P0420 Catalytic Converter Efficiency Below Threshold

[tom_704]

So about 2 weeks ago check engine light came on with that code. It didn't really specify which bank it was coming from when I was reading the code with a scanner. I reset the code and used this exhaust cleaner thing from Advance auto parts. My Subbie has been getting below avg mpg then I normally would get. Local exhaust shops can't really help me out because unfortunately it is a dealer part only. As far as I know I have 2 cats in the Subbie. Most likely its the first one right out near the engine that went bad. I hear loud exhaust vibration coming from that area at low rpm range. Its been getting more and more noticeable. My question is what are my options here if any? I don't really want to spend $1200 if not more on just parts if I have to go the dealership way which might be my only option. Even in that case I can do all the work myself but buying the parts would still run a nice chunk out of my pocket. Its really annoying for this to happen to a vehicle with 88k on it. I drive a 2009 Legacy 2.5 none turbo. I also called Subaru of N America was basically told to go to the dealer and have it check. Then to Fwd the information to them. As far as the warranty for my vehicle its 8 years or 80k miles for the cats. I do live in NY so there goes that stupid emission law against me as well. Good thing is inspection isn't due until May so I still have some time to figure this out.

 

One more thing guys. I always used 93 in this car since I bought it. Could the higher octane in the gas destroy they catalytic converters prematurely? I've used 93 in my old Honda never had a problem.

[GEE-OTTO]

Hold the phone I am here

 

1.The rattle is the stock heat shields all us 2.5i owners have that damn rattle. Have a shop cut it off completely. Also cut the shielding off the stock cat-pipe where the second cat is located it all rattles it all must go or be tack welded in place, you choose.

 

If you want to inspect the cat take it off and visually inspect the substrate it should be intact and white, if it is black and dry thats carbon due to less than optimal upstream conditions (bad fuel mixture as a result of bad AFR <Air Fuel Ratio> senor.

 

If it is black and there is residue around the exhaust ports or inside the runners you have a fluid leak upstream if its sweet smelling its coolant if not its oil.

 

If the comb is intact:

 

2.Replace both orange (AFR) and gray (O2) sensors.

 

3. Reset ECU and go for a 30-45 minute drive on a freeway, your car will idle rough, die at stoplights and suck the first few miles after a reset do not panic .

 

 

If that cat substrate is cracked and detached from the metal housing look over on NASIOC for a replacement manifold. Those 2.5i owners have been ditching stock for UELs for years, low miles same fit much cheaper than new. Look for 2006-09 NON turbo stock manifold. Its 9 bolts and two sensors to remove and replace, get a new set of exhaust port gaskets for peace of mind

 

That cat will outlast your car, any cat for that matter should.

[BarManBean]

For the heatshields, rather than remove them you can also just get some large hose clamps and cinch them up around the shields--should hold them in place fine.

 

+1 on finding a used converter on nasioc--or even going with an aftermarket replacement.

 

If you *DO* end up finding that yours is bad, get in touch with me and I might be able to give you some cash for it.

[apexi]

Your 2009 legacy is probably a pzev model. Also since you live in NY (a pzev state), you should have a 15 year, 150k catalytic converter warranty.

 

I'd talk to subaru about the WQD-40 program, they replace your front catalytic converter for free. When subaru replaced mine, they installed all new bolts in my existing heat shields, which should take care of your heat shield rattle problem.

 

http://www.wqd40.service-campaign.com/

 

Using 93 octane shouldn't have caused the problem, but I would switch to 87 octane since using 93 is unnecessary in our non-turbo engines.

[Max Capacity]

What he said ^

[tom_704]

Thanks for the info guys. I called Subaru of North Ameica. My vehicle dose not fall under the 150k warranty. Basically the rep told me schedule an appointment with your local dealer have them diagnose the car. Then to basically inform him of the appointment. He would call them and talk to them about their diagnoses while the vehicle was there being looked at. Now my only issue is if I do end up going that road and actually brining the car in. The dealer won't see a check engine ligh on. I turned it off wih a scanner lol. SUBARU of North America said they will try and help depending on the diagnoses that the dealer will give. I guess I'll go that route see what happens. After all I'm just wasting say I think $60 for them to diagnose the issue

[Max Capacity]

Drive it till the CEL comes back on, it shouldn't take long.

[apexi]

Hopefully subaru will end up helping you out, and paying for the diagnosis as well. I could be wrong about this, but I think I've read or heard that subaru can see what CEL codes the car has thrown in the past. So even if you go in there and the CEL isn't on, they might still be able to see that it has come up before.