No luck with Jackaroo TPS

Removed throttle position switch, pulled it apart and cleaned thoroughly with Isopropyl alcohol. It was, however, very clean, just a small amount of carbon dust on the cylinder shaped internal core. I can't see how any oil contamination in the air supply could get into the switch because it is exterior to the throttle body and the only connection is via the spindle of the throttle butterfly. This is assuming I cleaned the right component - it comprised a black cylinder which connects to the throttle butterfly spindle, the cylinder rotates inside a round metal housing which obviously has some electronic sensors embedded in it to indicate the position of the cylinder and hence the throttle butterfly.
I took off the hose between the intercooler and the throttle body and could see that the inside of the throttle body and the butterfly were very dirty, all components covered with a black oily layer. Is this normal or is there something wrong here?
Anyway, cleaned everything, put it back together and.......check engine light comes on and stays on. I tried disconnecting the battery for a while hoping it may "reset" the diagnostics but still no luck. Looks like I'm back to the dealer?