Code C20 - Thumb Control Warning
Reason-->Thumb control was not in neutral position at power ON, or a throttle position sensor failure was detected
Possible Causes and Corrective Actions--> Thumb control is stuck in drive position.
ETAC is bad.
Check the mechanical portions of the throttle controller. Give special
attention to the magnet arm alignment with the ETAC sensors and to the
non-metallic parts of the emergency reverser