same problem here caddy sdi ayq 2003 limp mode . i sent ecu away  but came back still  in limp mode , no faults  on ecu as checked  by snapon vag computer,  just going to sell it now  as  parts  and spears ,,  sad thing is  i realy took great care  of my van , only 57000 miles  and still has  plastic  on carpet from new  ,,,
                 paul
                
 July 2013