You would hope that anyone who could hook up the scan tool, could read codes , that would indicate a faulty sensor.
I'm scratching my head for a sensor that would set both ; check engine and trans warning;
TPS, has a redundant feature and should only set check engine, if 1/2 goes south, if the TPS fails completely you should still be able to shift. Engine RPM, sensor, is shared info between the engine and trans.
Was the tach, working properly ?
If trans controller thinks RPM is too high, it won't shift.