XC70 B5254 t2 2003 in limp mode
 

Hi, my XC70 faltered on start up recently and came up with the warning triangle and message “Reduced engine power” I borrowed a code reader and it gave me P2111 throttle stuck open. After some research I removed the throttle body and cleaned it out and reinstalled. The battery had been disconnected during this operation and when connected up after everything in place the code had gone and the car ran perfectly. However the next time I started up the fault returned. I guessed that the position sensor may be faulty so I sent it to ECU Testing Ltd for repair, but it came back with no fault found.
Where do I go from here? I have not reinstalled the throttle body in case I have to check wiring etc, but where to start and what to check?
I would appreciate the benefit of your knowledge on this as it has me stumped.