The check engine light on my 1997 Disco I (180K miles) came on and AutoZone read this code from it. The truck was recently into the shop for an oil change and had one of the post-cat O2 sensors replaced. The guys at the shop also tightened up a very loose exhaust.

Are there any common issues or failures that lead to this code?

Thanks!!

 

Well you need to have all of your O2's repalced at the same time. Or at the very least in pairs, so the back two and then the front two for example.
A poor tune up will set off O2 codes but that code is for a bad catalist, meaning a bad cat. If that is the case then you need to replace both cats at the same time.
But replace the other O2 first and go from there.

 

At your mileage, and not knowing the engines history, I would say it is time to swap out both cats to get back up to where you need to be.
Local muffler shops can replace them cheaply.

 

Thanks a lot for the quick replies gentlemen, I am heading to the shop at lunch to have them give it a look.

My hope is that replacing the additional O2 sensor will fix the issue. I'll post their diagnosis in here as I imagine you are all perched on the edge of your collective seats. One point I forgot to mention was that the truck does have an aftermarket exhaust, although I am not sure of the mileage at which it was installed.

 

It looks like the cat is bad. My local LR mechanic referred me to a muffler shop that can replace both of the cats for $450. Does this sound like a fair price to you experts out there?

 

Just so that you can compare.
http://www.roverparts.com/Parts/ESR4106.cfm
Are they going to replace the y-pipe too?

 

Thanks Spike. I believe the price they quoted me was inclusive of the Y-pipe, but I will confirm. I trust the mechanic that sent me to this shop so I don't think they are going to work me but I wanted to be sure.

Should the Y-pipe typically be replaced when doing the cats?

 

Well yes and no. The cats take up 80% of the y-pipe, but if it aint broke dont fix it, but yet you will be welding new into old, I would replace it if you can afford it, if you cannot afford it then just do the cats.
If they are going to replace the whole thing then hell yeah, that is a good price and go for it.

 

You can get 2 cats replaced for alot less then that, shop around.
Why didn't you replace all 4 02's, with that mileage they all should have been replaced to improve your performance.

 

The replacement of just the one was at the advice of my mechanic. I would assume that the others have been replaced at some point but you've sparked my curiosity. Is there a way of testing the other O2 sensors?