P0335 is the code for the engine RPM sensor and P0340 is the code for the Camshaft sensor. If both of these signals are not received the engine will not start because the ECU does not know the engine turning. So assuming there is nothing mechanical at fault such as a broken cambelt the obvious place to start looking is the crankshaft sensor. The easiest way to test it is by using the scantool you presumabley used to extract the fault codes. Select Live Data and look at Engine Speed. Crank the engine and the speed should be displayed. If it isn't and shows zero that'll be your problem. It's an inductive sensor on these and you check it be measuring its resistance which should typically be between 150 & 1500 ohms. Then check the sensor by measuring its voltage output which should be at least 0.5 volts AC on cranking. Remember to check that using AC volts, not DC volts. If your sensor measures outside of these values it needs to be replaced.....