I had a coil problem which I've now fixed. With the original miss I had the SES light come on and once AutoZone pulled my codes, had P1343 (Cyl 1 misfire) and P0161 codes. Replaced Cyl 1 coil and no more miss so yesterday had my buddy clear my codes and reset the light so it was off. After driving for a short time the light is back on so took it to AutoZone again and the P0161 code is back. The P0161 code says Bank 2 Sensor 2 sensor heater circuit open or short circuit condition. Most times when you have that code is the O2 sensor bad? Is there a way to test one? Also where is it physically located on a 2000 540iA Wagon? I looked through the online service manual and couldn't find info on that.