My book says it's PCM Failure EEPROM Write Denied - Unsuccessful attempt to write to an EEPROM location by to PCM. EEPROM = Electrical Erasable Programmable Read Only Mamory. PCM = Powertrain Control Module. Hope this helps.
Trouble code P0301 means:Cylinder 1 misfire detected
EVAP Emission Control System Leak (Large)
Trouble code P0321 means:Ignition/distributor engine speed input circuit range/performance
O2 sensor Heater Bank 1 Sensor 1
Evap purge solenoid circuit open.
It would be very rare for a P1684 code to turn the light on.
my van will crank, but won't start, had spark plugs change
Cylinder number two misfire.
The P1684 code simply means that the battery has been disconnected within the last 50 starts.
catalytic converter failure.
CHAn9E code
Cylinder number four misfire.