My 2004 neon won't crank over to start unless i disconect the battery and reconnect it. Why?

you need to have a scan tool to read computer. when cranking vehicle do any icons light up? It seems that you have a immobilizer problem which is associated with the key possibly. Try another key. If that is not successful. You will have to have car professionally scanned to proceed with diagnosis try disconnecting the battery terminals positive and negative and touch them together for 30 seconds. Next reconnect cables to battery Then try to start car. The p0499 code should not keep car from starting, unless it is an indicator that the computer has issues . you need to have a high level scanner hooked up to car to read computer sub systems.

Has it been running since you got the new battery? If it cranks good but won't start, have a helper crank it while you visually check for spark at the spark plugs. If spark everywhere, use a gage and check proper fuel pressure. Also, check for fuel injector pulse. If more than one issue, check cam and crank sensor. Check theft/security where applicable.
Don't replace anything unless testing points you in that direction.

don't know if you can but you can try resetting everything. you disconnect your battery for 10 mins (positive post on battery) then reconnect it then start your car.

Sound like seliniod on starter may be bad....

Go under the dash and bypass the clutch pedal safety switch and see if it starts.

clean your battery terminals or replace the cables. your losing your connection somewhere.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/michael_00678fd4800d19c5

Hello You will have to reset your fuel pump switch located passenger side right foot kick panel when you press it it should stay down if this does not work your probably looking at a fuel pump not working.

Yes. Unfortunately, it sounds like it is your fuel pump, and if it is, I believe it's located in the gas tank. Would be extremely hard to replace it yourself unless you have the proper tools, jacks, a lift for the car, etc.... If you decide to do so, write back and I'll provide step-by-step instruction.

look everyone !!! i am not the only one who has this problem , but I found the answer on my own.... iI hope this can help others . If you have to replace a neon engine you must do these thing if you want it to start.
<br>
Lower vehicle and perform camshaft and
crankshaft timing relearn procedure as follows:
² Connect the DRB scan tool to the data link
(diagnostic) connector. This connector is located in
the passenger compartment; at the lower edge of
instrument panel; near the steering column.
² Turn the ignition switch on and access the “miscellaneous”
screen.
² Select “re-learn cam/crank” option and follow
directions on DRB screen

Most people don't have access to this scanner <but it must be done> I used a snap-on cost 3000 but have the reset feature

Thanks you all for your help.

i shoul not afect any thing unless you replace the batterie with the car runing, and some radios have antitheft code if batterie die or disconect the radio will ask you to type a code in order to work again but most of times it display the worl code on the digital screen