Well, just installed the new airbag diagnostic module and when we started the car -- we now have a "flashing" airbag light. Five flashes which the book says is a front crash sensor malfunction. There are 3 so it could be any one or maybe something else entirely.

Question: can you reset the airbag light like you can the check engine light? I'm wondering if just changing the module might give you an error. The FSM doesn't say anything about a reset or any other step necessary after changing the module --- any real world experience with this?

As always, THANKS for any help.

ppritchard@cfl.rr.com

 

The airbag system really work pretty well. The front crash sensor is probably the one by the hood latch, the wiring runs all along the passenger side of the engine bay.

I've never had to troubleshoot the airbag system (I actually pulled all my airbag stuff out ) but I'd follow the troubleshooting guide in the shop manual. You may have the sensor disconnected or a bad wire or something.

Dale

 

What about the ability to "Reset". Is there such a function for the airbag light, can't find anything in the FSM about it.

Thanks

 

Figured I would attach files from the service highlights manual in case someone else has a flashing airbag light.



From looking the second atachment you may have a D sensor that has closed continuity. Due to it saying "D-sensor on". I would unplug all three sensors and check for continuity there should be none if it is "good".



John

 

Thanks.

Do I check the continuity "at the sensor" or at a connection point elsewhere?

The diagram on page s-31 shows checking terminals c and D -- but the picture looks like we're somewhere else rather than at the actual sensor?

Thanks

 

^ I do not know what manual you are in. Page s-31 for me is something totally different.


I would try to check continuity right at the plug.I attached two pics from the wiring manual showing where the plugs are. I would think there are more right at the sensor that is not shown.


John

 

Thanks for those.

I was referecing the 93 Workshop Manual. for whatever reason, there are at least two S sections in my Green Manual. The second S is all Air Bag info. Sorry for the confusion.

 

It is unusual for the "S" or "D" sensors to just suddenly cause a problem. If it were my replacement Diagnostic Module, I would pull its cover off and look on the PC card under the electrolytic capacitors for stains. If any are there, there's a good possibility that one or more of those caps have leaked electrolyte onto the board and are causing the flashes. I haven't looked at our 94 FD's diagnostic module, but the manual's System Diagram is an exact match for the 1.6L Miata's System Diagram, and many Miatas have been plagued with bad capacitors in that part.

You might want to check out this Miata Forum thread on this problem. (The good stuff starts at post #8.)

You also should not allow the Diagnostic Module to continue to show a fault, since over time that will blow out the "System Down" fuse, if the problem is in fact in the module. (That fuse is not replaceable.)

 

I had the 10 flashing air bag light a while back. Part of the trouble-shooting included checking the crash sensors. If the sensors checked o.k. the next step was to "replace the Diagnostic Module" which is unobtainable. I tore into mine and found that the capacitors that act as a battery for the DM had gone bad. I replaced them and the DM has worked flawlessly for the passed 2 years or so since repair. Here is a link to my repair if you hit a dead end checking the crash sensors.


https://www.rx7club.com/3rd-generation-specific-1993-2002-16/93-diagnostic-module-rebuild-807185/

 

Read your link for the first time, IMZman, and am very impressed with the detail. I have one question: How do you know that the 1/4w, 10-ohm resistor is actually being used as a fuse? On the Miata, the "System Down" fuse is a much larger unit, wrapped in some sort of foil. And it is terrible practice to design in a resistor, hoping it will act as a fuse. Are you sure that resistor is in fact the infamous "non-replaceable" fuse?

 

As a follow-up, I have attached a picture of the Miata Diagnostic Module's PC card. The large red component with the silver "wrap" in the lower right corner of the picture is the "System Down" fuse. This picture also shows evidence of capacitor leakage.

 

Yep, I am pretty sure that 1/4w 10 ohm resistor is the fuse. It says "fuse1" just to the left of the leg...and it was burned when I removed it. My old man who is a rocket scientist (electrical engineer) confirmed this also. Resistors used to be used all the time as fuses on TV's and other electronics back in the stone age. Also, there was some reason why a 1/4w was used...something about the speed/timing needed to deploy the airbag in an accident vs some other anomaly (unintentional deployment).

I have been known to be totally **** backwards wrong about stuff from time to time...so take the above with a grain of salt. All I can say for sure sure is...the damn thing works since I tweak it ;-)

 

IMZman,

I don't doubt that the 10 ohm 1/4 watt resistor burned up or that replacing it and the caps fixed your problem. But I do think that the "Fuse 1" I.D. in your picture refers to the rectangular green component to its left, rather than to the resistor.

(Don't know for sure, but it sure looks that way to me. Picture copied and attached below.)

 

I'd have to go back and ask the old man...but I don't think that is a fuse. There is another one of those green jobbies at the top middle of the board and there is only one fuse.

 

Old man says it is a "fusable resistor" denoted by grey or light blue color (among other indicators, varies with manufacturer). He says they are common.

 

IMZman,

Ok, thanks for clearing that up!

 

I see the connector on the passenger side of the engine bay for the front crash sensor.
Anyone know "where" you test the left and right front crash sensors? Directions say to unplug all three and check with Ohm meter.

thanks

 

Pictures of fusable resistors below...Scroll down to " Images of Fusable Resistors" and open it. Hundreds of images...if you have patience, you will even see the one on my board!

http://www.google.com/search?q=fusab...&client=safari

 

They are located behind the plastic wheel wells...if memory serves me correctly...remove wheel, remove front half of wheel well fasteners, pull the well back and the orange and blue connectors are visible.

 

If you are talking about the connectors from the front impact sensors into interior it is easiest (in my humble opinion) to remove the fender and undo them.

 

^ That IMHO is one way I would not do it. Only because my car has never had the fenders taken off, and I would not want to crack the paint by the bolts. Is that the only way to do it? I think the last time I had my fender liners off I could see the plugs by the rear of the tire close to the firewall.

OP, I think you may be able to check the continuity at the diagnostic box. Attached are where I believe you can put the probes for that test. hopefully someone else can confirm my markings. One problem that I see with this and all of these tests is that the wiring is still routed by the fenders. Is your car low? Maybe the tire wore through the harness causing the diagnostic box to show a fault?

Also, Because there may be a ground fault in the system, in addition to checking for continuity through the D-sensor, use one probe in the plug and the other one on a good chassis ground.

I see no way this will be easy for you. Hopefully you can fix this with out taking off the fenders.


John

 

Please note I said easiest. =)

Someone else mentioned going through the fender liner which seems like a huge PIA to me. I have my fenders off at the moment and can take a picture for you if it helps you visualize.

 

Correction...I had it *** backwards...remove aft half of wheel well fasteners to get at CS plugs. Wasn't a PITA at all. You can do it at the DM too...but you gotta be limber.

 

I'm going to piggyback on this thread if I may:
My rex just started with 3 flash pattern of the airbag light, which means "open circuit or poor connection of power source circuit".

I'm an idiot and have no clue what to do with this information. Could someone indicate where I should start looking?

Thanks.

 

i