Air Bag Light on Continuously - Kamikaze Approach
 

Two days after successful completion of replacing vacuum hoses with Viton on my wife's '94 FD, the airbag light went on for the first time. A continuous burn, at first for about 1 minute after starting (then fade out), then later, on continuously. Checked the diagnostic module connector terminals (gold, perfect condition), then pulled the module. The printed circuit looks fine. "Fuse 1" measures 5.7 ohms, but the component is marked like an 8.2 ohm resistor, so I don't know what's going on there. No leaky capacitors; all 4 biggies (3300 microfarad, 25V) look good.

I priced a new diagnostic module, P/N FD15-67-7F0A, at the Mazda dealer, at $715!! (And I don't even know if it is really bad.) The original in our car (P/N FD15-67-7F0) is a Naldec product. Some research turned up the fact that it was a subsidiary of Mazda, sold in Sept. 1999 to Visteon Automotive Systems, which is apparently a Tier 1 supplier to Ford. Am trying to find out if there is any technical info (like schematic) available, or possibly a facility that can test the unit to see whether it is bad or OK. No info back yet from Visteon.

In the meantime I have jumpered pin 2A to 2B in the smaller of the two module harness connectors. This grounds the base of the transistor driver for the airbag light, turning it off by simulating the normal "low" output to the transistor at pin 2A. (My wife says she would rather have no airbag function than pay $715 to fix the system.)

Does anyone have experience with the continuously-on airbag fault light who found another cause besides the diagnostic module?

Thanks!

---- Bill

First, you should be able to get a good used module VERY easily and cheaply.

I just checked the airbag codes in the shop manual, and you're right - a long "on" of the airbag light is the airbag module, supposedly.

I would first unplug the negative terminal of the battery and hold the brake pedal down for 20 seconds, then try it again and see what you get. Could just be a gremlin. If it isn't, I'd find a good used one and go from there.

Dale

and gutsy (darwin) award of the year goes to the guy driving around with a airbag module that has a jumper wire in it. seriously get a used one i will sell you mine if you like...

Dale,

First, thanks for sending those check valves... they fit my 1/8" ID Viton hose perfectly, occupy barely any space, and work better than the OEMs as one-way valves.

I do not believe the airbag diagnostic module has memory like the PCME, although I'm not positive about that. The fact that the light first came on for a while, then went away, then came on again and stayed on, would seem to indicate just real time sensing and display. If there were memory, I don't think it would have gone away on its own the first time.

I will try & price some used modules, if I can find them; thanks for the suggestion.

mad,

You misread me. The diagnostic module is OUT. The jumper is in the harness on the pin that drove the transistor base that fires the airbag light. There is NO power to the airbag at all, and no way for power to get there.

---- Bill

ok that souds better. sorry you lose the award. lol

Since this is a good thread for people with solid air bag lights I thought I'd revive it.
I e-mailed Dave at KDR about my solid light. His response was:

"HEy...have seen this several time...just above gas pedal there is a control module for airbag...it literaly just pukes on its own...and in the last year I have seen a bunch of these...I think it is just the cars getting older...that being said check all fuses under dash and hood...check connections at air bag controller..if all good a new controller is needed...used they are usually junk...as they come from wrecks most of the time...hope this helps..dave@KDR"

Attached is a scan of page S-4 of the "Body Electrical Troubleshooting Manual" for the 1994 RX-7. This shows a block diagram of the air bag system.

Awesome...:icon_tup:

my airbag light blinks cause its not really connected...can i still jumper whatever to turn the light off?

Yes. If you look at the block diagram illustration above, you can see that jumpering the wire harness connector pin 2A to 2B will ground the transistor's base, turning the transistor OFF, which cuts off all current through the air bag light. Once again, if you do this, do not plug that connector back into the diagnostic module, since it will ground the module's output port, and that could damage the module. Also please note that the airbag will not deploy in an accident once you remove connector #2!

where is that plug located? as i have to shut my light off also

Stole "millennm's" pic: here

You said to unplug the connector from the module first and then jumper the connector 2A to 2B to turn off the airbag light which sounds simple enough, but according to the what the module says, "NOTE: before removing diagnostic module connector(s), be sure to remove orange and blue connectors at the steering column." Did you need to remove those first before jumpering the connectors?

The blue connectors carry the firing current to the air bag's detonator, which is why Mazda wants you to disconnect that first for safety. However, the firing current to the airbag comes from terminal 2I of the airbag diagnostic module and is returned to terminal 2J. if you disconnect that, there is no way the airbag can get any electric current. Also, you would have to put back the orange/blue connector later, since the orange connector supplies the horn signal to the steering wheel.

So no, I did not disconnect the orange/blue connectors before disconnecting the diagnostic module connector. But it certainly wouldn't have hurt anything to do that.

One thing I thought about just now, is I have an aftermarket water temp gauge wired into the air bag fuse holder. First of all I wanna say that I really don't care about the air bag, so If I jumper the connector 2A to 2B to turn off the air bag light and then leave that connector disconnected like you said, would that cause my aftermarket gauge to stop working too, being that it's hooked into the air bag fuse holder, or are those 2 completely different circuits?

There should be no effect on your aftermarket gauge connection. The 10 amp air bag fuse is a power input to the airbag system's Diagnostic Module, and that power input is still there (when ignition switch is ON) if you disconnect the DM's connectors. (This is according to the airbag system schematic on page S-6 of the "Mazda RX-7 1994 Body Electrical Troubleshooting Manual.")

Did you use some sort of special tool to disconnect the connector? Because for the last half hour, i've been trying to get the connector off with no luck. I even broke off the clip that holds it together by accident in the process and it STILL wont come off. I tried prying it loose, but it looks like im gonna break something so I stopped.

I don't recall having any trouble disconnecting the connectors. IIRC, they have the "standard" locking tab which has to be pressed to lift up its other end, and then the connector pulled off. But it was a long time ago...

Idk why whenever I do something to this car it turns into a major thing lol I actually broke that locking tab by accident while trying to take the connector off. After I broke it, I figured it be a lot easier to remove...not. I't feels like somebody super glued it in there, or maby it corroded or somehow welded itself together :( On second thought, I don't think I wanna turn off the light THAT bad lol

wstrohm, thank you! I just quickly hooked up the jumper wire to get rid of my airbag light that has been blinking for like 2 years now since I removed the airbags and sensors for weight removal. I learned to ignore it and it was no big deal, but today I got to thinking I wonder if there is a easy way to get rid of it. I started searching and mostly read about how you had to unplug the bulb and unplug the module, I was thinking there had to be an easier way by sending a 12v power or ground signal to the bulb through the wires somehow, and then I found this, perfect!

So if I'm reading this correctly, you've removed the Diagnostic Module altogether. How do you retain Horn functions if the horn relay goes through the module?

Forgive me if I made a mistake, reteaching myself how to read a wiring diagram :)

Look at the (simplified) wiring diagram from the FWM in post #7 above. You will see that the horn activation circuitry bypasses the Diagnostic Module. (There is a horn wiring path through the right-hand air bag module, but no connection to the Diagnostic Module.) This can be confirmed by looking at page Z-66 of the 1994 RX-7 Workshop Manual for the complete horn wiring diagram.

Roger that. I took a second look and noticed where they come in through the firewall on the passenger side.

Currently I'm looking for a clockspring so I can properly hook up horns and the like. Just picked up an FD and noticed the clockspring ribbon cable/connector has been broken off. It's the little things!