Check the crevices or grooves, for grime build-up that might be the source of the odor. Baking soda paste and vinegar are both useful for removing odors. The crock pot lid is generally dishwasher safe and so a cleanse in the dishwasher should properly clean the lid and remove build-up and odors. However, sometimes the dishwasher can be the source of odor in these things. In which case, check out whether the dishwasher needs cleaning or deodorizing