Throttle sensor error code 12
 

I have an S5 convertible, 91. My TPS lower plunger started sticking so I swapped it out for one on my friends S5. I pulled the error codes off the ecu, and it came back 12, 13, and 27. 12 is the TPS, 13 is the pressure sensor, and 27 is the MOP. I got kinda worried, so I reset the ecu to see if they had been fixed or not. I hooked it back up, and pulled the codes again. Error 12 came up again. The plunger is acting as it should, although the idle fluctuates for 800 to 900 rpm for a sec, then levels out at 800. What could be causing the error code to come up after I put the new TPS in? Any info would be greatly appreciated. Thanks Guys, and Happy Rexin'!!!!

Maybe a bad TPS. Check for spikes in the resistance. If the car runs fine than I wouldn't worry about it even if it is bad:)