Question about the check engine light - took it to a mechanic when the light came on (because I had been trying to sell it) - said the code coming back was that there was a bad AIR pump, so it was replaced to the tune of about 500 bucks. Agreed to sell the car to my brother-in-law, and then the light came on again. Took it to a different mechanic (had been living in ATL for the summer and now have returned home) who said the same code (P0140) was coming up again.

So the first question is: what else might be the problem, knowing that the AIR pump is new?

Second question, is there any way to tell whether or not the return of the check engine light was the first mechanic's problem (it came on around 3 weeks after the original repair)?

Third and final question: could my brother-in-law do the work himself? (he's got some mechanical experience, but new to volvos)

Ya'll are awesome.