I have a 02 GTP and I threw a code today. I got my car scanned and it came up as a P1133 code. It indicated that I had insufficent switching of my fuel ratio. Also said probable cause are: heater circuit, shorted ECM ground, and improper oxygen to sensor. ANY HELP WHERE TO START???????? I have never heard of this but the car seems to be running fine. I dunno what to do and I can really use some help to figure out why it threw the code! Thanks for your guys help I really appreciate it.

Erick