Airbag Code 51 was one of the reasons I was getting ready to dump my 96 E350. I did some research on it, and found several Youtube videos on it. One suggested that the cause could be a problem with the battery cables. That made sense to me, as we had just had a problem with them. In fact, I have been trying to determine the correct lengths so I can have some new, upgraded ones made.

Anyway, the result of the problem with the battery cables is that the airbag control module (which is made of Unobtanioum) has decided that there is a fault in the system, so it burns out a thermal fuse so that the airbag cannot be fired. This is a safety measure to ensure that an airbag won't deploy when it shouldn't, like, say, when you are bombing down the Interstate at 70 mph!

Anyway, to make a much longer story short, the cure is to replace the thermal fuse. Disconnect the battery, wait about 20 minutes to allow the capacitors to drain down, and remove the air bag module. (Blue box under the driver's side dashboard on my 96 E350. Two 5/16" [8mm] bolts.) Remove the cover, remove the old fuse, and solder in a new one. Do NOT remove the resistor and replace it with a second fuse!!!! I saw one Youtube video where that was done. Not good!

Where to get the fuse? Amazon, of course. OR wherever. It's just a 172C thermal fuse. I could not find an exact match, but I did find 170 C fuses. I paid about 10 bucks for a pack of 10.

After the repair, I replaced the module, connected the battery, and no more flashing airbag light!

Just posting this for someone who may have the same problem. With OEM modules unavailable, and rebuilt modules running $300 or so, with no warranty, I think it makes sense to try this for those who can solder small components.

 

This is great info--we should lobby to have it included in our Tech Folder here.

Calling all moderators!

 

1995 E350 - Any reason why I couldn't simply solder a new 172C Thermal Fuse to the points in the red circles? This the back of the little white/black box with the fuse and resistor. I get no continuity across the two pins so I believe the internal fuse is blown. This seems simpler than going through all the other steps to replace the fuse "internally".

THX

 

Bad plan.

The fuse needs to live next to the resistor that is in the same housing. This is so that, in the event of a fault, the controller can send current to the fuse, heating it up, and blowing the fuse. This is a safety mechanism and should not be bypassed.

 

Hey man, thanks for the response. I already cheaped out and soldered the fuse to the back of the PCB. per my plan. Not saying I won't go back and correct it, but so far it changed my error code from a 51 to a 41, which indicates that now there's a prob with the right front crash sensor and I'm trying to track that down for now. For the life of me I can't find an accurate description of where the sensor is located. I also can't find a valid link to get a copy of the workshop manual for a 95 E350. I found one link saying the sensor is on the radiator support but I took the grill out and looked all over, inside and out, and I don't see one. Somewhere else I saw it's on the framerail, but I haven't gotten under the van to check. Any clues?

So my next question is about the fuse itself. You say it needs to be next to the resistor so that the controller can send current to the fuse, heating it up and blowing the fuse. Do you meant to say "so that the controller can send current to the resistor, heating it up and blowing the fuse"? My confusion with that statement is that this fuse is rated at 172°C, which is 341°F, and since most plastic melts at about 300°F, wouldn't the plastic housing also melt if the fuse was relying on the resistor to generate that much heat? I'm not saying you're wrong, just that I'm thinking maybe the fuse gets that hot internally when there's a fault that triggers it, and the resistor is performing the function of allowing that much current to pass which then blows the fuse, and the actual external proximity isn't a factor.

Either way, I won't be driving the van without sorting out the correct controller config, but I would appreciate any insight you could offer on either of my issues.

Thanks again.

 

Take a look at how the resistor is installed with the fuse. There is a copper band holding them together. This is to transfer heat.

 

I saw that in the video and have to assume that it's there for a reason. The fact that the resistor is supposed to get so hot that it will melt its surroundings is what confuses me. A fuseable link does not require external heat, why does this one?

Edit, OK, I'm sold. They need to touch.

 

Glad it clicked for you. For others who may be following, this fuse is not a normal fuse the blows when too much current is passed. It requires an external heat source (the resistor) to melt it. This is basically a fail-safe OFF switch for the airbag, and it's not intended to be a user-replaceable item.

In other words, this repair has not been tested to ensure that it operates according to the original design, so do this at your own risk!

 

Does anyone know what size the resistor is? I can find multiple boards that indicate it's 15 ohm, but no guidance on wattage. I pulled my airbag control module yesterday and the resistor was fried, alongside the fuse, to the point I can't see any text to decipher what I need. I've seen it's maybe .25 watt and found this resistor: https://www.mouser.com/ProductDetail...iABEgJ5KfD_BwE. I'm not sure how close this is to real thing though so looking for any help I can get!

The short that caused the problem has been resolved. Thank you for any help!!! I'm working on a 1994 F-150.

 

"...the airbag control module (which is made of Unobtanioum)..."

Unobtanioum. Thank God I wasn't drinking coffee when I read it or I would be cleaning a keyboard and screen right now.

 

There is another thread around here that says it's a 15 ohm fuse, but I can't find where that value came from.

 

I've found a few of the boards with 15 ohm, but they don't indicate resistor wattage. Have you seen that info?

 

Late to the thread but, did you ever find a solution? Mine looks exactly the same in my 94f150. What was your solution? I can find the fuse and resistor but like yours my housing is fried. Did you find a cause? What fuse and resistor did you come up with? Thanks for the help.

 

Nice video - great idea.

 

I never could find the watt info, so I ended up going to the junk yard. It took me 4-5 trucks to find a board that wasn't shorted, but I finally did pull one. Plugged it in to my truck at home and sure enough it solved the problem -- airbag code went away! I forget what I paid at the u-pull-it lot ... maybe $10. I would encourage you to try the same if there's one nearby you!

As far as a cause, no clue. I bought the truck and it already had the obnoxious beeping from the airbag control module. Guy I bought it from said he went to the dealer and they told him they could cut the wire. Surprised he drove it like that for a long time when it was a pretty simple fix, I'm just happy I don't have to listen to the 5 beeps 5 times anymore!