P0430 & P0420 Code: Catalytic Converter?

First of all I'd like to say to all who read this: NEVER go to Pep Boys for ANY service or engine work! EVER!

After I paid them $570.00 for a Rebuilt Alternator and my battery that had another 6mos left on a 3yr warranty, I drove about a block before my chk eng light came on. Brought it back and they said that I would have to pay $100.00 for a diagnostic on my electrical system. Whatever! It was only supposed to take an hour but it took ALL DAY! In the end he told me it was the CAT/CONV but couldn't tell me if it was the forward CAT $1,200.00 or the aft $700.00. But the repair cost he seemed to know by heart.

Needless to say, I do not trust them at all.

Question: NOW WHAT?

ALL SUGESTIONS WELCOMED

Current mileage 155K

 

Also, had a friend of mine clear the code and my light went off but came back on after 50 or so miles.

 

ok so I understand - There are two codes, they are P0430 and P0420? These codes only came one after you had a new alternator and battery installed and you have never had said codes before?
Assuming what I understand to be true I would start with checking the wiring to the O2 sensors.

I would assume they fucked something up directly related to the cats. They may have somehow connected the new alternator wrong. It is possible that said alternator has a fault and is somehow screwing up other systems, its doesn't happen to much but since the codes appeared right after a new one was installed in my opinion it is a option.

I do not have a lot of experience with cats, but at my old shop I remember for this we would clear the codes and see how long it took for them to come back and if only one or both would come back.

That is my thoughts but first look at the O2 sensors and wiring.

 

Yes Joey,

I have heard that to change the O2 sensors via process of elimination and if it solves the problem then that would clearly be a most cost effective solution. However, if I do have to replace it the aftermarket pricing for California rated devices is all over the place to say the least. Do you or anybody have any recommendations?

Thank you for responding.

 

I am not sure where you got that I said to change the O2 sensors, I said to check the sensors. If memory serves the O2 sensors are what would report the codes that you said are present, thus they are a possible culprit and worth checking.

Check - examine (something) in order to determine its accuracy, quality, or condition, or to detect the presence of something.

 

Hey, I just changed my alternator and I am now getting the same two error codes, i reset the codes and they popped up about 25 miles later. How do I check my o2 sensors, I mean what am I looking for to tell me they are bad/wrong?????