I changed my upper O2 sensor on Monday and since then I keep having a error code come up that deals with the heater warm up is below effiency. I have cleared the code 3 or 4 times and I have disconnected the battery for a few hours and then drove the car and the CEL was off, then I drove the car to work tonight and the CEL came back on. Am I doing something wrong or is the new sensor messed up. I am at a loss. Please Help.