There is a TSB on this issue for a failed instrument cluster by ford manufacturer .
I send it to you for your review , there will be several symptoms involved in the failure and the symptoms you are having are listed
The instrument cluster will need to be rebuild or replaced
FORD: 2005-2006 Five Hundred, Freestyle MERCURY: 2005-2006 Montego This article supersedes TSB 06-6-2 to update the Service Procedure. ISSUE Some 2005-2006 Freestyle/Five Hundred/Montego vehicles built before 02/17/2006 may exhibit intermittent instrument cluster concerns with one of the following symptoms: Very temporary intermittant condition at which time the Instrument Cluster pointers will intermittently "home" randomly after the ignition switch is in the run position. This is when all pointers travel to the low end of gauge travel, jitter for two to four seconds, and then recover. This condition may be more likely to occur as the vehicle drives over rough road surfaces. During hard fault or prolonged intermittant condition, most functionality of the cluster will cease operation as soon as the issue is present, including all gages becoming inoperative. While the fault exists, multiple warning lights will be illuminated, Cluster High Speed Controller Area Network (CAN) or Medium Speed CAN network communication with other module(s) will be inoperative, and reverse lights will stay on. If the fault discontinues, the tachometer and speedometer gauges will sweep and then reset. Look for U1900 diagnostic trouble code (DTC) in other electronic modules, as well as P0462/P2067 in the powertrain control module (PCM). These symptoms could be the result of a defective solder joint on the printed circuit board in the instrument cluster.
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