Hello, My name is Sarah. I have a 2001 Dodge Neon, it has a little over 60,000 Miles on it, Manual transmission, OBD code P1684. My car cranks but won't turn over, I have recently replaced all the spark plugs, the fuel system is good, I have fuel pressure, I also just a few days replaced the TPS because that was a code I had gotten along with the one now, after I changed the TPS, the code for it went away. now I have just 10 min ago did the complete computer reset for the car just to see if maybe it would start then. The only thing I think it could be is that I might not be getting any spark but I have no way to check that. However, if I do have spark....what else would prevent my car from starting??? It's been down over 2 weeks and I'm a single mother and I'm almost at a witts end with this, Please help....thank you for your time.
Here's info on the P1684 code, it seems the most common cause is the battery having been recently disconnected either deliberately or due to a bad connection but it could indicate a more serious problem as well:
https://mechanicbase.com/trouble-code/p1684/
Assuming the engine is in good mechanical condition you need both spark and fuel for it to start. To narrow down the problem you can try spraying some starting fluid into the air intake. If you have spark the engine will fire up briefly, meaning you have a fuel delivery problem. On the other hand if the engine does not fire up you have no spark. (You say there is fuel pressure, but are the injectors firing?)
Chuck Tobias, how do I see of the injectors are firing?
As I said, a quick and easy way to see if you have spark but no fuel is to spray some starting fluid into the engine air intake. If it briefly fires up you know you have spark and the problem is fuel delivery which in your case since you have good fuel pressure would mean injectors not firing.
Beyond that you can use a noid light or fuel injector tester.
https://www.youtube.com/watch?v=5MmR-wXddVw
https://www.youtube.com/watch?v=W3pTeWO3ohc
Chuck Tobias, I got a new fuel pressure regulator and now I've got 70psi for fuel pressure, replaced the cam sensor and still no start. I have to pump the hell out of the gas pedal for it to try to even start
Did you try the starting fluid test to verify spark? How is compression on that engine? What do the spark plugs look like?