Cadillac introduced the world to the PCV valve (Positive Crankcase Ventilation), which greatly reduces engine emissions. The company released the designs for public use. All vehicles use similar setups to the original design. The GMC Yukon Denali followed suit, and set up the vehicle's emission-control system with the standard style of PCV valve. You should inspect and replace the PCV valve every 30,000 miles. The process takes just a few minutes to unplug the current one and install the new valve.
Raise and prop up the hood to the vehicle once the engine has had time to cool.
Disconnect the vacuum tube connecting to the PCV valve on the driver's-side valve cover near the back of the engine. The vacuum tube is a hard plastic tubing connecting between the third and fourth valves.
Pull the existing PCV valve out carefully. It will just pop out, but be cautious so as not to damage it. Replacing the device requires just pushing the new one into place, and reattaching the vacuum tube.
