Frankzao Posted February 29, 2008 Report Share Posted February 29, 2008 Does code P0431 really mean this: P0431 OBD-II Trouble Code Technical DescriptionWarm Up Catalyst Efficiency Below Threshold (Bank 2) What does that mean? Basically this means that the oxygen sensor downstream of the catalytic converter on bank 2 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system. Symptoms You will likely not notice any drivability problems, although there may be symptoms such as a rough/hard idle when cold. Causes A code P0431 may mean that one or more of the following has happened: The catalytic converter is no longer functioning properly An oxygen sensor is not reading (functioning) properly There is an exhaust leak I got one. I cleared it and it has not returned. Any thoughts? Quote Link to comment Share on other sites More sharing options...
Renboy Posted February 29, 2008 Report Share Posted February 29, 2008 That description is basically right on. Quote Link to comment Share on other sites More sharing options...
street3890 Posted February 29, 2008 Report Share Posted February 29, 2008 I also have the same code, along with. p1525 which is something with the abv Quote Link to comment Share on other sites More sharing options...
MazdaMomma Posted February 29, 2008 Report Share Posted February 29, 2008 possibly clogged cat or it is corroded. check that out and see what happens. Quote Link to comment Share on other sites More sharing options...
Frankzao Posted March 1, 2008 Author Report Share Posted March 1, 2008 so how do you tell if it is the O2 sensor or the CAT. My S only has 73K on it. Quote Link to comment Share on other sites More sharing options...
Renboy Posted March 1, 2008 Report Share Posted March 1, 2008 Not sure if the harness on the o2's are long enough, but you could swap the downstream sensors (right - left) and see if the code follows. If you end up with a P0421, then it's the sensor. Quote Link to comment Share on other sites More sharing options...
Frankzao Posted March 3, 2008 Author Report Share Posted March 3, 2008 Good idea. I'll wait and see if the code returns. I could always run an extension on the wires. Cheaper and easier than replacing a good O2 sensor...... Quote Link to comment Share on other sites More sharing options...
latinopikachu Posted March 4, 2008 Report Share Posted March 4, 2008 chevron with techron Quote Link to comment Share on other sites More sharing options...
Frankzao Posted March 6, 2008 Author Report Share Posted March 6, 2008 for? Quote Link to comment Share on other sites More sharing options...
Frankzao Posted October 4, 2008 Author Report Share Posted October 4, 2008 Update THe P0301 and P0431 codes returned..... I have 79K on the milly now. Cleared the codes and no return.......again. Quote Link to comment Share on other sites More sharing options...
///BHRpowered Posted October 4, 2008 Report Share Posted October 4, 2008 301 would be cylinder 1 misfire, I assume you've already switched the coils? and atleast checked the sparkplugs? no oil leaking down onto the plug or anything? 0431 Basically this means that the oxygen sensor downstream of the catalytic converter on bank 2 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system. A code P0431 may mean that one or more of the following has happened: * The catalytic converter is no longer functioning properly * An oxygen sensor is not reading (functioning) properly * There is an exhaust leak Might be time to replace the cat....with a high flow one and a custom exhaust Quote Link to comment Share on other sites More sharing options...
Frankzao Posted October 4, 2008 Author Report Share Posted October 4, 2008 Might be time to replace the cat....with a high flow one and a custom exhaust That is what I'll do when the time comes...... Quote Link to comment Share on other sites More sharing options...
Matt64341 Posted October 6, 2008 Report Share Posted October 6, 2008 the high flow cat replaces the cat that is not monitored by the ecu, so it would not be throwing that code. If it was not the oxygen sensor, than the code would be for one of the pre-cats Quote Link to comment Share on other sites More sharing options...
