15766 - Customer Satisfaction Program. Certain 2015 model year Chevrolet Silverado HD and GMC Sierra HD model vehicles equipped with the Duramax Diesel 6.6L Engine (RPO LML) may exhibit engine harness chafing on the EGR stud. Dealers are to inspect the harness for damage, reroute the harness, and install a clip onto the EGR stud.