Intermittent transmission issue goes into limp mode at 25 or at 40 mph? causes?

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Started very infrequently car won't accelerate over 25 or 40, if you pull over and turn it off and back on often it would go back to working just fine. Now it's happening most of the time. Check engine light does not come on. Error code state that it is accelerator position sensor. P0698, P2122 or 2121? dealership want overs 800 for the part?