Applying the proper lubrication may correct the following problems in
  many cases:
|     •  | Binding door lock cylinders | 
 
|     •  | Sticking door lock cylinders | 
 
|     •  | Keys that are hard to insert | 
 
|     •  | Keys that are hard to remove | 
 
The recommended material for lubricating these components are in order
of preference:
|     •  | Lubricant GM P/N 12345120 (Canadian P/N 726548),
 or the equivalent | 
 
|     •  | Silicone spray GM P/N 1052276 (Canadian P/N 726548),
 or the equivalent | 
 
Penetrating lubricants, such as GM P/N 1052949 and WD-40®,
  are not recommended because they wash out the original lubrication. These
   lubricants will eventually evaporate and leave little or no lubricating
 material.   If you use these materials in order to unfreeze or loosen the
 lock cylinder   components, refer to steps 2 through 4 for the proper
 method of lubrication.
You may repair lock cylinders that freeze due to cold weather by using
  the following procedure:
- Apply heat to the lock cylinder with a heat gun. Be careful not
  to damage the painted surfaces.
 
- Hold the lock cylinder shutter open with a paper clip or similar
  item. Force air into the lock cylinder using compressed air and a blow gun
   attachment.
 
- While holding the lock cylinder shutter open, inject a small amount
  of lubricant refer to the recommendations into the lock cylinder.
 
- Work the key into the lock cylinder several times. Wipe any excess
  lubrication residue from the key.