Derm Module

I have a 97 Chevy Blazer LT. The airbag light has been staying on all the time so I brought it in to the local GM Service Dept.

Tech. told me they have to replace the Derm Module. He quoted me $630 parts and labor. Is this fair? It seems really high.

OR...Would this be something I could do on my own? If anyone has info. on how to replace a Derm Module PLEASE HELP!!!


Thank you so much for your help,

Angelo

This device is often refered to (incorrectly at that) as the "black box". The DERM mdule has three functions:

1) Determines how and when to deploy airbag(s) and at what velocity. (On newer vehciles beyond 2004) It also "Stores" a small amount of current (up to 15 minutes, standby capacity) in the event of battery failure in a severe frontal collision, still allowing deployment of airbags and logging of data.

2) Records "near collision" data, and retains this for 250 Key on, key off cycles. (It can tattle on you being an agressive driver if the data is pulled from it within this time period!)

3) Records *permanently* the last 5 seconds of information up to a collision and airbag deployment. It records at it's most basic level, Throttle position (percentage of Wide open throttle), Wether the brakes were applied or not at the time of colision, vehicle speed, and engine RPM. If the vehicle was rebuilt from a crash, this module would have to be replaced as it remains in a permanent EPROM flashed state from the last accident it recorded.

In 1998 and later Blazers, this module is located under the center console on the floor. Data is fuzzy/nonexistant on earlier models that I am looking for at the moment. Following GM's logic though, I would say to look for it under the passenger seat, or all along, under the knee bolster. It will be easy to spot because it will have a yellow conector on it and a yellow and silver sticker on top of a shiny aluminum box.

Try your luck at a Junkyard for locating one from a vehicle that was not wrecked. Most junk places I have gone to for various bits and parts over the years just shrug when they see a small part and say "Gimmie $10/$25 for that." It's useless to get one from a wrecked vehicle because it will most likely been "locked" with last known collision data stored and cannot be reset. You'll have to get a virgin one, or one from a car/truck that was wrecked without airbag deployment. Shopping around on E-bay and parts house specializing in airbag modules reveals a steep discount compared to the dealership quotes $600+ dollars, but - this *IS* a component you don't want to be caught out on with the wrong part, incorrect installation, etc. What kind of price-tag can you put on your safety and get this done right?

Also, beware of E-bay and Internet deals on these modules at the moment. Thousands of cars and trucks have been drowned in floods this year alone. There are businesses springing up all around that claim to clean and "reflash" these modules to "like new" condition after they have been flooded and rendered destroyed in the eyes of GM. I would rather pick one up off the shelf at the dealership, sealed, brand-new in the box, IMO.

thank you for your detailed response. looks like i am going to have to learn to live with this light on.

thanks again...

*Sadly shakes head* Don't do that, please. Especially if your truck has passenger side airbags. You will be caught very liable if a passenger suffers injury in your truck with a malfunctioning DERM. When your or rival insurance company pulls data from the serial bus leading to the DERM and find it in "fault state", they are going to eat you alive. Get this fixed ASAP, please.

Wolfox, That was very educational, are you saying I have this little TATTLE TAILER on my 98?

Yeah, according to the google info I dug up just this afternoon, it stores "near crash" data (Where recorded varibles show strong variances in vehicle velocity, but did not trigger an airbag deployment event) for 250 Key on/key off cycles or about 60 days of driving. For a new "near crash" event to be stored within that time, the near crash data is evaulated and compared to already stored data patterns. If the new data is more radical than the last, it replaces previous recordings. But always, it will store the last 5 seconds leading to a crash that deploys the airbag *permanently*. There is no means of resetting it. It must be swapped for a new unit at that point, so just repacking an airbag module into the steering wheel is not enough to restore airbag functionality. On newer models, it has the curious ability to also determine which velocity to deploy the airbag with to catch lightweight passengers, or not deploy at all. (In the case of small framed women and children/babies in car seats) It can also activate seat-belt pretentioners only, or a combination of tensioning and two different stages/rates of deployment within miliseconds of a front/near frontal collision. This is achieved through a calibrated silicone bladder within the seat cushion that measures a passenger's weight against a sensor and a stored "zero weight" profile in the ECM. It's some pretty trick technology!

thank you for your detailed response. looks like i am going to have to learn to live with this light on.

thanks again...

Learn how to disable the system but do NOT just ignore it.

It will go off with the force of a shotgun and can kill.

WOLFOX, Thanks For the Information, WOW, I did not know any of that.

Learn how to disable the system but do NOT just ignore it.

It will go off with the force of a shotgun and can kill.


All of the guys at GM said the worst that could happen would be that the airbag would not deploy in an accident. You are saying my airbag could just deploy without warning/for no reason, based on my Blazer needing a new Derm Module.

i got one from a blazer in the junkyard $15 now i can replace the one involved in the accident. i also replaced the air bag , discriminating sensors, arming sensor. everything in good condition the vehicle i got it from wasn't invoved in a crash , no vehicle damage, all for less than $50 .i recomend a manufacturers repair manual used, it is the first thing i do when i get a new used vehicle, you learn an awful lot of invaluble info to keep your vehicle repaired & maintained, remember the junkyard is a great resource often overlooked good parts for very little money.

I don't know what year it started, but you can't take DERM's out of other cars.....They learn the VIN number of the vehicle and it can't be changed....if you are in an accident and the VIN in the DERM doesn't match the vehicle, they know it was changed and taken from another vehicle....in some cases it sets a code B1001.....

In insurance cases, if they discover a used part from another vehicle used in your car, and it causes a problem, you won't have a leg to stand on....

Pre 2000 cars use a vehicle non-specific DERM, the more complex our vehicle management systems become the less we can do for ourselves, due to the high price of scan tools and the compexity of their use.since i drive the vehicle, the last thing i want is a non-functional system. i go by my manufacturers shop repair manuals only, never the poor excuse for a manual by Chiltons or Haynes.Chiltons use to produce a fine manual, it seems they just gave up producing anything worth while.

Oooooh! I know a couple someone's about to get slapped around for replying to old posts! Meh, but not by me. The original poster probably just got his vehicle a new owner. That's pretty common. Anyway, I just did what Wmurky did to my 96 Blazer last month. Worked fine, and luckily I didn't have to replace the airbag itself. Hope I don't have to mess with anymore airbag crap, but really I had all of 28 bucks into all the parts. Anyway, I'm signing off before the old fart --er, I mean older and wiser forum guru starts typing in all caps at us...

<edit> Oh, don't know if wolfox is still around the forums here, but that's some of the best and clearly stated info I was able to find when I was looking into this same issue. Hope he's still around....