Code 12: Battery disconnected with in the last 50 key cycles. Code 55: End of messages. Nothing on those two codes to worry about.
Code 51: Fuel System Lean. Might be a vacuum leak, bad 02 sensor (your van only has the one before the cat), low fuel pressure.

Does this engine have a lot of pinging sound? Or have you replaced or know if the Intake Plenum pan gasket has been replaced? If not that could be the vacuum leak if you do not find another source. Try this TSB to confirm if the gasket is good or bad:
http://dodgeram.info/tsb/2000/09-05-00.htm

 

after knowing this about the codes and engine light....How come I didnt see the engine light on prior to the coil going out? the light never came on before. I believe the 51 code is a o2 sensor...how hard is that to change and is it expensive? This van isnt actually mine van it is a maintenance van that my job owns, I am just trying to save some money and repair it myself, the van has like 270,000 miles on it...well thanks for all the info.

 

you say possible low fuel pressure..could it be a dirty fuel filter??? I havent change the intake gasket and dont know if it has. it is a hazard to run the van with this code active??? I could have loosen something while looking the motor over...that is something i will look into as far as the vacuum system.

thanks

 

The 02 sensor is about 50-60 dollars. Not to hard to change unless you live where there is a lot of salt used on the winter roads.

To find it look under the driver side of the van about where the drivers door latch is and you will see the exhaust pipe, the cat is before the muffler and where the two pipes enter the cat on the side by the transmission is the sensor. At the auto parts store ask them for a O2 sensor socket. It will help with the removal of the sensor itself. Just back it out like a bolt and install the new one. Member Stev has pointed out not to use the Bosch sensors but use either Denso, NGK, or Delphi sensors instead.

 

Possible on dirty fuel filter, how old is the fuel pump module? The fuel filter is built into the module.

Do double check the vacuum lines since the code was not set before the failure of the coil pack.

 

Just to throw my 2 cents in...12 and 55 just mean the start and end of the code reports. Code 51 indicates a lean condition, which could also just be a vacuum leak or a bad O2 sensor.

 

ok, thanks...I actually removed the negative battery terminal to reset the codes...the check engine came back on after 10 minutes like before, but after restarting and driving some more, I haven't seen the check engine light back on, so we might be ok now, but I haven't had the van up to proper highway speeds yet due to the poor road conditions - I live in CO. I have use the van yesterday and the light never came on, so I will keep my eye on it.