Hello everyone. I have a 1999 S70 with 78,000 miles. Several weeks ago my check engine light went on during a bitterly cold visit to the mountains for skiing. Upon my return, it went out. Since that time, it has been going on and off. I borrowed an OBDII scanner and I received code P0130: Sensor circuit Failure, Bank 1 Sensor 1.

I've poked around the archives a bit and it appears that I should check the voltage reading of the sensor to make certain that it fluctuates normally. Also, someone mentioned checking the sensor heater resistance. I'd be happy to do this but exactly where is this sensor or it's leads located. Also, I understand that other malfunctions could result in this error message. Any thoughts appreciated. Hopefully I don't have to replace what appears to be a $150 item.