I got a read at Autozone, got DTC P0420 for my 98 Silverado K1500, 5.7L. Can anyone help me with this? Is it going to be a new catalytic converter? Thanks. J

 

could also be a bad O2 sensor after the cat, might also check for any exhaust leaks before the cat...

 

Got your input, in2pro, thanks for that. Some background: just before the code reading ceremony, I replaced the 3 O2 sensors. Expensive, but I believe in replacing them as long term maintenance anyway. The read, I've had 2 code checks, gives me high voltage output as well. P0350 or something. Well, I'll replace the ICM and coil sometime soon as more maintenance. I fixed six exhaust leaks when I bought the truck in January, and there are no leaks. I think I'll be exchanging the cat soon, also maintenance. My 5.7 does not consume any oil between changes on a 3 month timeframe. Doesn't overheat, runs great, got 18mpg on a 500 mile trip towing my light boat. So it's in pretty good shape overall. I'm not that familiar with the catatylic converter personality, so if you have any information for me that would help a lot. Or anyone in the forum, for that matter. Thanks. Jim