Question Re. P0420, and Parts Interchange

[avk]

So I got a good ol' P0420 "Cat. converter efficiency below threshold" code on a 1995 Impreza. I have read some of the previous threads about this code, and will try to find what the problem is. Meanwhile, in case I will need a new converter (front, rear, perhaps both), I have a question about parts interchange between different years. The issue is cost. For 1995-1998 models, front and rear converters are separate parts, and cost an unspeakable fortune even at a discount. On the other hand, on later models the two converters are a single welded assembly and, for some reason, it costs less than either one of the earlier separate converters. The question is, can the later one-piece assembly be substituted for the two earler converters? I noticed that some aftermarket suppliers have the single assembly listed in their catalogs for 1995-2001. At the same time they, like Subaru, list two different intermediate pipes (but the same mufler).

Hence my question: will a newer two-cat assembly bolt on to an older intermediate pipe w/o adjusting the length and/or mounting hardware?

[xrturbo]

If your car is a 2.2 you can use the newer one peice style cat. The 1.8 cats have a 45 degree rotated flange for whatever reason. It doesn't sound like you want to spend alot of money on this ( who could blame ya), just throw an 18mm non fouler in between the O2 and the bung on the rear O2. I am running this on a 96 outback with no cats and have not gotten a CEL.

 

If you do run the newer style cat it may have both O2 holes up front, just unplug the extension harness for the rear O2. You will see it at the top of the bell housing. It just acts like an extension cord.

[avk]

Thanks a lot, this is a huge help and people should be aware of this interchange. I don't mind spending some money on it, but the separate-style converters cost someting like $520+ for the front and $350+ for the rear. For comparison, the newer style one-piece assembly is about $250, which is even competitive with aftermarket. Still hope I won't need the cat.

I have some part numbers if anyone's interested.

[Olnick]

I have some part numbers if anyone's interested.

 

Yes, please do--might be helpful to some down the road.

 

Hope you don't need the cat too, but if you do go for the "one-piece" keep us posted. Thanks, avk.

[avk]

I have one of those "Parts Quick Reference Guide" books, mine's a 1985-2001

edition (p/n MSA6P0104), and it gives the following numbers for one-piece converter assembly:

 

44139FA000 for "7/98-6/99 49 state" (which seems to mean mostly 1999 model year); and

44139FA010 for "7/98-6/99 California" and "7/99-", meaning 1999 California models and all 2000-01 models.

 

Prices are the same. If I decide to get one, I'll try the first number because it's more likely to have

the same sensor locations as the old type.

The front Y-pipe assembly didn't change, the only difference being between one and two exhaust ports,

but that change occurred in 1996, before they changed the converters. Besides, 2.5l engines remained two-port.

So it's easy to tell that the newer converters will fit on the forward end.

[gbrand]

Please make sure the problem is actually with the convertor,not the Oxygen sensors that read the health of the convertor. there was a recall on some of these, read the thread referenced below

 

Originally Posted by gbrand

http://www.ultimatesubaru.org/forum/...highlight=0420

 

please read this, all the way to bottom, you may be coverd by a recall that is casuing your problem.

[GeneralDisorder]

Try this first:

 

http://forums.evolutionm.net/showthread.php?t=215795

 

GD