2002 All Other Makes All Other Models

2002 Forester, 108,000 miles.
Check engine light first came on after improperly replacing gas cap. Now comes on intermittently even when cap on straight, although currently off. Computer diagnostics indicated catalytic converter ($1100!) Is faulty (tested when light off). Would like to change (or have changed) emissions filters to guarantee these aren't part of the problem. What should be replaced?
Frank Florence
January 10, 2007.

Hi Frank,
Give us the code number pulled.
Has this been diagnosed or just presumed?

Service Writer,

The listed code is P0420 - cat converter failure.

When I was given this report, I asked what was fouling the converter and had the mechanic looked at the emissions system or filters. Also why was I getting this code if the check engine light was currently off? Did this mean that there had be an O2 problem in the past or was there currently a problem?

The reply I got was " The computer says you need a new cat convertor.&Quot; Some mechanic.

Frank Florence
Jan 11, 2007.
Catalyst System Efficiency Below Threshold (Bank 1)
This may not be a cat! Dog either: )

According to the info I have, the code needs to be cleared. And then a drive cycle performed twice.

Subaru says to not diagnose this code if it is alone.

After codes are cleared, turn the ignition key to on, but not cranking for 3 seconds to initialize the idle speed control motor.

The drive cycle involves driving for 50 mph, then stopping then car and idling for one minute. Then repeat the cycle.

Useful information! Thanks.

However, I don't know how to clear the code. Is this something I can do? Or would another service center be able to do this?

I have no confidence in the Subaru shop that gave me the initial estimate so I'm not excited about going back to them. I got the feeling that all they really wanted to do was sell me parts (versus solve a problem.)

Frank Florence
Jan 11, 2007.
I don't know how other than using a scanner. I do know that autozone has done this for free in our neck of the woods. An independent shop can do this. I would send you to a shop I know but that would be geographically challenged :)

What I suggest if you can't find one through a source you trust, is to contact the local snap-on dealer tool dealer, he knows the good shops and could refer you.

Good luck :)

Great. Thanks again for the help.

Frank Florence
Jan 12, 2007.