Display shows error 51
Possible cause(s): Improper accelerator pedal linkage, faulty accelerator sensor, faulty main harness, faulty logic unit.

How the error code is triggered:
Accelerator sensor voltage is out of range of 0.2v to 4.8v.
Sensor voltage is 1.41v or more when accelerator switch is opened
Sensor voltage is 0.3v or less when accelerator switch is closed

So either your accelerator linkage on the pedal has moved causing the sensor to go out of range or the sensor itself has a bad spot it's wiper causing the voltage to fluctuate out of range triggering the error. Could also be damaged wires on the harness.

All of the above also applies to the EX models as well ;o)

Good luck