I'm calling it a night so if you need more help, Seduction, just let me know. If the dealer didn't fix your problem then I can tell you how to do the drive cycle as well.

IF the dealer didn't replace the catalytic converter with an OEM spec. one, then he had to have flashed the PROM and sent you on your merry way. I'm confused though as to why he told you to buy a code reader. If he fixed the problem, by flashing the computer or replacing the cat. with an OEM one, then you should not get a check engine light back on for this particular code. When emissions are checked, one of the things they check is for is history codes and current codes. So, if your check engine light comes back on and you simply clear the code right before the emissions test, you may still not pass emissions. Cars have "drive cycle" times in which they self test, so to speak, the computerized items. As long as a check engine light isn't setting for something that the computer regularly checks on a drive cycle, then you may pass. If the code setting is for something it regularly checks on a drive cycle then you must go through the drive cycle again in order to pass emissions. Just clearing the code is not a guarantee of passing emissions though. Last, thought..you shouldn't have had to buy a code reader if the dealer fixed your problem.

"Flash" silly LOL!! The dealer (or shop) has to have all the right technical equipment to connect to your OBD II system. Dealers usually do. If you kept the same catalytic converter on your car, the dealer had to have flashed your PROM to reset and widen your parameters. Has your check engine light come back on? If so, then the code reader will simply erase the code, thus telling the emissions person that there is no current or stored code. This may not get you to pass emissions though because of drive cycles figured in.

Seduction--
So did you have the cat replaced with the correct one? Or did the dealer flash the PROM? (thus expanding the parameters to deal with the cat you have installed) Did you purchase an OBD II code reader online?

That is interesting. My ex has a 1967 Camaro and it was from CA, and had all the extra stuff hooked up that was required in CA. So it is not surprising, but not what a persons first guess would be.

I hope their error was of no extra cost to you.

* Has the ECM (computer) been reprogrammed at any point surrounding these services? * “the code has been cleared each time.” Clearing the code is different than reprogramming the computer. Some refer to it as “flashing”--mostly the dealers use this term. It has been known to cure this problem 98% of the time IF the only trouble code that keeps coming up is P0420. Some Subaru models are well known for this problem you are describing. It was a big enough glitch to be “known in the industry” but not big enough for a recall or a technical bulletin with specificity. It’s a complex problem so remember that I need to generalize as I don’t know yet which code or codes that your car is storing. If the only code re-occurring is P0420 then I suggest the following (which in doing this, I need to assume that you used OEM O2 sensors, an OEM catalytic converter the second time around and that it is not defective again, and that unleaded fuel was the only fuel put into the car. If not, then I could go on about these items lol)--- --visual inspection of O2 sensors to verify that they aren’t physically damaged and that the wiring is also connected securely and not damaged --check for exhaust leaks and/or damage to any exhaust components (start at the exhaust manifold and go to the tail pipe). Sometimes, not always, you can hear an exhaust leak. --have your mechanic put a scope on it to observe the O2 sensor function --this can help to eliminate the sensors being bad again (though it isn’t typical for OEM sensors to fail soon and often) --while the mechanic has your car on the scope, he/she can also check the function of the engine coolant temperature sensor to eliminate this being part of the problem. Just because it hasn’t overheated, YET lol, doesn’t take this sensor completely out of the mix. --and again, while on the scope, look at the timing to ensure that it isn’t retarded (and yes, lol this is a mechanical term also, believe it or not) I highly doubt this is your case as you’ve indicated no other symptoms. You’d have symptoms, beyond the CEL if the timing was retarded. Ok, so take this advice only if the code is P0420. If it turns out to be a different code or more than one code let me know and we will go from there.

thats what I said yesterday. Ck the cap

The only time I have had an engine light come on in a vehicle, each time it was within and hour of filling up with gas. I apparently didn't tighten the gas cap down until it "clicked" and it allowed air to get in to the tank which makes the engine line come on.

Ok, so let's get specific now. (It's much easier to do this diagnosis actually with the car in front of me lol) 1. What was the length of time between the two catalytic converter replacements? Are we talking years or a few months? 2. What is the specific check engine light code now? (most shops will tell you the number because they assume a lot of their customers don't know how to go further with that info) 3. I'm going to go out on a limb and assume that each time the converter was replaced, that the check engine light was erased and that the car was run through a drive cycle (especially after the O2 sensors were replaced and considering that you must have emission tests there). Has the ECM (computer) been reprogrammed at any point surrounding these services? 4. Are there any other symptoms, besides just the light?