Toyota Repair: 1996 Geo Prizm P0125 code, 1996 geo prizm, geo prizm

Question
Hello. I have just bought a 1996 Geo Prizm with its check engine light on. AutoZone tested it and said the OBD code is P0125. I have tried to look around and it seems like this is a problem with the Coolant Temp Sensor. Then other places I have looked make me think I need to replace the Oxygen sensor.  

Which is it? Is it something else entirely?  If it is one (or both) of these sensors... Where in the car are they exactly for me to replace them? After repair... should the check engine light just come off by itself after that?

Thanks so much in advance.

Kathy

Answer
Replace the O2 sensor, the #1 sensor located in front of the catalityc converter, the water temp sensor is not causing the problem. The check engine light can be turned off by disconnecting the negative terminal of the battery, wait ten seconds and reconnect it.