Just finished doing all sorts of work to volvo and just replaced another defective front O2 sensor by Bosch. Now a day or so later I get another check engine light on and the code this time in A2 was a 315 -EVAP System. What could be the problem here and what should most likely get replaced? Car has 259K miles on it at this point.

I hate these general codes. Check the vacuum lines around the vacuum canister, and check the canister for cracks. One of the check valves may also be broken.

If you over fill the gas tank while at the pump, this also dumps gasoline into the canister and fills it up.

If you are in an emmissions testing state, clear the ccode just befor you get tested :) It has no effect on drivibility or engine performance.

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)

I had 3-1-5 returning after every 500-600 miles. I checked all the lines, the canister, and the valve (somewhere there is a procedure that describes how to do it), and everything passed.

Around this time, my fuel regulator because I had long turn-over times before starting. Per Klaus, I replaced the regulator. Miraculously the 3-1-5 went away for good. Related? I don't know.

Don '95 854T with 178K miles at fuel regulator replacement.

I replaced my fuel regulator switch about 2K miles ago, replacing the original unit on the car.

Is there step by step pics of this canister thing. Also wondering where I can get new one online.

Thanks.

You can get a 'new' one from a salvage yard, just make sure it isn't filled with water. The cannister is on the driver's side on top of the subframe in front of the wheel.

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)