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Discussion Starter #1
OK, first .... I apologize for this moving around. I was thinking "Interior" or "Electronics" ..... then tonight as I was prepping to post regarding my final "fix" .... I noticed the "General Tech" section and upon further review, I think it belongs here so here is where I brought it. :cool:

ME (aka: CrystalPistol) on 10-02-14 @ 2241hrs said:
Well, for my day off I persuaded "Wife Unit" to take the '95 to work so I could clean and wax her Subaru. Then a buddy showed up on his recently purchased Gold Wing GL1500 and we went over it good, fixed a few items, drank coffee, and talked shop .... etc.

Then "Wife Unit" came home after 5 pm and asked about a flashing "airbag" light. :facepalm:

Never done that before? :zdunno:

Sure enough, 5 flashes ... pause .... 1 flash ..... long pause ..... repeat. Airbag flashing code 51. :(

I looked it up, I realize that there was a short and when the short went away, the code tells me that a thermal fuse is blown. I even found a thread about replacing just that fuse and have just ordered a few fuses to affect a fix for the Airbag Diagnostic Monitor.

But first, before I waste a fuse ... I need to search for the source of the short.

Any ideas y'all? I tried "search" to no avail.

Thanks ..... :zbeer:
ME (aka: CrystalPistol) on 10-10-14 @ 2314hrs said:
I'm sure there's probably a section in the EVTM which breaks out the air bag system. My info on code 51 says "51 Diagnostic Monitor Internal Thermal Fuse - Open Due to Intermittent Short to Ground". I don't know which circuit this short to ground would be - diagnostic system power module, crash sensor, air bags, etc...

If you don't have the EVTM I can probably snap a pic of the page in mine; I don't think the airbag system changed between 95 and 97.
Hey, Thanks .... but yeah, I have the factory "big" book for both the '92 and the '95. Since writing my first post here in this thread, I have gone over every wire in the circuits described and so far .... no signs of shorts.

Funny thing happened today though. This morning early a buddy and I took it to the range for qualifying, all was OK except that persistant flashing code 51. I know, it'll stay until corrected. So afterwards, we came back, total about 80 miles. It was the first time I had driven it since that day the "Wife Unit" used it and that code started.

Well, since it was drizzling rain by then, when I got home I told the "Wife Unit" that we'ld take it to Roanoke this afternoon. When we got in to go, I hit "start" and heard a click and then nothing. All dead. I popped hood and checked cables on near new group 65 battery, negative was loose. I tightened it up and tried, car started and clock was saying 12:00.

So we start towards Roanoke and I'm thinking and start talking and then it hits me, that day she had this Code 51 start I also later found the clock was way off and so I asked her and she said it did show shortly after 12:00 when she looked on the way home even though it was near 5:00 PM but that day .... the car started, just also started that flashing light.

Well, I'm a few miles from home and decide to go back and swap over to another car and not risk another "no start" today. While swapping over a few things, I took a closer look under the hood, and it was then that I saw upon close looking, the negative battery post clamp that's stamped steel had a crack which was why it had loosened up .... and me tightening it was temporary as the crack would only spread.

So, I've been doing some searching on "air bag code 51" and am thinking the loose battery terminal, the clock resetting, and the code 51 aren't so "unrelated". I am thinking that new battery terminal clamps will take care of what the diagnostic sensor saw as a short when she started the car a few days ago and no doubt the loose connection state caused a short and intermitten voltage drop as she started the car and the thermal fuse was blown. This was a short, quick voltage drop after the starter was engaged, likely though while the key was still in start position, and not noticed by "Wife Unit" because car started fast.
I have since received a package of 5 new thermal fuses (NTE8167C (more hits using NTE8167 ... no "C") .... cost me under $10 total for parts, S&H was another $11 though ... but good deal in view of alternatives) to affect repairs to the "unserviceable" Air Bag Diagnostic Module. Gonna try one tomorrow. I have the tools, solder, low temp soldering gun, heat sinks, etc.

Here (that is a link) is where I got the info and it seems pretty straight forward.

As always, I remain open to suggestions, comments, or tales of experiences?

:)
 

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Discussion Starter #2 (Edited)
OK, now the thread is complete and "here" in "General Tech".

I received the 5 new thermal fuses (I ordered NTE8167C but all 5 plastic envelopes have the part number as NTE8167 on them) Saturday, and after a 300 mile drive yesterday looking at "leaves" ..... today I was ready to fix that light. I did go to Radio Shack and get a 45 watt de-soldering type gun, has the suction bulb attached. I am 60 years old, have 5 soldering guns, three are Wellers, have all sorts of electronics type solder, various sizes .... but I never owned a de-soldering tool. A long overdue addition I think.

So first I disconnected the negative battery cable, and let car sit awhile. I also emptied the glove box and popped the "limiter" thing loose on the far right side and eased the box down after pushing in the left side. Located the Air Bag Diagnostic Module up inside on far right, a blue box with two harnesses plugged in bottom.

