I have a 2000 Plymouth neon and have been having some issues. When you put the key in and then it to the ON position the lights, radio, and everything comes on inside the car. But the fuel pump is not turning on. And when you go to crank it over nothing happens. No clicks, nothing. We took it to a dealer to reset the security system and got new keys programmed but still nothing. Changed the ignition lock cylinder and ignition switch and nothing happened. I'm stumped.

Hi Susan , when you turn the key to the start position does the starter engage an spin the engine ? If yes , pull a spark plug wire an check for spark , do you know how to do that ? You can buy a spark tester at the auto parts store or stick a screw in the spark plug boot a hold it near ground .( metal on the engine ) Have someone crank the engine . Does it have spark ? If not could be the coil or crankshaft position sensor . Watch this video !

No Start Diagnostic Basics EricTheCarGuy

There is no light to flash for any fuses. Is it the check engine light flashing you are refering to? The radio not working may be a fuse.

According to my source, code 1899 is a problem with the governor pressure sensor. But 4 digit codes are model specific, so you may be right about the selector switch.
If the switch tests out to be faulty, it would need to be replaced and the code erased.

try starting it in neutral

If the headlights and dashboard lights are working but the vehicle still does not start, the ignition switch is most likely the problem. or a bad wire from switch. If your battery checks out, but the starter is still silent, it may be a faulty ignition switch. Turn the key to the on position (not all the way to start). If the red warning lights on your dash don't light up (and your battery connections are clean), the ignition switch is bad. If they do light up, turn the key to the start position. The dash warning lights should turn off at this key position (most cars). If you're not sure, turn on the headlights. When you try to start the car, the lights should either dim (a lot) or turn off completely. If they do, your ignition switch should be ok. If not, the switch will need replacement. check the wires to starter and see if you have power when car is switched on, do this first! good-day! if it cranks but does not start. check to see if spark and fuel, and check all fuses also.

The fuse must be in the main fuse box. The position and function of the fuses is normally marked on the inside of the fuse box cover and also in the owner's handbook. If you don't come right with these, work your way through the fuses looking for a blown one.

The issue will most likely NOT be dash wiring. Something is still tripped. Most likely is there is a switch that trips when one 1/2 of the brakes fail, like the rear wheel cylinder. Try bleeding brakes, again, including OTHER brakes than the ones that you repaired, allowing this switch to move in the other direction. Watch for the light to go out during this process.

P1685 Skim Invalid Key.

The Sentry Key Immobilizer Module contains a Radio Frequency (RF) transceiver and a microprocessor. The SKIM transmits RF signals to, and receives RF signals from the Sentry Key transponder through a tuned antenna ring integral to the SKIM housing. When the ignition switch is turned to the On position, the SKIM transmits an RF signal to the transponder in the ignition key. The SKIM then waits for an RF signal response from the transponder. If the response received identifies the key as valid, the SKIM sends a valid key message to the PCM over the PCI data bus. If the response received identifies the key as invalid, or if no response is received from the key transponder, the SKIM sends an invalid key message to the PCM. The PCM will enable or disable engine operation based upon the status of the SKIM messages.

you can look it up here:
http://www.engine-light-help.com/check-engine-light-domestic.html

linkage is disconnected. most pannels pop off easy to allow acess. then pull the cover away from the position close to key point and see if linkage is loose.

I have the same issue with my 1997 neon. I found that if I wiggle the key in the ignition it corrects itself.