Frankzao Posted December 16, 2008 Author Report Share Posted December 16, 2008 Update THe P0431 code returned..... (few months ago) I have 80K on the milly now. Drove thru some 12 inches of water yesturday on the way to work (not on purpose)..... rained like cats and dogs yesturday. CEL started flashing continuously......car started to stall.....but the milly kept going...fortunately I was only a block or two from my work.... Car started fine after work and I drove it home just fine .... CEL flashing the whole time...... When I got home pulled the code P0301......Cleared the code and no return.......again...... I guess some water got up to the coil pack.... gotta luv the milly....she'll keep running no matter what!!!! Quote Link to comment Share on other sites More sharing options...
mts Posted December 16, 2008 Report Share Posted December 16, 2008 Sounds like you have a cat carboning up from all the premium fuel you use Quote Link to comment Share on other sites More sharing options...
///BHRpowered Posted December 17, 2008 Report Share Posted December 17, 2008 falling into rens lies.... Im not sure how you would have gotton water into the coils, I mean I'v gone through deep crap in my jeep which isn't nearly as closed off up top. I would be more concerned about water in the intake really. Quote Link to comment Share on other sites More sharing options...
mts Posted December 17, 2008 Report Share Posted December 17, 2008 Not lies... you keep believing the lies from Mazda... mine is far more advanced in timing and mods than yours and I still run mid-grade WITHOUT issue. That is OK mine will be sold in the spring along with Ren's MX-6 Quote Link to comment Share on other sites More sharing options...
Task514 Posted December 17, 2008 Report Share Posted December 17, 2008 Sounds like you have a cat carboning up from all the premium fuel you use If that's the case... then why just bank #2?! I have the same problem... (P0431 with cyl #5 misfire) seems to be on bank #2 also. btw which one is bank #2? talking of Exhaust leak... some of my flex pipe's metal braiding has come off. Would this lead to a leak?! Quote Link to comment Share on other sites More sharing options...
mts Posted December 17, 2008 Report Share Posted December 17, 2008 The other one will come too.... P0421 is soon to follow. The Miller cycle engine is a carbon producer regardless, even the great BHR's exhaust tips had the tell tale black around the edges at the meet. I believe bank 2 is the rear set of O2 sensors. If the flex pipe is losing the braiding, you will likely get a leak in the future... why has the braiding come off? Too much flex, corrosion? Quote Link to comment Share on other sites More sharing options...
Task514 Posted December 18, 2008 Report Share Posted December 18, 2008 The other one will come too.... P0421 is soon to follow. The Miller cycle engine is a carbon producer regardless, even the great BHR's exhaust tips had the tell tale black around the edges at the meet. I believe bank 2 is the rear set of O2 sensors. If the flex pipe is losing the braiding, you will likely get a leak in the future... why has the braiding come off? Too much flex, corrosion? I don't know... it look like if it just simply vanished in dust. No sign of damage. Probably corrosion Quote Link to comment Share on other sites More sharing options...
///BHRpowered Posted December 18, 2008 Report Share Posted December 18, 2008 ...and why would you even think of selling it, timing and mods? no you just have headers, thats really it that I don't in terms of performance. you should know that if there was a way for my cars to produce more hippy killing gas I would see to it, but thats not the way the millenia works keep in mind I don't sit idling in traffic with it either Quote Link to comment Share on other sites More sharing options...
Frankzao Posted December 19, 2008 Author Report Share Posted December 19, 2008 LOL.....they just tire of you master...ignore them. the milly will live on forever.... the whine of the s/c....the power in the acceleration..... I actually wonder if there is something wrong with cylinder #1.....after all, it did eat one of my plugs remember? Quote Link to comment Share on other sites More sharing options...
latinopikachu Posted December 19, 2008 Report Share Posted December 19, 2008 i'm concerned about a similar issue to that.... one cylinder has a chronic random misfire that isn't detected by the ECU but i can feel the shaking Quote Link to comment Share on other sites More sharing options...
SteveSter Posted December 19, 2008 Report Share Posted December 19, 2008 Change the coils and plugs and seafoam it, if that doesnt get rid of the problem I dont know what will. Unless its something more serious. Quote Link to comment Share on other sites More sharing options...
Frankzao Posted December 19, 2008 Author Report Share Posted December 19, 2008 I've switched the coils and the plugs...I ran seafoam thru the gas tank already....less than 8K miles ago... Quote Link to comment Share on other sites More sharing options...
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