I had an oil and filter change, brake pads and shoes, brake cylinders, and an oil pressure switch done today. Two hours after I got it back the Service Engine Soon light came on, and has stayed on. Could this be related to the work that was done? If so, how? If not, what could it mean? Thank you for any help!

It sounds like the oil pressure switch may have triggered something.

I would take it in to Auto Zone and have a technician do a free reading of your check engine code to see what it going on. They can point you in the general direction of the problem and you can take the print out to your mechanic.

My 1997 Tracer was giving alot of check engine errors this year and itended up beinga progressive problem with emissions. Every time I would get one part replaced that helped clean emissions, another one would fail. I think it was a syndrome of flushing out some "dirtiness" somehow. I replaced almost any part related to the EGR and got all new vacuum lines (as the originals were rotting).

I have a feeling this might be what is going on with yours?