Hey i have a hummer h2 2004 and i have the check engine ligh on the code is p0135 (bank 1, sensor1) what sensor is it? thanks

Hello: Bank 1 tells you it is the side of the engine that has #1 cylinder (Which on your truck is the drivers side) SENSOR 1 IS THE SENSOR FOR THAT BANK IN FRONT OF THE CATALYTIC CONVERTER. This code tells us the heater in the sensor has a problem. You should replace the sensor. (Experience: I highly recommend a GM part. The GM engine control module is very sensitive to 02 sensors). Make sure the truck end of the harness connector is clean and not damaged. After replacing sensor you will have to have the code cleared. (auto Zone, Advance Auto may can do it and not charge you.

This is the oxygen sensor that is screwed into the exhaust. Bank 1 means that it is on the same side as cylinder #1. Sensor 1 means that it is before the catalytic converter not after. Generally when you get an O2 sensor code, it is usually not the oxygen sensor itself but something else causing it to read rich or lean. However, this particular code is for the heater circuit within that sensor. This is a confirmed kill, replace that sensor.