I have a 1990 Corvette. The "infl rest" and the seat belt lights do not go out. I was told by the GM dealer to replace the SDM unit. That's that orange thing under the radio. HOW DO I GET IT REMOVED? It looks like that's the first thing the assembly plant installed before the dash, etc.
I appreciate any help you can provide.
Larry Rice

 

There's much to check on a '90 before just doing the DERM/SDM - do you have a list of the faults for the SIR that caused their "suggestion". Not sayin that it's NOT the DERM/SDM but there's much to do before just doing it.

 

Replacing the DERM is a big project. It has a number of wires going to sensors and power sources etc.

Careful diagnosing of the problem is really important. As WVZR-1 has suggested you need to know the fault codes before proceeding with any repair.

 

It all started with my disassembly of the speedometer and hvac controls to have them repaired. That work is done, but now I have the infl-rest and seatbelt light issues. I disconnected the yellow connector to the airbag, but didn't put any load tool in the system during the repair process that took several days. I think that is what caused my dilemma. My Chilton's book doesn't provide any info on this project. It looks like the large plastic skeleton must be removed, or the metal supports, maybe from the passenger side, to get to the SDM. I don't get any trouble codes.

 

Who's done the diagnostics that you feel indicate that the DERM/SDM requires replacement/ There's diagnostics involved and there's known issues with grounds ec in the '90 SIR system sensors. Your Chilton I doubt helps much at all. Judging from your comments you don't have the HELM/GM FSM for the car. Do you?

Are you familiar with the GM TSB's for the '90 SIR? There's a few with very specific diagnostic procedures.

 

The dealer suggested the cure to my problem. You are right, I am in the dark for doing any other diagnostic tests. The Chilton's book is little more than an idiot's manual. I think I will look for some bad ground wires if I can see where they are located. I could just put a happy face over the infl-rest light. (or remove it).

 

If you're not concerned with the operation of the SIR you could likely just use a 2Ω resistor at the column base or top of column under the bag and put out both lights. It's much easier to do a resistor than to remove bulb(s). Resistor needs to be 2Ω and a 5% should work. You might try for a 1% but no greater than 5% and nothing other than 2Ω specific.

 

I assume that the resistor is connected to each side of the air bag wires? In other words, this item puts a load on the air bag system, correct?
Thanks for your assistance.

 

Does this have to be a "power resistor" with high wattage or just a normal 1/2 watt resistor?

 

I'm quite sure mine are 1/4 watt or 1/2 but I have seen 5 watt also here in the C4 section mentioned.

 

if you replace the resistor, you may put yourself in a bind if you ever sell the car or someone else ever drives it thinking the airbag is in working order and something happens and it doesn't deploy. Signing a waiver means nothing or letting new owner know. I am not a lawyer and this is not legal advice.

 

http://www.corvetteactioncenter.com/...vised-561.html

https://www.corvetteforum.com/articl...990-corvettes/

 

This is good information, I just didn't have a link to it. I know Gordon Killebrew and I talked about the problems with the 1990 SIR being problematic.

 

All this talk about Resisters? If you could turn out the light with a resistor at the column base NOT RECOMMENDED the problem probably lies in a open in the airbag coil reel, it's a wire that goes up column and has a 1/2 a Dozen turns at the top to allow a direct link with airbag while turning the steering wheel.

to test is fairly easy disconnect the both ends upper (airbag)and lower column and do a continuity test.

 

 

Just to understand, was this not an insurance claim? If so they should have paid for repair. Did you but it back as salvage? Again, just trying to help. The clockspring is required to be replaced after driver airbag deployment , even if it tests good. Let us know the details and you will get all the help you need!

 

 

You joined a '90 thread and there's many differences SIR system.

Did you resolve the frame repair questions? Did that turn out to be something minimal like a broken engine mount?

SIR coil doesn't 'require' replacement on deployment. It generally was just because no insurance company could/would deny you 'if you asked'. It's often suffered heat damage and the '90 very seldom survived. Most often the connector was melted. '91 and later coils seemed to survive. It seems you understand the diagnostics.

Regarding 'legalities' - that's a very weak argument for any discussion. Do you trust a 27 year old SIR? I've seen people hurt badly from early deployments. He!! GM and others actually had order options where 'side curtains and anything other than steering wheel and occupant dash panel SIR' could be eliminated from the build. Many rental car companies got much flack regarding these builds not many years ago.

Driver SIR defeat - I see no issues and I've seen in Virginia cars with both bags deployed and 'cut away' pass safety inspection. I was shown one after an inspection by a VA Trooper at an Inspection Station where they wouldn't inspect and the owner called 'the law'. Is it still a valid law? No idea but this was in '97 for a car repaired less SIR (customer request) in a large collision shop. I had no part in it!!

I saw the car with SIR cut away and a valid VA inspection!!

 

You are wrong about legalities. Not going to debate it here but don't want anyone reading this thread and think otherwise. As far as rental companies ordering cars without side and head airbags, that's fine, they are not there but if they are there, someone is on the hook for them working and also not being replacement covers only.
This I am sure of. You cannot sign a liability waiver either, anyone who rides in the car in the future didn't sign the waiver, nor anyone you sell the car in the future to, plus anyone that drives the car now or anytime in the future (service shop, valet, etc) . The person who knowingly disabled the warning light to an SRS to appear working is on the hook until the car is crushed, even if they sold it years ago.