Think cats are clogged need opinions.

[Bigshawn]

My 01 yukon 5.3 has 334,000 miles and P0430 and P0420 codes are both coming up but it doesn't feel like they are clogged. I've ran some techron and cataclean thru it about 10k miles ago but didn't help with codes. I'm afraid of dumping to much money into it with the miles that are on it but it's still running strong. I looked on rockauto and can get new cats plus the 4 o2 sensors for like 300 to 400. What do you guys think? @Tonyrodz always value your opinion

 

[OR VietVet]

IMO, the codes may be related to the sensors and I would do all 4 of them first. How old are the existing sensors? Do yourself a favor and use GM or Delphi sensors.

 

[exp500]

And a Vacuum gage on a test drive will verify Cats.

 

[Fless]

Have you looked at the graphs of the O₂ sensors' activity? I would agree with @PNW VietVet to check and/or replace those first.

How about fuel trims, short- and long-term; have those been looked at? The upstream (front) O₂ sensors will drive the fuel trims. The downstream (rear) ones will drive the cat efficiency codes.

 

[George B]

I have been down this road before. I ended up doing a parts shotgun. Four sensors and new cats got me another 100k on a 2003 Burb. That is from 156k to 256k before I traded it off.

 

[Fless]

It would be best, from my point of view, to do some diagnostics to confirm before you spend the $$ on cats. O₂ sensors are somewhat a wear item and will likely need to be replaced at some point, anyway. To each his own, though.

 

[George B]

I should add that I agree with @Fless and @PNW VietVet about diagnostics. I did a fair share of checking how the cats were performing prior to biting the bullet.

 

[Bigshawn]

@PNW VietVet they are still the stock o2 sensors and @Fless yeah i have been keeping a eye on them. The 2 front ones work ok but the 2 downstream quit reading. One of them was like 8 months ago and the other just quit like 2 months ago but if I remember right the one would work here and there but it just mimicked whatever the front one would say. I know that means something just can't remember lol. I got like 25k saved to get a newer vehicle but I want to get everything out of this one and I got alot of new parts on her. I forgot to say earlier p0401 code just started coming up to which is egr insufficient flow. That's kind of what was making me think the cats and o2 sensors maybe are both going out.

 

[OR VietVet]

Again, IMO, at the minimum replace all 4 sensors with quality parts. If they are the original sensors, they are way past due for replacement.

 

[Bigshawn]

Sorry my Wifi is acting up, man it ****** me off. Ltft on both sides usually runs between 5 and 8.