error code is P0141 Bank1 Sensor2. came back on

I went and got a emissions test and I failed:banghead: becasue the check engine light came on and the error code read P0141 Bank1 Sensor2. So I went to the auto store and bought a a downstream O2 Sensor and had a mechanic install it and turn the light off and a hour later it came back on can anyone please help!:banghead:

did the code get erased after he installed the part?

The mechanic used the computer to erase the check engine light and afyter about a hour of running it came back on

P0141 indicates a problem with the heater circuit, it does not say replace the sensor. Diagnostics for P0141 include checking the fuse, and the wiring to the sensor. Ignition in RUN position, heater wire must show battery voltage. The ground wire must show less than 5 ohms resistance to ground. Post your results and we can continue if necessary.

I agree with old master that the circuit needs to be checked. Another possibility is the new sensor has a bad heater circuit (especially if you bought a Bosch branded sensor, they are infamous for heater circuit issues).

Is there anyway I could this myself and if not about how much would it cost to fix the prolem if it is what u said

Maybe I missed it, but what year, make, model, engine, please ?

05 cavalier 2.2 4 cyl

You can check for battery voltage at the heater(O2 sensor), brown-pink wire.
If good then check ground wire, black wire.

As far as cost of having a shop do it ? Depends on how long it takes to find the problem and how fair minded the shop is.