camshaft sensor and or cam phaser diagnosis

camshaft sensor and or cam phaser diagnosis Check engine light is on. The codes says camshaft sensor. so i replaced both sensors still the same. i have read that it is probably the cam phaser. when i drive at around 35 to 40 mph it feels like i am driving over rumble strips in the road. but when i get to about 45 to 50 mph it stops.