Volvo Repair: P0171 CODE, vacuum leaks, voltage spike

Question
HI@I HAVE 2002 S40 AND CODEP0171 CAME UP IS THIS FOR A O2 SENSER TO BE REPLASE I HAVE 104000 MILS ON

Answer
   Mike, first check for vacuum leaks. Then check and make sure the EGR system is not stuck open. You could have an air mass sensor problem, but unlikely.
   If you have the ability, hook up a labscope to the 02 output and see what the activity is and how fast it's switching. Try injecting carb cleaner ito the intake while running and you should see the voltage spike. If no change, replace sensor.

Merry Christmas

Mark