I have a 2001 Mitsubishi Montero XLS (203,000 miles) and it is throwing the P0431 code failing emissions inspection.It passed the visual/functional inspection.The service station tells me I need to replace the front Y pipe and two oxygen sensors.The cost of repair is staggering at around $1500 using OEM parts from Mitsubishi.
Does anyone have experience replacing the front y pipes and oxygen sensors with aftermarket parts?If so, can you suggest the manufacturer of quality parts which fit well?If this is a favorable option I would consider replacing these parts myself.Also, I am not in California where I understand rules are more stringent for catalytic converters.
I’m looking for a more economical solution.I historically have experienced problems with the Service Engine Soon light being on and needing to replace oxygen sensors since I purchased this vehicle in 2002.
Thank you

 

I had the same thing with my 02 Montero Sport. I put 1/4 cup seafoam in the pvc valve and the rest in the gas with at least 3/4 tank. Drove for about 30 mins above 60mph and took it straight to the emission test station. Passes every year, but the cel light would usually come back after couple of weeks. I've been doing this for the past 3 years.
Not recommending you do this, just sharing my experience.

 

O2 sensors for your vehicle run around $30 each. What is the purpose of replacing the y-pipe? I'm not familiar with your particular vehicle, but I have never had to replace an entire section of pipe to replace an o2 sensor. They are normally screwed into the exhaust pipe before and after the cat. O2 sensors are not that hard to replace. You're about to get screwed by whoever quoted you that price, imo.

 

The Y pipe on the Montero is a one piece unit that contains two catalytic converters. I am being told that the P0431 code means that one of the catalytic converters is bad. I believe the O2 sensors on that cat are being identified as needing replaced also.
Some additional research on this site suggests that the P0431 code points to the bad catalytic converter only and the fact that I am only getting this code means that the O2 sensors are fine.
I'm trying to understand my options to pass emissions testing and am looking for reliable aftermarket Y pipes, suppliers, and any other suggestions as mentioned in my original post.
Thanks in advance for any help you can provide.

 

OK,, now I understand better. I would check rock auto for replacement converters. Or buy a universal and take it to a muffler shop for replacement.

 

Does anyone have experience (good or bad) with an aftermarket catalytic converter Y pipe supplier for a 2001 or similar Montero? I'm looking for my best option for fit and function to pass emission inspection. Thanks!

 

VKR, did you find a solution? I'm having the same problem and looking for an economical solution as well.

 

Hey VKR, I've been having similar issue ('01 Montero 177k). In fact I've posted a thread "Cat Converter Blues" not long ago. One of the suggestions was to use CataClean. I've tried it and so far it worked well - check engine light is off and all O2 sensor readings are normal. I do not have to deal with emission testing, it was more for my own benefit of not having to look at the Check Engine light all the time. But I'd say try it first you may get lucky.

One thing to note - if you are getting P0431 code, you do NOT need to replace O2 sensors - they are working properly and that is why you have a cat converter code instead of O2 sensor code. Good luck.

 

I did not receive any feedback from the forum regarding aftermarket catalytic converter quality. Therefore, I purchased an OEM Mitsubishi Y catalytic on line from one of the Mitsubishi OEM part dealers. The Y-Cat and related gaskets, bolts, and nuts cost me close to $700.00. If you go this online OEM part route, I highly recommend you study the part diagrams online plus call the supplier to ensure you are ordering the correct parts. I found the part diagrams and descriptions online lacking in detail.
I replaced the Y-Cat myself in October. I was able to do so without jacking the Montero up to remove or replace the Y-Cat. Of course, this made for tight quarters and much more cursing. I did have to purchase an O2 sensor removal socket and a socket wrench extension to reach the manifold nuts.
The replacement was successful in eliminating the P0431 code. I did not have to replace any O2 sensors to pass emissions inspection. This confirms a post I saw on this forum and HunterD’s comments that the P0431 code points to a Y-Cat replacement only, not O2 sensor problems.
I wish I would have tried the Cataclean product prior to replacing my Y-Cat. It would have been worth a try. I pull a trailer and after 205,000 miles a new Cat is probably in order. No engine lights or codes since the October 2014 replacement.
Vince

 

Thanks for the update. Good to know that you are all set and all is running well. Where did you purchase the Y-pipe? The lowest price I've found for the OEM is around $900.