Hello Everyone. Well, it finally happened - the P0431 code on 2001 Montero (full size) with 176+k miles on the odometer. The code is a "Bank 2 cat converter efficiency below threshold". From reading multiple posts on the web sounds like I just have an old (tired) converter that had deteriorated in function over time. I've ran all required O2 sensor checks and a Mitsubishi test drive pattern for checking cat converter operation. O2 sensors are good and working properly. The test drive pattern resulted in setting the DTC code for cat converter Bank 2. The vehicle fuel delivery is within spec (NOT running rich), thus the converter failure is not due to getting it flooded with unburnt fuel, it is just due to age. Please do not suggest to replace the O2 sensors as a possible fix. As I said - I've checked them and they are fully operational. Unfortunately, I'm out of luck on this one.

I'm looking at replacing the converter Y pipe (two front converters on the Y pipe). Mitsubishi OEM is of course much more expensive than the aftermarket ($900+ vs $300-$500). So here is my dilemma - I intend to keep the truck forever and then keep it some more after that. So far, I've been using only OEM parts for all repairs and they've held up remarkably well. Should I do the same for the cat? There are millions of posts on the web, with people having trouble after installing aftermarket converters and I want to avoid this if at all possible. I am a kind of person that can't ignore the CEL after repair - it will drive me nuts, especially if i spent bunch of money to fix it.

Does anyone on this forum HAD CAT CONVERTER REPLACED? I'm especially interested in the cases involving Monteros. Please share your experience - OEM or aftermarket replacement, how did replacement work, how many miles you've put on your vehicle after replacement and how is it holding up.

Sorry for the wordy post. I'm looking forward to hearing for you all. Thanks.

 

Go buy u a bottle of cataclean run it threw it I had same pblm it helped mine

 

I actually thought of trying this. I am a bit skeptical, but I have the a bottle of CataClean sitting on the work bench waiting until my tank is at 1/4. I'm going to record O2 readings before and after running CataClean treatment. I figures this way I will see if it helped at least a little. How many miles were on your rig when you tried CataClean? Will keep you posted.

 

A quick update on my catalytic converter situation. I've completed the CataClean treatment and have been driving my Monty for some time before posting. So far so good. The treatment seem to have worked. I have burned couple of tanks of gas since the treatment and the Check Engine light did not come back yet. The O2 readings (post converter rear O2) did improve a little. I'm still getting some fluctuation on the rear sensors but it is much less prominent than before the treatment and i guess that it more closely to what computer "likes".
It may be just a temporary fix, but at the very least it buys me some time before I have to break the piggy bank and get the cat replaced. At the same time it do not have to drive with the CEL ON until that point.

 

Well... It looks like previous post was too early. My P0431 code is back. Same issue - bank 2 cat below efficiency threshold. CataClean - fail. I will be looking for a replacement Y-pipe. I'm still trying to figure out whether to go with OEM or aftermarket. I'm leaning towards OEM in order to avoid potential issues shortly down the road.

 

Take a look at this ad that came up on this page. It talks about electronic oxygen sensor simulators and extension tubes:

O2 Spacer - Oxygen Sensor Spacer - CEL / MIL Fix - Oxygen O2 Sensor Adapter - O2 Sensor Extender

 

Hunter how exactly did you check your O2 sensors. Is there a tool or special meter reading I have to do to check them...tks for all your posts as they were helpful...Mitch

 

I had the same problem on my 2004. I purchased four oxygen sensor spacers, not anti-foulers, and installed them all myself. Problem solved!

The reason for not buying the anti-foulers is that although slightly cheaper, you have to drill them out to accept the head of the oxygen sensor.

 

I have a scan tool (AutoEnginuity) which provides live feel of the voltage readings form the O2 sensors. You can graph them and see how they behave. I think it might be possible to measure output using a voltmeter, but i think fluctuation frequency on the sensors is too high and you will only get an average reading, not a true reading. You can also monitor sensors via an oscilloscope.

 

New to this forum, bought a Sport yesterday and was researching when I stumbled on your CAT question.
YOU CAN CLEAN THEM! The gas additive you used is a light cleaning. To thoroughly clean them, you have to remove them, block all holes and fill them with a laundry detergent and water mix. Let them sit at least overnight and rinse them out.
I also have a ford 5.0L w/ 4 cats... It would barely run because the cats were clogged. I did this and WOW what a difference. I haven't had to touch them since (done 60k ago, now at 210k).