Analytic converter?

Hey ladies and gents.

My '02 Subaru Outback, which I’ve owned for nearly 8 years, had apparently decided to celebrate the start of our July 4th weekend together with a very specific firework, the dreaded “check engine” light!! Befuddled and armed with my new swimsuit and an incredibly rudimentary knowledge of engines, I looked under the hood. Not sure what I expected to find, but what I did eventually notice was a few sizable rips/tears along the creases in the flexy hose that runs from the air intake to the filter. I theorized this might make the mixture read as “off”. So I gaff taped it to within an inch of its life (if u don’t keep a roll of gaff in your auto, you’re playing with fire)… And proceeded to enjoy my holiday. Upon arrival home, I took it to my repair shop strait away in case the issue was either serious or dangerous. This was the second time in a month it had been in that shop. The first visit was for an inspection/check-up (to prepare the car for the holiday travel actually.) and that visit happened to cost me a little over 800 bones.

So a day later he calls and says the sensor that came up on his scan was the O2 sensor and he took this to mean that I needed a new catalytic converter, which he then said ominously, could be “very, very expensive…” And then further warned “I don’t even know if u want to fix this thing.”
So the question becomes: Is it truly the catalytic converter OR could the “sucking-in” of the ambient air thru the gaps in the hose have been the actual culprit in the case of the July 4th check engine light?? Do I need to once again, weigh an expensive repair cost against the cost of buying a newer car??
Quasi-related but slightly less important question: Is my new (just moved) repair guy a bit of a shyster or is this just a natural assumption based on his sensor reading?

Any help/opinions are welcome and thank you all in advance. Apologies for the lack of brevity here.

Definitely get a second opinion. Take it to the dealer or a good inde mechanic who knows Subaru’s.

I wouldn’t trust this guy. It’s easy enough for him to give you a dollar quote, yet he didn’t. And he needs something to back up his claim it’s the cat.

If the gaffer’s tape (or duct tape to us "Muricans) is still sealing the intake split, your mechanic should be able to clear the codes and they should STAY cleared IF that was the problem. Not sure that was it, though, you don’t say if it went away.

Air Bypassing the mass air flow sensor would cause a lean fuel condition that the car would try to fix by shoving in more fuel until it could add enough. Then the error would be a Check Engine Light for lean fuel condition. That sets a specific code for “lean fuel condition” (I forget the number) not specifically a “bad O2 sensor” code.

If this is an American spec car, you would have at least 2 O2 sensors, one before and one after the catalytic convertor. An error on the after O2 sensor could indicate a bad convertor (expensive) or just a bad after O2 sensor (cheap).

As for fix or scrap, you didn’t say if the car was nice or a rat’s nest, nor did you tell us how many piles of bones the mechanic might need, worse case, to fix the old girl. A little help, please, mileage, condition, estimates for repair, did the CEL go out after the gaffer-tape repair, do you always service cars in your swimsuit? Stuff like that.

thank you very much for your responses…

Mr. Russell, Im not sure we’ll see a defensive center of your ilk ever again. I was thinking the dealer was the way to go for second opinion…

Mustangman, apologies for lack of info…

The car is “fine.” It has a sort-of, garden variety repair history… nothing terrible but nothing too exemplary either…
My mechanic didn’t feel comfortable “putting a number on it…” He said it could be as little as 1K and as much as $2500… as of today the KBB values the car at about $1900…
164,000 miles… fair to good condition…
it’s my understanding that the CEL wouldn’t go out even after the gaff tape fix unless it was cleared by the mechanic…
The swimsuit was purchased and adorned mere minutes before the check engine light came on.
I don’t always try to investigate automotive problems that are clearly out of my depth, but when I do… I do it in swimwear!!!

thanks fellas.

wrong bill, sorry.

Is the check engine light still on? If yes, take it to Autozone (assuming you’re not in California) and ask them to read the codes. They’ll give you a code, or a list of them. They will be in the format of a P followed by 4 numbers. Write them down and post them here.

If the light is not still on, then drive until it comes back on, and see above.

O2 codes trip all the time… Get a REAL mechanic to look at it. Replace that Intake hose as it is rather important…and can cause your fuel mixture to be off in one direction or the other… My guess is toward the lean range… Either direction of mixture the unmetered air can easily cause an o2 code to be thrown.

Sometimes an o2 has an issue and it then goes away…but once that code posts…it has to be cleared before it goes away permanently

Get a better mechanic…this one appears lacking IMHO


Quote; “I don’t always try to investigate automotive problems that are clearly out of my depth, but when I do… I do it in swimwear!!!”

I should try to get all of my horseshoeing clients to dress like this for our appointments.
But then I’d get nothing done!!! And those tender little feet in flipflops are a little risky around horses.

I’d definitely get a second opinion. This mechanic could have called for the prices before contacting you…then he’d be prepared to give you all the info to make a decision. I keep a list of all the parts houses in my area and the dealers parts dept phone numbers…I’m sure he does too.
I doubt it’s the Cat, I think he’s guessing.


The rips in the boot from the air filter box to the intake manifold could confuse the ECM enough to flag an O2 sensor code. That code doesn’t imply necessarily there’s anything wrong with the O2 sensor, just that the reading the ECM is getting from that sensor is skewampus, unexpected. And a torn intake boot could caused a skewampus O2 sensor reading. If this were happening to my car, I’d have the codes cleared (read them all out first and write them down), and see if the CEL comes back on. You might have already fixed this problem.

In many cars of that era there’s more than one O2 sensor, at the minimum two, one before and after the cat. Did you say which one? My comment above would apply to a pre-cat sensor. If the problem is the post cat sensor, that could be a cat problem. Not necessarily, but the cat should definitely be considered a suspect. A working cat changes the O2 concentration as the exhaust gas goes through the cat. So for a working cat, the pre and post O2 sensors will read different. For a non-working cat (or if there wasn’t a cat) the pre and post O2 sensor readings would be nearly the same. If the codes is for that, you need an experienced mechanic you can trust to determine if the cat is good or bad. The more sophisticated diagnostic scanners will have a real time mode which display the pre and post O2 sensor readings vs time, and the correct interpretation of that chart is critical to determining the cat status, good or bad.

There’s one other test a shop might do, the cat back pressure test. That would determine if the cat is starting to get plugged up, which they sometimes do as they go bad. Since you aren’t complaining of any drivability or loss of power problems, I’d probably not do that test in your case.

You guys are amazing… I replaced the hose and reset the CEL… and so far, two days in, I seem to be doing dandy… Might even give that swimsuit another go 'round this weekend… Utter gratitude for everyones opinions…

Glad it was an easy fix for you.

Happy trails