Codes

a google seach comes up with this: http://www.fixya.com/tags/p0303_p0304/cars/dodge/neon personally think that high maintenance items should be suspected...coils do not go bad by themeselves...power to the coil may get rusted tho...personally have changed the oxygen sensor...then the check engine light will go off~...those are some hefty codes tho...system GROUND...assure the battery can get to the brain...the wire that connects to the battery should be looked at...sounds like it just could be a wirebrush at the battery fix...no money needed...tho an oxygen sensor if you've got 30-60,000 miles might be considered an maintenance item~ so clean the battery connections...especially the ground to the ECU~

2003 in the "rust belt" could probably be the concern!~

Your po300 code indicates random miss fire, po302,303 are just the miss fire in cylinder #2 & #3, The po300 covers these... Possible causes po300, 302, 303.....> - Faulty spark plug (s) - Faulty ignition coil (s) - Clogged or faulty fuel injector (s) - Intake air leak - Fuel injectors harness is open or shorted - Fuel Injectors circuit poor electrical connection - Ignition coils harness is open or shorted - Ignition coils circuit poor electrical connection - Insufficient cylinders compression - Incorrect fuel pressure.........>>po344 Possible causes...> - Faulty Camshaft Position Sensor - Camshaft Position Sensor harness is open or shorted - Camshaft Position Sensor circuit poor electrical connection - Faulty starter motor - Starting system circuit - Dead (Weak) battery Tech notes Sometimes and in some models, low battery voltage or a weak starter can can trigger a Camshaft Position Sensor code....>>P0456 DODGE - EVAP System Small Leak Possible causes po456...> - Missing or loose fuel cap - Incorrect fuel filler cap used - Fuel filler cap remains open or fails to close - Foreign matter caught in fuel filler cap - Evaporative Emission (EVAP) canister or fuel tank leaks - Evaporative Emission (EVAP) system hose leaking - Fuel tank leaking

all of those faults all at once? think there is a common denominator...and that is of an electrical nature...reconsider cleaning all grounds...perhaps with brake cleaner to assure good connections...would be SAD if you spend money solving all those faults when this might be a simple power problem...that's my two cents worth...take it or leave it!~

The po300 codes are all basically the same causes. The po344, and po456 are separate issues. Camshaft sensor problems, and emissions issue.