An error code P1684 from an OBDII code reader indicates that the battery had recently been disconnected. This is normal if a new battery was installed but can indicate a connection issue or grounding problem.
Trouble code P0780 means: Shift malfunction
Check the O2 sensor after the catalytic converter.
Your OBD II code reader won't work on that vehicle.
This is not a "Generic" OBDII code. That means that it means diferent things on diferent car makes.
Evaporative emission system purge control valve circuit
trouble code P0420 means: Catalyst Efficiency Low - A Bank
It is the oxygen sensor, if you need to find out what a code means go to obdII codes.com
Trouble code P0445 means:Evaporative emission control systempurge control valve circuit shorted
This code is defined as: Output Speed Sensor Circuit
1723 indicates a/t control relay open or short
Mass or Volume Air Flow Circuit Range/Performance Problem