Here's the technical description of the p0340-344 diagnostic trouble codes: P0340 Camshaft Position Sensor Circuit Malfunction P0341 Camshaft Position Sensor Circuit Performance P0342 Camshaft Position Sensor Circuit Low Input P0343 Camshaft Position Sensor Circuit High Input P0344 Camshaft Position Sensor Circuit Intermittent Obviously, the camshaft position sensor (CPS) is the probable source of the problem. See "Related Questions" below for more about the CPS
P0340 Camshaft position sensor circuit P0340 (M) No Cam Signal At PCM No fuel sync.
Test/replace the cam sensor.
Trouble code P0340 means:Camshaft position sensor circuit malfunction
Test/replace the cam sensor.
P0340-CAMSHAFT POSITION SENSOR CIRCUIT, The cam sensor is the pick up plate in the distributor.
Trouble code P0340 means: Camshaft Position Sensor A Circuit (Bank 1 or single sensor)
Replace the cam sensor
You have a circuit problem on the camshaft position 1 sensor.
Nice answer. For any vehicle, try looking up your codes here: http://www.obd-codes.com/trouble_codes/
P0340 says there's a problem with the camshaft position sensor, and P0344 elaborates saying that the signal from it is intermittent (ie, sometimes ok but sometimes not). This can be caused by bad wiring between the computer and the sensor, a bad sensor, a bad flywheel which the sensor reads notches from, or the computer module itself may be going bad. In my research on the P0340 code which my car is getting, web pages say that some engines can in fact run without the sensor, but since it's used to help time the fuel injection and ignition, it will reduce your gas mileage (town mileage affected more than highway). If you notice the engine losing power or stalling out, it might be worth trying to disconnect the sensor and see if it improves driveability. I wouldn't recommend running it like that forever, but if fixing it right away isn't an option, it may be worth considering.
P0455 and P0452 have to do with fuel vapor leaks, will not cause a starting problem. P0340 is a cam sensor code. You need to diagnose for a failed cam sensor.