On the oil filler tube, the PCV valve is installed, using two tab latches that attach into a cam lock, locked with an O-ring. Before anything, ensure to unhook the rubber hose connecting to the PCV valve. After that, rotate the valve away from you (counter-clockwise) until the locating tabs become loose from the cam lock and pull it out directly, taking care not to push too hard on the tabs. After taking away the O-ring, check its state. To install the PCV valve, set it on the end of the oil filler tube, match the locating tabs with the cam lock, then press the valve up and rotate until the slight click shows it is fixed. Attach both the PCV line and the rubber hose to the valve again when you're done.