Good Morning, My 2007 Volvo S60 2.5t has a consistent surge when idling, its similar to when my ETM was messed up and it would sway the RPMs up and down, except this time it just surges and the RPM's stay as is.
I got a tune up, and had the throttle body and everything cleaned and it is still surging. The Check engine light came on and says there is a problem with the O2 sensor.
Basically, could the O2 sensor be the problem?
any ideas?
Thank you for your time.

 

What is the code? A code for an oxygen sensor does not always mean the sensor is bad. A vacuum leak will cause surging RPMs and also set oxygen sensor codes.