I got the following codes from my check engine light:
P1276 APP Sensor 1 CKT Performance
P0440 Evaporative Emissions System Fault

I cleared the codes and nothing came back up. What could the problem have been.



Also, what are O2 readings suppose to be? I got teh following:
O2 B1-S1 78-759
O2 B2-S2 82-829
O2-S2 243-833
Are those the ranges that they are suppose to be in?

 

Before you get too far. I found when I got bad readings on my 98 3800 o2 sensors b1 and b2 that alot of people had the same issue. I replaced mine about 3 times and gave up because the codes would come back in a month. I droped my Y pipe to change my plugs and broke a bolt. The car was loud but after a year of driving around with my check engine light the light went out driving around after the back pressue released. If I remember correctly The 3rd O2 sensor is in front of that Cat also. The O2 Bank 1 and Bank 2 are directly on the header and excruciating to get to. At least on the Passenger side.

You could disconnect in front of the cat disconnect the battery negative terminal for a minute and reconnect it. Make sure the SES light is gone. run the car for a bit on the ramps or jack stands, and see if your light stays out with the rear exhaust disconnected. If it does then I would think all 3 sensors went good and the cat is your problem. Please feel free to correct me if Im wrong. I really think that the cat may be the common issue, not the 02 sensors...

Dont leave it disconnected while driving, or youll gass yourself... I know some mechanic is reading this beating his forehead but I found out the hardway.