99' Blazer-engine code P0420
 

Hello, I have a 1999 Chevy Blazer and lately have had some problems. The truck just dies after you drive about 20 miles (this only happens when its hot outside), so i am guessing it is probably over heating. I took it to get checked out because the engine light came on and they gave me the code P0420 which is the catalytic converter. But they also told me it might just be the O2 sensors. Does anyone else have this problem or maybe some advice, i am not too sure where to start and don't want to replace anything that doesn't need to be replaced. Any help would be greatly appreciated, thanks!

stalls while hot
 

I don't think your p0420 is related to the stalls...

I was mystified by this problem since I got my blazer in january. I finally broke down and dropped some green to try a new coil ($30) and ignition control module ($65). Seems to have fixed my problem on a 97.

After I popped the rivets on my ICM, I found the thermal grease was dried into a crusty mess. I'm thinking maybe the heat sink just wasn't dissipating heat as it was designed to. I probably could have tried re-using the old ICM with a fresh layer of heatsink compound, but I opted to swap it out with the new one.

You'll need some small hardware to put your original ICM back on if you don't buy a new one that comes with bolts. I'd say it's worth a try for a few dollars of heat sink compound...