What P0709 usually means
P0709 means the PRNDL input is not dead all the time; it is unstable. That is why this code can be especially frustrating. The transmission may behave perfectly on one drive and slam into fail-safe on the next because a loose connector, vibration-sensitive wire, or worn selector contact opens only occasionally. The key is to treat it like an intermittent signal problem first, not like a guaranteed internal transmission failure.