what function does this sensor do...... my truck seems to be running fine.... thanks alot for helping me out.....

We need a little more info.
Year make and model and engine and transmission and mileage to start with.

P0340-Camshaft circuit malfunction-could be an intermittent malfunction?

1997 Chev. Tahoe, 5.7 engine with 130K miles Automatic transmission.

As said the code is for camshaft sensor circuit.
But note it says circuit which could be bad wiring or circuit to.
Proper testing should lead to the problem with it.
Good luck
MT

bought sensor, rotor and cap from dealer..... and light is OFF.... thanks alot for helping me out......BYE

bought sensor, rotor and cap from dealer..... and light is OFF.... thanks alot for helping me out......BYE

I'm glad that worked out for you. Thanks for posting a follow-up also.