Have a 2005 GMC 2500 HD Duramax LLY with approx. 38,000 miles (just out of the 36K std warranty). Occasionally my cruise control will not engage. After driving awhile, it usually engages correctly; or if you stop and restart the engine, it will work. I had the same problem on my 2001 and 2003 Duramaxes. Is there a permanent fix?