'99 2WD, which Cat Converter?
 

Hi everyone (that reads this),

Wife has a '99 Blazer with around 180K miles. In diagnosing a P0420, I assume the Cat is bad since all 3 O2 sensors are giving readings from .2XX to .8XX. ODB II tells me there are 3 sensors.

Two questions:

1. Which Cat do I buy, the 4 on Rockauto don't tell me enough for a determination. We live in TN.
2. Could the issue actually be the O2 sensors. If possible, then I'll take to a shop for a "professional diagnosis". Certain they've never been replaced.

Engine runs around 193° in 36° weather 3 days ago.

Thanks in advance.
Robb

Catalytic convertor
 

Looking at the ones on Rockauto, it looks like 3 of the 4 are the direct fit Cat's, and should work. I just replaced mine in my 98 and used the walker model and fit perfect, I also got a $40 rebate, not sure how long that deal is running.
The Eastern model # 50361 is for California emissions vehicles. Not sure of the history of your vehicle, but if you're in TN, and the Blazer was originally from that area, then you should be ok with any of those 3 models. Good luck!

are you worried about how hot it ran when it was that cold out? in the manual it should tell you that the thermostat starts to open at 195. the engine in more efficient when its hot. if it starts running cold, like down around 120 or so, your thermostat is probably failing and isn't closing. but, its better that it fails in the open position than in the closed position, at least it wont over heat under normal driving.

Not concerned at all with the temp, juts sharing the information that it runs hot enough. in the newer TB forum, cats go bad when the engine is not heating enough.

thanks for the input, guys!