they’ll be more forgiving of the catless DP. Maybe not. You might be able find someone who has a similar piece of hardware and no other mods to get a copy of their map from?

Probably easiest to install a catted DP tho. You can probably still find someone to buy the catless, and not lose too much money on it.

You’re not making more power without the cat, and aside from the trouble codes and inspections, your car will smell better, and not have such hard to clean exhaust mess!

[drewmandrew99]

52 minutes ago, KZJonny said:

There are pre ‘Green Power’ maps around if you look hard enough.

Just OTS stuff, but maybe they’ll be more forgiving of the catless DP. Maybe not. You might be able find someone who has a similar piece of hardware and no other mods to get a copy of their map from?

Probably easiest to install a catted DP tho. You can probably still find someone to buy the catless, and not lose too much money on it.

You’re not making more power without the cat, and aside from the trouble codes and inspections, your car will smell better, and not have such hard to clean exhaust mess!

yes but at the same time brapppppppp

[KZJonny]

Undeniably true. Hah!

I went the other way with an EL header and a relatively quiet exhaust.

I’m trying to stay in my neighbours good books!

[drewmandrew99]

only complaint from 1 neighbor so far lmfao and it was a fellow subaru owner disappointing tbh xD but at this point I suppose im trying to find a good tuner in the midwest area that could help me out preferably MI or IN 

[kzr750r1]

Cobb is at least attempting (as claimed in the parts descriptions) to wither be CARB compliant or in process if applicable.

I don't see any other manufacturers spending the money to do this.

If you must keep this cat only DP go open source and find a tuner who is seasoned.

Kicking myself for selling a unused cobb dp.

But was already tiering of swapping parts every test cycle.

Far as I've read for my car they have reached 50 state compliance for are the AP, Up pipe, BOV, Turbo intake, SF intake kits, AOS (Hmmmm, This one surprised me).

Three port boost controller and DP testing???

Wish them the best on this effort. Now only if GS and IAG would do the same.

 

[drewmandrew99]

Solution found although not convenient. I was browsing a random subaru forum from 3 years ago and found a random guys email from my hometown who is retired but tunes subarus. Will be meeting with scott to open source tune it on either this saturday or the saturday after weather depending.

[kzr750r1]

Good deal. Hope it works out for you.

[drewmandrew99]

Alright update time! I think I need a new ecu so hitting up the old scrap yard. Got together with a tuner Saturday to try to open source tune the car. After multiple attempts we finally got it to read the stock map for the car after getting com port errors over and over which was weird but then when attempting to flash a new map onto the ecu were hit with a 'j2534' error and the flash would stop but the car stayed cycling in diagnostic mode. We made sure the COBB AP was unmarried by installing it again and unmarrying it a second time but still no luck. The car is a 2009 and we were using ecu definitions for the 2007 however I did notice that when pairing the COBB AP it identifies ecu as 2008-2009 so i'm also wondering if the 2009 model has separate ecu definitions from the 2007.

[Pleides]

4 hours ago, drewmandrew99 said:

Alright update time! I think I need a new ecu so hitting up the old scrap yard. Got together with a tuner Saturday to try to open source tune the car. After multiple attempts we finally got it to read the stock map for the car after getting com port errors over and over which was weird but then when attempting to flash a new map onto the ecu were hit with a 'j2534' error and the flash would stop but the car stayed cycling in diagnostic mode. We made sure the COBB AP was unmarried by installing it again and unmarrying it a second time but still no luck. The car is a 2009 and we were using ecu definitions for the 2007 however I did notice that when pairing the COBB AP it identifies ecu as 2008-2009 so i'm also wondering if the 2009 model has separate ecu definitions from the 2007.

Yes, the 2009 is a whole facelift with, I believe, different emissions systems than earlier cars (EGR?) as well as traction control that can't be turned off (I think it can in your 07). My car is an 05 so apologies for guessing on a couple points here. You should get an ECU from a 2007 MY car. What was wrong with your old ECU to necessitate replacing it? A P0420 code is not a symptom of a bad ECU. 

[KZJonny]

Yuuup. That ECU is not gonna work.

I was surprised to know that even between ‘05 and ‘06, the maps are not the same, Despite both being the same engine configuration etc… or at least Cobb has a different map for the two years.

[m sprank]

Wow the cars have been raped, mutilated and completely f@%cked by past owners now. Sad days.  So many people working on/modifying cars that should not be. Mother nature needs to step up her game on weeding out the weak. 

[Infosecdad]

You should try with 2009 definitions before dropping the coin on another ECU.

 

[drewmandrew99]

On 4/16/2023 at 3:51 PM, Pleides said:

Yes, the 2009 is a whole facelift with, I believe, different emissions systems than earlier cars (EGR?) as well as traction control that can't be turned off (I think it can in your 07). My car is an 05 so apologies for guessing on a couple points here. You should get an ECU from a 2007 MY car. What was wrong with your old ECU to necessitate replacing it? A P0420 code is not a symptom of a bad ECU. 

I just refuse to revert the car to stock exhaust but yes started with the code and using rom raider you are able to read from the ecu but not write to it would just continue to cycle in diagnostic mode after throwing an error code and stopping the write on rom raider.

[drewmandrew99]

12 hours ago, Infosecdad said:

You should try with 2009 definitions before dropping the coin on another ECU.

 

Source?