Where is it on the truck 2003 blazer 02sensor heater circuit malfunction bank 1 sensor 2?

Answer 1

The bank 1 sensor 2 O2 sensor on that vehicle should be the sensor after the catalytic converter. Inspect the wiring for damage, cuts and such, if the wiring looks okay it is probably the heater circuit within the sensor, replace the sensor. Unplug the wire harness from the sensor and cut the wires off at the sensor. This will allow you to slip a 7/8" box wrench over the sensor to remove it. Install the new sensor using a 7/8" open end wrench, tighten it as you would a spark plug. Reconnect the wire harness.