I got a P0135 02 heater circuit trouble code (bank 1, sensor 1) on my 2001 Silverado with a 5.3 V8. The truck has Pacesetter long tubes and ORY. It has a proper custom performance tune.

So, does that simply mean I need to replace the upstream O2 sensor for bank 1? It mentioned something about fixing a short on the harness as the only other possible solution. I havent' crawled under the truck as of yet, but i'm pretty sure the wires were safely tucked away during header installation.

One thing about it. The only symptom associated with this trouble code is bad fuel economy. And let me tell you, that is no lie. My fuel economy is horrible all the sudden.