Throwing P0430?

[SVT Tyler]

Hey guys just trying to get some input. First off i have Mac longtubes, offroad x, and a catback ( yes i have MIL's) The first code i threw was a oxygen sensor malfunction (P0136). So what i did to just test is clear the code and see if it would come back. I also switched MIL's frome each side to see maybe if it was those. So P0136 came on after about 40 miles of driving so i bought a new oem oxygen sensor. Now after installing the new sensor i get P0430. Catalyst efficiency? I have the MIL's in. So im thinking its either bad MIL's or and exhaust leak. Looked under the car last night and saw my muffler slightly backed off the pipe that connects into the x pipe and yes it had black around where the clamp was so which leads me that i have and exhaust leak. Now my question is would P0430 be caused after the "cat" and oxygen sensor where i think my leak is? Couldnt find any leaks on that bank besides the one i found, the longtubes are clean as a whistle. Thanks guys

 

[iamtheshaner]

My vote is bad MIL elminators. The P0430 means that the switch rate of the downstream 02 sensor is too frequent in comparison to the upstream. If the catalyst is working ideally, the downstream sensor signal does not switch between high and low voltage at all - it's a flatline. Naturally, if you have no cats the upstream and downstream signals will be identical. So....sounds like the MIL is not generating this false .7v signal but rather allowing the sensor to send it's TRUE signal, which reflects the absence of a working catalyst.

 

[SVT Tyler]

Thanks for the answer!

 

[SVT Tyler]

Forgot to mention. I had my offroad x and catback on and this code never came on. Once i put the longtubes on this year it been happening

 

[iamtheshaner]

Longtubes mess with upstream 02 switchrate. Because the sensor is located further back, there is a longer delay between when the PCM commands a fuel adjustment and when that change is seen.

Either way I'm positive the P0430 (and P0420 for that matter) indicate an issue with the downstream sensor switchrate.

 

[SVT Tyler]

So where should i go from here?

 

[iamtheshaner]

It would be nice if you could datalog or at least backprobe the bank two downstream 02 signal to see what the voltage is doing. Based on the code I'm guessing it's doing the same thing as the upstream bank two 02 sensor (switching between around .1v and .9v.....

But without this information, the best suggesting I can think of is to swap the MIL eliminators side to side and see if you set a P0420 after a day or two. This would indicate a bad MIL elminator.

The bottom line is that the P0420 and P0430 codes mean the catalyst isn't working. If you have an O/R midpipe (without cats) these codes SHOULD be set; hence the need for MIL elminators when running these parts.

I wouldn't put too much stock in the fact that the codes didn't set until some time after you installed the longtubes. Coincidental

 

[SVT Tyler]

American muscle is sending me new mil's at no charge and im going to put another rear o2 in since i replaced the other one. thanks for your help! Hopefully this will solve it!

 

[SVT Tyler]

New MIL put in within 6 miles its the same code that popped up. I guess now its time for a handheld tuner?

 

[iamtheshaner]

Is the P0430 the ONLY code you are setting?

Either get a scan tool on it or backprobe the downstream bank two sensor signal circuit to look at voltages.... I'd like to know if the downstream is switching; especially with the MIL eliminator in it.

 

[Zemedici]

I'm getting the same code, and I have MILs too...

 

[SVT Tyler]

Yes its the only code im setting

 

[Zemedici]

i've read the MILs malfunction rather easily when water gets in them, this week I'm going to take mine off, clean them out with brake cleaner/electrical cleaner, and put die-electric grease in them to try to ward away water in the future. Hopefully this fixes it..

 

[SVT Tyler]

my car has never seen water lol...idk what the hell to do. i guess my buddy will just tune them out so i can pass emissions. They say o2 spacers work but i have a feeling they wont for me

 

[Zemedici]

Yeah i dont want to spend any more money unless its guaranteed to work, so i'll just have my car tuned I supposed, while i'm at it i may as well pulley it up.

 

[LilBerx]

I get the same code, I just clear it with my tuner. I have had my car dyno tuned twice, it's thrown it ever since I swapped a o/r x pipe on...

 

[OneSicMystic]

Hello there. I just got my eliminators from UPR and I'm getting the same p0430. I'm going to check it again with my scanner later today to see if the one is switching. I'll update later. I have UPR off road X pipe new on the car too. Factory headers though

 

[iamtheshaner]

I know the MIL elminators don't work on "newer" OBD2 systems because the PCM will check the oxygen storage ability of the cats by forcing the mixture rich then lean for a long period of time...usually when idling. Late 90's cars aren't this "smart" usually and I know the MIL elminators have worked on these cars for years.... wish I could see a datalog of what's going on here!

 

[OneSicMystic]

Do the spark plug anti foulers really work? I found a sticky on here about it. I'm grabbing a set tomorrow to install and I'll let u know how it turns out. I emailed UPR about one of my mils not working and haven't gotten a response back. Supposed to be a warranty on them. I just wanna get that pesky light out because I've been dealing with imrc issues and would like to know when they're faulting

 

[SVT Tyler]

did angled cel fix (o2 spacer) from big daddies garage. 30 miles and no light yet!