P0431 2004 Mitsubishi Outlander 2.4 Mivec

Hi Freaks!

I have a 2004 Mitsubishi Outlander with the 2.4l 4cyl engine here.
Recently, i've changed both upstream O2-Sensors because the heater was broken on both. After few days, the P0431 came up (Warm Up Catalyst Efficiency Below Threshold- Bank2). The car has 213'000 Km (133'000 miles)

How can i check if the catalytic converter is bad or the Downstream-sensor at bank2?

In the attatchment, i have stored the freeze-frame datas and recorded live-datas from all 4 O2 sensors.
Can somebody help me?

BR from Switzerland
Matthias

The post cat sensor B1S2 looks a bit too Up-Down active to me which likely explains your catalyst efficiency codes,

At normal idle engine fully warm I would expect the pre-cat senors to continuously go up and down between about 0.9 and 0.1 volts and back to 0.9 volts in just over a second. To put another way upstream sensor should look like the Alps -- very "jaggy" mountains. The downstream sensor should be relatively inactive more like flat land with high plateaus without the " jaggies".

The first screen capture below is normal idle from a known good high vehicle with 120,000 miles on it which gave excellent tail pipe test results.







But to test the cats properly you need to use propane added into the air intake force the fuel air ratio rich for long enough to drive the fuel trims lean then suddenly stop the propane to allow it to go suddenly lean and watch how the post cat sensors B1S and B2S" respond. You can do this by introducing propane into the intake

For the full procedure see this video from the Scannerdanner Youtube Channel.

Definitely do the testing that Andy suggested. If the catalyst is truly bad, you'll see a noticeable difference in the oxygen storage of bank two.

This doesn't look like a bad downstream sensor to me, but it's possible. In addition to the O2 storage, I'd also suggest clearing the codes and rerunning the catalyst monitor. If you can now get it to pass with no codes, then that would suggest a component is just on the borderline of failure.

Depending on where the downstream sensors are located, you could also try moving them bank-to-bank and see if the code follows the sensor.

Thank you Guys! This is a great direction!
Can i use the propane-bottle from my home-grill for this test?

I hope i can see the time difference on my autel MaxiSys, the autel doesn't have Cursors to compare the Timing but i can record the datastream, i hope this works!


BR Matthias

Hi all,

I did the test with propane today. as far i can see, both past-cat sensors reacting nearly identical (almost no storage-time of the propane). But it's hard to say with my Autel diagnostic scanner. I don't have a picoscope right now and with my bench-scope i can't record signals.

Without propane and at idle (engine is fully warmed up): the past-cat sensors showing almost the same signals as the pre-cat sensors. But i've noticed, that both past-cat sensors showing fully rich at idle, after the engine was running at higher rpm for a few seconds. after 2-3 minutes at idle, both past-cat sensors starting to oscillate again. I whould say, this vehicle Needs two catalytic-converters. What do you say?

BR Matthias

Looks like you opened the box and the cat is deceased.

The captures in my reply were taken with a cheap eBay Elm327 clone and the Car Doctor Pro Android app.

"Looks like you opened the box and the cat is deceased"


What do you mean with this? Sorry, i'm from switzerland.
BR Matthias

Your cat is dead

Sometimes jokes don't translate well this might explain it Schrodinger's Cat in a box. .. This might explain it

the heater was broken on both hmmmmmmm lets take a look at this once more amperages and voltages and maybe even resistances

Andy.MacFadyen wrote: Your cat is dead

Sometimes jokes don't translate well this might explain it Schrodinger's Cat in a box. .. This might explain it

I got it! :lol: Well done making a quantum physics joke out of auto repair.

Andy.MacFadyen wrote: Your cat is dead

My cat isn't dead!

chief eaglebear wrote: the heater was broken on both hmmmmmmm lets take a look at this once more amperages and voltages and maybe even resistances

Sorry, i was unprecise! Both sensors failed within 1 year, not at the same time! But it meant, that i've changed both and both are almost new.


at least, i have 2 question marks for me:

- why both after-cat sensors (engine is fully hot) showing rich for 2-3 minutes after a snap throttle?
i saw this the first time after the propane-experiment.

- can it be a intake air-leak too? if yes, how i can rule out this?

Sorry for These "dumb" questions, i'm a beginner in this Business and want to learn as much i can!

Thank you all so far!

BR Matthias

-

Did i something wrong or why nobody answer me? :S

Did i something wrong or why nobody answer me? :S

These are my most important questions now:

- why both after-cat sensors (engine is fully hot) showing rich for 2-3 minutes after a snap throttle?
i saw this the first time after the propane-experiment.

- can it be a intake air-leak too? if yes, how i can rule out this?


Thank you
BR from Switzerland
Matthias

hang in there buddy were listening why don't you go through all the checks again and try and get specific on symptoms and everything

i'm pretty sure that both catalytic-converters are worn out. I don't know what to test else. but i struggled over a YouTube-Video with the same P0431-Code and there was a leaking intake-gasket. But i don't understand, how to get a P0431-Code with a leak in the intake, i expect a lean-code for this. This is confusing me and i re-thougt, did i Forgot something?

Thank you guys for the help anyways.
BR Matthias