Code P0018, Camshaft Sensor?

A correlation code shows that the sensors are working. It basically means that the ECU sees a difference in the ratio it expects to see between the cam position and the crank position. So as an example, say it's a chain driven camshaft with a 2 to one ratio. So, the crank turns 360 degrees while the cam turns 180 degrees. However, the chain stretches and now the crank rotates 380 degree, and the cam only turns 174 degrees (1-2 teeth off correct timing). That leads to the code. It also shows that the sensors are working. In your case I suspect that the cam phaser is sticking and will need to be replaced to make the code go away. This could be tested with a scan tool; you would look at the state of the OCV (on or off) and look at the camshaft timing as you toggle the valve on and off. If the timing stays static, then the phaser is stuck, or the valve isn't getting the signal. To test for the signal you could use a test light attached across the terminals for the control solenoid and then toggle the signal on and off. If the light follows the switching it shows the wiring is good. However, that would lead to a stuck phaser. For that you would need to remove the timing cover and physically check the timing. If you find, then that the timing is off, I would suggest doing a phaser and timing chain replacement because of the mileage you have.