P0420 after AP Stage 1

Hey All, sorry if this question has been asked before, I did search around a bit but could not find a similar issue, in any case: good old P0420 started popping up this week after installing the Cobb AP stage 1 (93 octane) on my 05 LGT with about 150k on it. Never once saw this code before the AP, so I'm a bit suspicious.... But at the same time, I believe the car has the stock cats on it, so it seems reasonable that the new map just pushed it over the edge...

 

Has anyone else experienced this?

 

Only mods are a turbosmart Kompact bov, FMS DP back exhaust and lightweight crank pulley. Up and down pipes are stock.

 

Frankly, needing a new cat wouldn't break my heart, kindof sounds like the perfect excuse to go stage 2

 

Thanks

Alrighty then! Thanks for all the help, ordered the GrimmSpeed UP/DP combo yesterday.

Was it running another map without your knowledge with the P0420 code turned off?

You know, that is entirely possible.

Othe car was definitely modified a bit before I got it at 100k (it had a boost gauge and LW crank pulley when I got it). And when I loaded the AP in it did mention that it detected a previously loaded map. So yeah, that could be it.

 

Either way, it's pretty clear that the car needs a new cat right?

Either way, it's pretty clear that the car needs a new cat right?

 

I don't know. No expert here on knowing when a cat is bad, although it is my impression if a cat is bad the engine boggs down and looses power. I'd hate to recommend you spend money if it is not needed. My car threw that code within a week of putting on a band new high flow Invidia catted DP. Others in the 5th gen forum have the same DP as I, but do not throw it. I had to get mine tuned out.

 

If you are tuning with an accessport. You should be able to download Accessrace Tuner (ART) from Cobb, load your map, then uncheck that code box within ART, resave it, load it on your AP, then reflash your car. Unless you are familiar with tuning, I wouldn't mess with anything else. Another option is to get an e-tune from another tuner on here, have them tune it out (this might be your best bet if you are uncomfortable); or to go get a pro-tune at a place with an all wheel dyno and Subaru friendly. However, that just a way to ignore a potential problem --- if there is one.

 

It might be worth checking to make sure the sensor is hooked up and functioning properly (how--notsure??). 150k miles is a few.

 

Proceed at your own risk.

Code P0420 on 4/20? No freakin way...

Thanks aero, I'll definitely look into the accessrace tuner from Cobb. The up and down pipes are already on order, they'll be in the car in about a month or so... So we'll see what happens then.

Gotta love that good ole 420 code.

 

I agree with Aerophool, generally a bad cat, is a clogged cat. But, then that ole 420 code is annoying as heck to track down and solve. My old Impreza had that on and for the life of me, i couldnt get it to go off.

Update:

 

Been running the car with the Grimmspeed up/catted down pipe combo for a few hundred miles now on AP stageII and so far, no P0420. Dare I say, I think it worked.... *knock on wood*