...
When the PCM sees any discrepancy whatsoever between the signals of the commanding TP sensors on the accelerator pedal and the commanded signals of the TP on the throttle body, it will go into failure management, shut down the ETC system, set "ETC Failure-Throttle Limit" codes, and display "ETC FAILSAFE" on the message center. This usually doesn't result in the car shutting down, as Mindymark pointed out. The engine will continue to run, but will be locked at idle RPM; there will be no response to the pedal.
If this is what's happening, and the dealership is recieving codes P2106 and/or P2135, there's a TSB for that!!!
Ford Technical Service Bulletin #05-14-04 calls for the replacing of the throttle body TPS with redesigned part, #3L5Z-9B989-AA.
...