Un-plugged the harness, removed two nuts and slipped module out and into house. Box was easy to open with small screw drivers, and located and removed the black and white cover from the thermal fuse. There is a resistor there under it that must be in contact with the thermal fuse. I marked the two terminals on back side and then de-soldered the old fuse, that suction de-soldering tool worked great! The new fuse is a hair bigger, slightly larger leads, but they fit the holes. Note the ends of original and orient new same way. Carefully bend leads to fit holes, slide in until against resistor and aply heat sink and the solder on back (I used a small 30 watt gun).

Repeat for other lead.

When done, the fuse and resistor were touching as they should, I then added a small zip tie around the two. The original cover will not fit over the new fuse .... and I may come up with a substitute?

Put the Air Bag Diagnostic Module back in place in the car, connected harness, reattached battery negative post .... great so far.

Open driver's door, and from far side of steering column reached under to insert key and start .... "just in case". Maybe no way for it to deploy, but I wasn't aiming to find out "a hard way".

Car started, lights on to let me know they work, then light went out like supposed to and stayed off. Repeated it all again, and then let car idle a few minutes while I put glove box contents back and shut.

I call it "fixed". ;)

So it appears that a bad battery terminal that is cracked and thus which does not make a firm connection can, on startup, both cause a clock to loose setting when that poor connection arcs and fool the Air Bag Diagnostic Module to see it as a short and blow the thermal fuse .... and then see it as an intermittent short that's no longer present and flash Code 51.

Also, if you attempt this "fix", it is "your gamble" ..... as sensitive electronics are involved.
 

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Discussion Starter #3
Well, today I needed to go to town for a haircut and was getting in the '92 when I thought .... I had not yet driven the '95 since this fix. Don't know why, wasn't skeered or anything, just hadn't. So I moved the '92 out of the way and took the '95 .... 14 plus miles each way and several stops once in town ..... and the "Air Bag" light comes on only at start up to let me know it works, then after a few secs goes out and stays out.

Yep, she's fixed.



:)
 

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It's November 30th, and since last posting I have now put a few hundred miles on the '95 and the light is staying off .... so unless something else happens (I'll update if so) ....
.... this is FIXED for sure.
 

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Original owner 94 TBird 4.6 V8, 141K miles.

After replacing the brake booster and MC (had to disconnect one of the wiper motors) I received a code 51 on the airbag warning light. There was no other code flashed indicating a short in some location. (Perhaps it came on but I did not notice/see it) I went looking for the short especially around the recent work but could not round up the usual suspects. I ordered new thermal fuses (5 came for about $16) and went to work. Disconnected the battery, unhooked the glove box, removed the air bag diagnostic module and inspected things to see if something else (water intrusion) might have caused the problem. I noticed a yellowish fluid in both wire bundle connections and receivers. I suspected the capacitors may have leaked. Upon opening the box however, revealed a very clean and pristine board. I cleaned the connectors with electronic cleaner and a towel and went to work replacing the thermal fuse. It was a snap really, and as noted by others the new fuses are larger and thus the plastic housing will not fit. I wonder if that helps protect from fires if or when the fuse heats up to open. The old fuse had visible heat markings. I tested the heat resistance of the housing with the tip of the solder iron and it melted readily. Who knows? I used a small zip tie to bundle the fuse and resistor and then soldered it in place. Reversed my steps and everything tested okay.

Will give an update if a short reoccurs to open the thermal fuse again.
 

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Discussion Starter #6 (Edited)
Original owner 94 TBird 4.6 V8, 141K miles.

After replacing the brake booster and MC (had to disconnect one of the wiper motors) I received a code 51 on the airbag warning light. There was no other code flashed indicating a short in some location. ... etc ...

Will give an update if a short reoccurs to open the thermal fuse again.
WOW ..... GOOD DEAL! I hope some of what I posted helped in some way. :smile2:

Mine has been perfectly fine ever since, over a year now ..... but today I picked up a Code 41 so the diagnostic module is still working ..... I figure a wire or Rt Frt sensor issue.

Edit 12-10-15:

Here is a link to the thread on my journey fixing that Code 41 (was not a wire or sensor issue, it was another defect part within the OEM module which I have been unable to locate the fix for) ...... which lead me to replacing the Diagnostic Module with another .... that also had a Code 51 issue .... which is also now fixed. :wink2:
http://forums.tccoa.com/6-general-tech/168450-air-bag-code-41-flashing-95-bird.html#post1798722

Also .... in my testing to detect blown thermal fuses, I also have been testing the leads across the resistor that is adjacent to and which must be in contact with the thermal fuse ..... to make sure that resistor is still capable of heating up. So far, in my tests .... those seem to survive.



:smile2:


.
 

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Well I picked up another code on the module. I noticed the warning light flashing as I was driving away and tried to count the flashes to see what the core problem was but I was too late and got the 51.

I am going to replace the fuse once again. I am going to be more alert when I start the car to keep an eye on the light to see if it fails and what code the problem is.

Installed the new fuse (getting pretty good at it) and the car checks out okay. I wonder if the short was related to the wet weather. We shall see in the dry heat of the summer.
 

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Just updating, Thousands of miles and years later, I've had no further issues with this.
 
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