Code 51 Diagnostic Monitor Internal Thermal Fuse Open
Diagnostic monitor measures voltages at diagnostic monitor terminals. When certain air bag deployment wires are shorted to ground, system may become susceptible to unwanted deployment of air bag. Diagnostic monitor senses a short to ground and helps prevent unwanted air bag deployment by blowing diagnostic monitor thermal fuse. Blowing this fuse removes all power (battery and back-up power) from air bag deployment circuits. If short to ground exists, diagnostic monitor will flash Code 13. If short to ground is intermittent and temporarily corrects itself, Code 51 will flash. If short to ground returns, Code 13 will flash instead of Code 51. If Code 51 is flashing and short to ground has not been repaired, an intermittent short to ground exists in air bag circuit. DO NOT replace diagnostic monitor unless short to ground has been located and repaired.
Code 51 will set if there is a short to ground in circuit No. 623, 614, 615, 617, or 619. 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.
Check For Short To Ground
Inspect circuits No. 623, 614, 615, 617 and 619 for short to ground. Inspect wiring harness areas where wires pass through or are located next to metal components. Repair as necessary. After repair is completed, check AIR BAG warning light for codes. If Code 51 exists, deactivate air bag system.
Replace diagnostic monitor.
NOTE: Code 51 is displayed whenever diagnostic monitor thermal fuse is open and no other higher priority faults exist. Code 51 is normally seen after service of a Code 13 condition. If a Code 51 exists and a Code 13 condition has not been serviced, an intermittent short to ground exists in air bag deployment wiring. Intermittent short to ground must be located and serviced before servicing a Code 51 condition.
January, 2, 2010 AT 2:19 PM
This happens on my van due to the fact that the previous owner took out the airbag (afraid of the technology). Now that it is missing. The light constantly flashes.