Volvo Repair: Check Engine Light, wheel bearing, flame trap

Question
My 1998 S90 check engine light came on. The diagnosis was faulty fuel cap. I cleared the code and installed new gas cap but the light came back on after a couple of days. Can you help? Also, with 56,000 miles I am told it has a bad rear wheel bearing, what causes the wheel bearing to go bad and is it problematic with the S90?

Answer
Hello Bill,  Fuel cap codes are somtimes taken for granted,there is also a small hose at the 'evap'box that splits.Its under the rear area,left of the driveshaft.Presumeing the 2nd codes were same as 1st.The 960 also has  a 'flame trap hose' breather sys. and that can get clogged and set off the ch.eng.lite.As for the wheel bearing they are not problematic on these model any more than other rear drive cars.Curb hits in the snow or mud that don't appear serious,can show up later in life.Bearing are of the 'two half,pressed ball'type,heat and shock are the natural enemy.Heat builds due to'out of alingment',after a 'bottoming out' or' good pothole' hit.Lastly is age and enviroment,sun belt/rust belt.Metal is, after all only metal.Thank you and good hunting!  PKD