Modern vehicles use on-board diagnostics (OBD) to monitor a vehicle's components, and to relay issues via OBD-II codes to a central computer. Different elements within the system produce different codes. Dodge Neons use manufacturer specific codes in addition to generic codes. Code P0340 indicates a short or open in the camshaft position sensor circuit, a damaged camshaft position sensor, an issue with the camshaft, a damaged timing chain, or an issue with the Electronic Control Module (ECM). Troubleshooting the cause is a multiple step process.
Check the resistance in the camshaft position sensor circuit using an ohmmeter. Disconnect the camshaft position sensor (a two-pronged male connection going into a female connection, located beneath the manifold adjacent to the camshaft) and insert the ohmmeter terminals into the female connection. Resistance cold should be between 835 to 1400 ohms. If the engine is warm, it should be between 1,060 and 1,645 ohms. If the resistance is outside of those levels, replace the sensor.
Check for an open or a short in the male connection. Trace the line to where it connects to the vehicle's computer (near the battery). Disconnect the line from the battery and plug one end of the ohmmeter into the sensor side and the other end of the ohmmeter into the computer side. Check for continuity (the resistance should register less than one ohm). If the measurement is higher than one ohm, replace the cable. Also inspect for damage to the harness on both ends. Any damage or corrosion requires replacement.
Visually inspect the timing belt. Remove the access plug from the top portion of the timing belt cover (located on the side of the engine towards the top near the firewall) and visually inspect the timing belt. Verify that you can see the belt and it appears tight. If you do not see the belt, it has broken or slipped.
Replace the access plug. If all aspects of the diagnosis check out, the timing is likely off on the engine. Correcting the timing will repair the issue.
