RE: Trouble code P0340
The car will start and run without the cam signal, but it will run in "limp-home" mode and batch-fire fuel injection - like crap, in other words.
First step, make sure the sensor is actually plugged in. It's on the driver's side of the head, looks like a square with a raised circle. Also check the wiring from it back to the computer and make sure it isn't shorting out somewhere. Replacing the sensor only takes those 4 bolts and a few rags for oil. Don't know how much the part runs, maybe $30-50 depending on where you shop.
Best of luck!
1995 Plymouth Neon
2006 Mazda5 Sport
I know nothing about cars or engines, at least according to Neon2.0T. Must be true then!