transmission repair and my check engine light?

After a transmission repair the check engine light came on when the car was cruising at 65-70 mph after a pretty consistent period, I could drive locally @ 55 mph, with the car getting warm without any check engine light. Each time the mechanic checked it was an O2 sensor issue, both front O2 sensors were changed, the computer reset and again the light was on at the same area of the highway. The problem is with each recheck of the code it often bounces back and forth between those two front sensors. Could a wire have been effected when the transmission was repaired? My gas mileage and the car's performance are fine. I can't get my car inspected with the check engine light on and I would hate to miss something else going on with the car because of the light being on constantly.