Possible Causes
WARNING: This page is about a different car, the 1993 Mercury Sable, 1993 Lincoln Continental, and 1993 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
Code 51 will set if there is a short to ground in circuit No. 614, 615, 616, 617, 619, 623, 624 or 625. A deployed air bag may also cause a Code 51 to set. When air bag deploys, internal wiring of air bag may become shorted to metal housing inside of air bag.