Hello, I have researched your entire website with regards to the Catalyst and O2 Sensors and retrieved and printed alot of very good information, but I still have some questions and hope to get some feedback.

My mom has a 2002 Lancer ES that has the check engine light on, we retrieved the codes 0421 (which I have seen in reference to the PDF on Warm Catalyst) and 0135. We had the PCM updated per the recall at 80K of course now the vehicle has 106K and the light came on at about 103K. I called my moms local San Antonio Mitsubishi dealership and explained the brief history. I asked them, "although the codes where not present at the time of the PCM upgrade, it is my belief that since the current codes are in reference to that all that is involved with the recall and because the vehicle ran 80K on the original PCM settings that it is not out of logic to believe that if the components which are now showing as failing with the codes provided should be covered by mitsubishi unless upgrading, accidents, etc are proven to be the cause". They told me no that I am basically screwed.

So, prior to my indept research on this site I had gone ahead and purchased Bosch o2 sensor replacements (not to thrilled I am going to have to splice but my mom can't afford $200+. I serious believe that this will not solve the problem and that I will have to replace the cat. If this ends up being the case, I understand there are two cats which I have seen, one at the manifold, and another underneath at the exhaust. Where do you suggest I purchase these parts, and do you believe this can be an at home job. I have restored older corvettes with my dad, brake jobs, etc. But I am visiting and would like to stay away from surprises so I can ensure it's done before I travel back to Florida. Any suggestions and updates would be greatly greatly appreciated.

i dont get what you are asking.

but heres some info:

-2 cats: one is a warm-up cat right after the manifold, one right after the downpipe.

-2 O2 sensors- one on each cat.

-I had to chage out the first O2 sensor, got it for 30 bucks online, changed it by myself. yes I did have to splice but it wasnt a big deal at all. took 20 minutes.

-your P0421 number means you need a new warmup cat



if u need anything else let me know. again, i really couldnt find a question in there.... of what u were asking. but ill be glad to help you.

ps. changing an )2 sensor is a job u can do at home... but u gotta get a new cat (for free) at a dealer.

thanks, thats exactly what I wanted to know, which cat i needed to replace. Also would you happen to know where I can get one that does not cost as much as the stealership?

I had already called the dealer and we are over 100k miles they cover. I need to get that part asap as I am leaving in a week back to orlando, if anyone has any ideas please let me know where I can get a replacement at a reasonable cost.

no sorry man i wouldnt know off the top of my head, either look around online or *gasp*... take it to the dealership... sorry mate

Thanks for the advice, I ordered the upper cat $425.00 shipped (lets see if they send the right part), and hope to get it by Friday. I will update on how the replacement went, again thanks for the info.

Guys, our 02 OZ Rally has the 0421 error with a check engine light. Not the upper O2 sensor. The dealer states the CAT was only covered to 80 000 miles, and were out of luck. I have heard the CAT was covered under warranty till 100,000 we now have 95000. Who can I contact about this??
Any suggestions are appreciated.. Thanks