Hey yall new to the forum. I have a question. I have a 2000 Chevy blazer 4.3l vortec. I am having a dtc code of p0420. Which is catalyst system low efficiency bank 1. I have what it sounds like a rattling comong from the tail pipe. And runs rich where i can smell gas in the cab. I crawled under the truck today and found out that there is no cat. They just cut it out and welded in a slip joint as long as the cat. Any suggestions??

 

Welcome to the forum!


Running rich is most likely what destroyed the converter. The rich condition needs to be taken care of before a new converter is installed or it will be destroyed as well. This link explains how to test the fuel delivery system: https://blazerforum.com/forum/2nd-ge...eakdown-88305/


If that checks out OK, the ignition system is the next thing to check.

 

That would be the post cat o2 sensor causing the issue due to the cat not being there, or if the sensor is there it believes the cat is bad.

2 choices, replace the cat, or search for "o2 non fouler" trick

I recommend a Magnaflow direct fit converter, it replaces the pipe from the manifolds back to the muffler flange, and it flows very well. Best part is you dont have to take it to a muffler shop and have it welded in, you can do it in your driveway in a couple of hours with a few hand tools. I put these on all my blazers, 2 so far, and I am about to do a third. You can usually find them for under $220 shipped. Check Magnaflow's site to find the part # for your application.