Catalytic Converter...

[mijohnst]

Just when I think I'm at the end, something else happens. I started getting the P0430 error about a week ago. Engine seems to be running like a champ after I fix the oil pressure sensor. The engine doesn't sound funny or have any loss of power. I've changed out the downstream O2 sensor on bank 2 back in December. From what I'm reading, I should change out the upstream sensor before switching out the catalytic converter. I guess I can do that, but I feel like it's going to be a waste of time.

Any high recommendations from one off RockAuto or Summit? I've seen some pretty cheap ones on Amazon, but I'd rather just get it done the right way. Looking for recommendations on what I should buy. Also, should I go ahead and change out the muffler while I'm at?

 

[OR VietVet]

If you are going to change out sensors then do Bank 1 downstream sensor. Get a back pressure test done on the cats. Typically the upstream sensor is not gonna set this code. The code has to do with the cats performance and that is read by the downstream sensors. Stand by though, you know another shoe will drop after this repair.

https://www.rockauto.com/en/moreinfo.php?pk=388841&cc=1380372&jsn=2247

The muffler bolts to the back of the cat y-pipe assembly. No need for that muffler if not needed. I would get in there asap and start spraying the bolts at the front and back with your favorite penetrant. This is best I ever used.

https://www.amazon.com/Kano-Aerokroil-Penetrating-aerosol-AEROKROIL/dp/B000F09CEA

 

[mijohnst]

Ron, I love the advice yet again! I just finished putting 2 orders in and I'll start hitting those screws as you recommend by the weekend. I won't get the replacement converters until the next week so I've got time. Thanks again!

 

[THX1138]

I have a 2003 Tahoe LT with 177K.
Received the same o2 sensor codes. Replaced the downstream on bank 2 and it still thru a code. Replaced the upstream on Bank 2 and still thru a code. Took it to another mechanic and they read a bad CAT. Replaced the CATS with a Flowmaster CAT from JEGS.com as well as a new Flowmaster muffler. Codes went away and I kept the old O2 sensors in case I need them again. The bad CATS were causing the O2 sensors to code.

Good Luck

 

[OR VietVet]

Do the penetrant 2 times a day till the work starts or when you know the bolts/nuts are moving freely. When you are working with a through bolt and a nut that is not as critical because that is easily replaced with new. Working on a stud that has a nut on it is more critical when it comes to breaking loose and unthreading. I like to use the penetrant and when I am ready I will actually try tightening the nut a little or if it is a bolt threading in to a captured nut I tighten it a bit too. I like to break it loose by tightening it first. Then I move slowly as I unthread till I can see it will move freely and just take it apart. I have ran across some that fought coming apart the whole way. I have taken up to 15 minutes doing that before. Then when apart and if I am reusing the bolt or nut I clean and lube all threads thoroughly before reassembly. Get the other O2 sensor for downstream bank 1 and replace with the cat system if you are doing that.

If you can afford it and the front sensors are old, do them too. But from the code the only ones to worry about are the downstream sensors for now if you need to wait. If you plan to reuse the upstream sensors use the penetrant on them where they thread in as well.

 

[mijohnst]

I have a 2003 Tahoe LT with 177K.
Received the same o2 sensor codes. Replaced the downstream on bank 2 and it still thru a code. Replaced the upstream on Bank 2 and still thru a code. Took it to another mechanic and they read a bad CAT. Replaced the CATS with a Flowmaster CAT from JEGS.com as well as a new Flowmaster muffler. Codes went away and I kept the old O2 sensors in case I need them again. The bad CATS were causing the O2 sensors to code.

Good Luck

Was installing that Flowmaster muffler a big deal? I'm looking for a youtube but haven't found any installs howtos yet. That either means I need to take it somewhere for welding or it's so easy that nobody would need to make a how-to for it.

 

[mijohnst]

Do the penetrant 2 times a day till the work starts or when you know the bolts/nuts are moving freely. When you are working with a through bolt and a nut that is not as critical because that is easily replaced with new. Working on a stud that has a nut on it is more critical when it comes to breaking loose and unthreading. I like to use the penetrant and when I am ready I will actually try tightening the nut a little or if it is a bolt threading in to a captured nut I tighten it a bit too. I like to break it loose by tightening it first. Then I move slowly as I unthread till I can see it will move freely and just take it apart. I have ran across some that fought coming apart the whole way. I have taken up to 15 minutes doing that before. Then when apart and if I am reusing the bolt or nut I clean and lube all threads thoroughly before reassembly. Get the other O2 sensor for downstream bank 1 and replace with the cat system if you are doing that.

If you can afford it and the front sensors are old, do them too. But from the code the only ones to worry about are the downstream sensors for now if you need to wait. If you plan to reuse the upstream sensors use the penetrant on them where they thread in as well.

Great advice, thank you! I'm going to get it on stands this weekend and hit those nuts and bolts before and after work until those converters arrive. I also ordered all new bolts, nuts, and studs for the job. And because I don't want to do this again for a long time, I bought 3 new OEM O2 sensors to replace the other 3 that I hadn't replaced yet. I'm actually kind of looking forward to it.

 

[drakon543]

doing a muffler swap can be done cheap and easy and well or cheapish slightly harder and really well. anything outside of that and you wasted your time. measure the distance you need to take up between the tailpipe and the pipe before the muffler. pick a muffler you like the sound of and get the overall measurements of length. buy an extension pipe of the appropriate length so the muffler plus whatever you need of the extension pipe will fit. you will also want 3 band style exhaust clamps. also make sure all of those items are purchased with the correct diameter to match your current pipe. and your done with cheap diy properly. slightly better and slightly harder diy would be to replace the mid pipe and tailpipe at the same time. band clamps still fit the bill unless you know someone with 309ss welding then possibly welding it all together so it never moves on you and the 309 ss will last a while at the joints and keep the joints sealed better.

 

[Wylie_Tahoe]

If you have a post converter o2 efficiency code and no pre-converter o2 codes, odds are, its the converter or the sensor.

 

[ks03]

What’s the logic behind changing the bank 1 downstream o2 sensor for a p0430?
Even if you mean bank 2 downstream, 420 and 430 codes set for too much activity (switching like the upstream sensors).