Hello, I have a 99 S70 non-turbo (92,000 miles) which has just recently started illuminating the CEL. When I hooked upmy code reader, I got P0130 (O2 Sensor Circuit Malfunction Bank 1 Sensor 1)and P0136 (O2 Sensor Circuit Malfunction Bank 1 Sensor 2). I was wondering what I should check/test before I go ahead and replace both O2 sensors. I checked for vacuum leaks yesterday and founda disconnected hose, which I reconnected. After clearing the code and test driving, the light came back with the same codes. How do I go about testing other possible problems (such as fuel pressure)? Thanks a lot.

 

You would need a get a fuel pressure guage and connect to the fuel rail.
But if they come back that fast it is usually bad sensors.