What does this repair code mean for a 1998 dodge neon 4 cylinder, codes 12 and 55???

See this thread:

http://www.fixya.com/cars/t21943979-2001_dodge_neon_received_code_p1390_mean

have 2001 dodge neon that received the code p1390 what does this mean

Without trouble codes you are fishing in the dark. If the engine has a cylinder that is dead at idle from a fuel injector or ignition problem, it should have a code for a miss on that cylinder. A mechanical problem like a burned valve could cause the problem without setting a code. Have you checked compression on all 4 cylinders ? ?

coil pack may be bad

The codes you listed starting with 3 are for cylinder miss on those cylinders. Code 300 is for a random miss.
Code 462 is for a problem with the fuel level sensor circuit.
Generally speaking, trouble codes for any vehicle built after 1996 are 3 or 4 digit. So is code 43 actually P0043 ?

I'm not sure that is a valid trouble code for your car. The code for Dodge is for a wastegate solenoid which is normally used on turbo engines.
The miss could be ignition, fuel, or something mechanical.

First see what code is in the computer.Cycle the key three times and stop when it in the run position. The check engine light will start blinking. The first code should blink once then pause, then two blinks.This is showing that it is in the diagnostic mode. read all codes the same way, untill it starts with 12 again. Write them down. Then remove the negative cable from your battery post,after one minute, replace neg. cable. The light should be off.If it comes on again, it has set a hard code. You must repair whatever the codes indicate. Get a list of trouble codes online at Google.

CHECK FUEL INJECTOR WIRING TO NUMBER 4 INJECTOR,HOOK A TEST LIGHT TO MAKE SURE IT BLINKS WHILE ENGINE RUNNING.THAT WAY YOU WILL KNOW IF PCM FIRING THE FUEL INJECTOR OR FAULT AT THE INJECTOR WIRING OR YOU HAVE INTAKE LEAK LOW COMPRESSION TO THAT CYLINDER BECAUSE OF BAD BURNED OUT VALVE.COMPRESSION TEST TO THAT CYLINDER CAN ALSO HELP.LOOK FOR LOOSE OR WORN DAMAGE ROCKER ARMS IF YOU HAVE A SOHC SINGLE OVER HEAD CAM ENGINE.

These codes are codes regarding failure. The code P0300 means repeated Engine Misfiring. The code P0303 means Repeated Misfiring of Cylinder Number 3. Kindly contact a technician to get both checked. Their Heads must have been misplaced or broken due to misfiring.
Thank you sir, Have a nice day.

po304 means cylinder 4 misfire detected

po344 means camshaft position circut intermittent

code 71 means #1 cylinder missfire 72 Means #2 cylinder missfire 73 means #3 cylinder missfire and 74 means #4 cylinder Missfire