HiCustomer welcome to Just Answer!.
Let's check codes first, Jim. Roll the key from off to on three times and watch the odometer window to see what spills out. Write 'em down, shoot 'em back.
What happened to your Neon, by the way? Was it a no-start one morning or did it die while driving?
Talk in a bit,
I believe it does, Jim!
I think your core problem is the loss of crankshaft position sensor signal. The other codes are being thrown in as decoys...
P0320 indicates a problem with the crank sensor signal circuit or loss of signal.
Without a consistent crank signal, the autoshutdown and fuel pump relays sometimes will code as they're caught with their pants down as an occasional stray signal passes their way. P1388 (ASD RELAY CONTROL CIRCUIT) and P1282 (FUEL PUMP RELAY CONTROL CIRCUIT) are how they read. P1684 indicates a recent battery disconnect, dead battery, or PCM memory erasure. I'd expect it to be just very low system voltage, another side effect of lost crank signal and considerable starter time.
The crank sensor is located on the back side of the lower engine block in this year, just above the oil filter adapter. It's the three-wire connector with grey/ black, orange and black/ light blue wires.
Chances are very good that the sensor simply failed. But there's also a good chance the wiring to the sensor is damaged... by falling onto the right side driveshaft or by heat damage within the loom.
I'd suggest inspecting the loom first to see if it's obviously tangled with the half-shaft. If not, remove the connector and break out the digital volt/ ohmmeter.
With the key on, set the meter to 20vDC and test the orange wire for voltage in the 8v to 9v range. Anything in that range is OK... this is the power source to the sensor.
The grey/ black wire is the signal circuit and should have something very close to 5.0v when disconnected.
The black/ light blue wire is the sensor ground and should have just about 0.0v on the circuit. Switch the meter to 200 ohms and test to see that continuity to ground is 25 ohms or less to battery negative or a good body ground.
If those three checks come out OK, you simply need a crank sensor. It's held in place by a single 10mm hex head bolt and it pulls right out of the block. Lube the O-ring, reinsert and bolt down... no adjustments necessary (or possible).
If you have any problems or questions, just write back, Jim. Be glad to help!
That's a question I can't answer, Jim. The factory code-read feature you used will display any powertrain-related code stored in PCM memory, but it won't show pending (1-trip) codes. By rights, a scan tool should have access to even more information if it's available.
Regardless, you should be in good shape now. Let me know if you run into any problems.