how to repair a digital speedometer on grand marquis on 2006 Mercury Grand Marquis

every thing eles is working on my 2005 grand marquis except the digital sppedomer. i replace te whole cluster with a used one and still have the same problem. PLEASE HELP. THANK U

Scan test of BCM should help.
1 more answer
Common Problem with these clusters. They can be expertly repaired here: