I just bought the car 2 weeks ago. Always had a semi-rough idle while stopped in gear... You can literally see the hood vibrating. The engine did stumble 1 time about 4 days ago while I was sitting at a red light. It was a pretty hard thump from the engine like it was about to stall out, but it caught itself when I let off the brake. The check engine light came on today, code: P0340 and P1684. I was told P1684 is nothing to worry about, but I've seen a few people say that P0340 lead to the engine not starting because of timing belt failure. The guy I bought the car from told he just put one on last year (no proof though). It's a 2000 Dodge Neon. 161,000 miles. Automatic. ANY INFORMATION would be cool. Thanks.

 

i would def change it.not to put down the guy who did it but it sounds like he didnt put it on right.a timing belt is very critical because you can mess your stuff all up.my friend had a eclipse gt v6 and his timing belt slipped and he blew 3 cylinders.

 

it could be could be the cam sensor but if it was me I would do the timing belt anyway just for some peace of mind

 

P1684...I don't even understand why they made a code for that.

P0340 is the camshaft position sensor circuit malfunction (from http://www.obd-codes.com/p0340). It can be more than the sensor.

Symptoms can include:

• Hard starting or no start
• Rough running / misfiring
• Loss of engine power

A code P0340 could mean one or more of the following has happened:

• a wire or connector in the circuit could be grounded/shorted/broken
• the camshaft position sensor may have failed
• the PCM may have failed
• there exists an open circuit
• the crankshaft position sensor may have failed

If you get a code for the CPS circuit, replacing the timing belt is, simply put, dumb, if you are doing that to try and fix the CPS circuit code. The timing belt has nothing to do with anything else other than the engine timing. Now, replacing it because it needs to be done or you unsure if it has been done and it is past due...completely different story. You'd be smart for erring on the cautious side for that, as a broken belt will destroy the valves in the head.