Airbag warning light code. What does it mean?

stang&2Birds said:

Hmm, every try the search function on the forum?

http://www.veryuseful.com/mustang/tech/airBag/airBag92.html

You have a code 51, that's not good in terms of easy debug.
You likely had codes before - something like a code for a bad sensor.
51 Diagnostic monitor internal thermal fuse open

Thankfully, the diagnostic monitors are cheap now. My guess is that you'll go through 1->3 of the monitors to hunt down the problem.

Note: You get two KEY TURN ONS before the internal fuse will blow. So, after the second, disconnect the battery, put your foot on brake pedal for 15 secs (to drain the caps in the EEC, radio, etc), wait 5 mins, connect battery, and you have get two KEY TURN ONS before the internal fuse will blow.

If you didn't get any codes before, it could be because of the "old electronics". Your best "bet" for best electronic life of a new diag monitor would be from a Northern Cold state, and from a car with low mileage (hopefully correlating to engine run time). Commercial-grade capacitors are the "most likely" to fail from age, use, temperature (use Google if you want to know more).



http://www.veryuseful.com/mustang/tech/airBag/airBag92.html
51 Diagnostic monitor internal thermal fuse open

http://www.veryuseful.com/mustang/tech/airBag/airBag92.html#CODE51
Fault Code 51 - Diagnostic Monitor Internal Thermal Fuse - Open Due to Intermittent Short To Ground
Description: NOTE: The microprocessor inside the diagnostic monitor controls the internal thermal fuse. This fuse is not serviceable. The microprocessor will open the thermal fuse whenever a short is detected in the deployment circuits. The thermal fuse does NOT open because of excessive current flowing through it. DO NOT attempt to jumper out the thermal fuse with a circuit breaker or any other type of fuse.

NOTE: DO NOT install a new diagnostic monitor until the short has been located and corrected. If a short to ground has not been located and corrected, then the short to ground is intermittent and IS NOT PRESENT AT THIS TIME. If you install a new diagnostic monitor while there is an intermittent short in the system, the new diagnostic monitor will also open its thermal fuse and require repeated repairs.


Thankfully, the diagnostic monitors are cheap now. My guess is that you'll go through 1-3 of the monitors to hunt down the problem.

Note: You get two KEY TURN ONS before the internal fuse will blow. So, after the second, disconnect the battery, put your foot on brake pedal for 15 secs (to drain the caps in the EEC, radio, etc), wait 5 mins, connect battery, and you have get two KEY TURN ONS before the internal fuse will blow.

If you didn't get any codes before, it could be because of the "old electronics". Your best "bet" for best electronic life of a new diag monitor would be from a Northern Cold state, and from a car with low mileage (hopefully correlating to engine run time). Commercial-grade capacitors are the "most likely" to fail from age, use, temperature (use Google if you want to know more).

The debug of a code 51 gets involved quickly. If a new diag monitor doesn't show the initial/main cause (remember, you get only 1-2 key turn-ons), and the procedure on the web page isn't clear (really requires some electronic and DVM experience), then a dealer may be the best bet. My "100% pull it from my *ss guess" is ~~$500 (+/- $3,000 ).

Good Luck!

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stang&2Birds said:

IMHO, you can get an air-bag monitor for ~$30
http://car-part.com/ (or ebay).

For ebay, use the following search:
air bag mustang (92, 93)


So, it might be worth the try to put another one in, and see if it just works (unlikley), or if it throws out the code(s) for the real problem.

If there are codes, just disconnect the air bag monitor until you fix the problem.
Note, that without the air bag monitor, you will not have any air bags.


If you have it fixed, you want to go to a dealer, and not a local station. The dealer will have access to the diagrams. And, more importantly, mechanics who specialize in electrical/wiring problems.

The Fox air bag system is simple (on purpose). For an electrical specialist mechanic, it would be simple. The cost uncertainty is if a wire is bad or shorted. Hunting those done, and fixing them, can sometimes be very time consuming.


Good Luck!

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