Check the O2 sensor after the catalytic converter.
The check engine code PO136 means the O2 sensor circuit malfunction
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
This is not a "Generic" OBDII code. That means that it means diferent things on diferent car makes.
Your OBD II code reader won't work on that vehicle.
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
Mass or Volume Air Flow Circuit Range/Performance Problem
1723 indicates a/t control relay open or short