UNCLEBILL

I have a 1990 Vert with 14,000 miles. Started it today and both lites came on and stayed on. Did a search and then checked for codes. No codes showed up with my Auto XRay scanner or the plug in code reader...just kept blinking a code 12. Tomorrow I will start with the sensor on the passenger side to clean (as the search results indicated). The thing that bothers me right now is the fact that in doing the search; codes would be thrown for either left or right side sensor but I show NO CODES. I was able to see the sensors(just barely) and the bolt down area looked clean and no rust but will clean and grease as the search indicates.Am I missing something in my search where NO code is shown and if my preliminary observation on the sensors show no rust...where do I go Next?
I would appreciate any imput into this matter.
Thanks
Bill
I just retired and have the time to do it but hope for no big $$ cost.

cv67

Youre starting in the right place. 90s are notorious for that stupid light coming on all the time.

abc 123

Neither one of those instruments will read the SIR system.

Ground A-K on the ALDL and get the codes.

UNCLEBILL

Thanks for the heads up on why I could not read the codes. I have a question... my researching show that to find codes and clear codes that I use the "K" terminal....... you are suggesting that I use the "A" terminal as my ground while the searches say ground to seat bracket--does this "A" -"K" terminal hook up not simulate the code reader? I will do it ALL ways just to play it safe but was curious about this one.
Wow; since I bought my Vette last year the things that I have learned so far on this forum are Mind Boggling!!!
Thanks to all for the help so far

abc 123

The A terminal on the ALDL is always the ground. B terminal is what you use to get into the SES, C into the SRC.

So when you ground a paperclip across A-K, you enter the SIR function, INFL RES light will flash and give you the codes that are stored. Nore than likely it will be a 16.

UNCLEBILL

Tried a few times and it starts up with a code 12 then gives a code 26 from then on. At least I know now its the passenger side sensor and hope the clean and grease will work as I can just barely see the sensor (code 26 it seems is a sensor fault--hope not) and cant see any rust but will start the disaaembly tomorrow. Just have to walk away from it today as I have had several annoying little things happen lately..I fixed them but the research can be demanding.

UNCLEBILL

Well I cleaned the RT sensor per instructions...no good...pulled the sensor completely out of vette and checked ohm resistence as per FSM (4 variables) ALL showed okay..the sensor is GOOD..just for the heck of it I checked with the dealership and not one sensor showed up in North America.After all this I still cant clear code 26. I made an error and was not patient with the error code reading...3 times code 12---3 times code 26 AND a new one..3 times code "41" then back to code 12 !!!!! It looks like the DERM may be the problem or hopefully just a short circuit which possibly affects the code 26 also??.Will look at this tomorrow but I have a disc gone in my back and I didnt retire to hurt more...I may just live with the warning displays as I dont think I want to get under the drivers side dash. Will decide tomorrow I guess.

Allentown Ernie

I have the same problem with my 90 coupe. code 26, last summer I did the sanding thingy, and dialectric grease on the right sensor and then cleared the code. This summer it came back so I cleared the code again. Last week the code 26 appeared again. This time I have been unsuccessful in trying to clear the code. I suspect checking the ohms will indecate a good sensor as well but I have not done that yet. What is the derm and where is it located? This problem is a PITA. By the way when I worked on the sensor there was not a bit of corrosion between it and the frame. Just want to rant a little because of this problem. Have a great day. Allentown Ernie.

UNCLEBILL

The DERM is a diagnostic module under the drivers side dash.If it is the problem; its supposed to throw a 52-54 code. I pulled the sensor out (right side) and checked it with a multimeter OFF the car. It read all 4 checks okay. DO NOT CHECK sensor with multimeter when sensor is on the car....even though you disconnect the battery; the batteries in the multimeter can set off the airbag as per FSM. I threw a code 41 also...I would have to check for shorts from sensor to DERM...if none; then FSM states you need a new DERM (Diagnostic Energy Reserve Module). Before I tear everything apart(including my back) I went to the dealership to check for this module...discontinued and none showing up across N. America...PLUS the cost was $1300.00 CDN IF there was one . There are no new sensors or DERM's left new to find so all this is for the airbag...I am going to just pull the consul and seatbelt bulb and get on with life. NO parts for a SAFETY related part...go figure.
By the way; thanks for letting me rant also!!!

Kleantouch

I had the same problem, but instead of going thru all the troubleshooting, I bought a plug/switch from midamerica designs for $20, hooked it up, followed the directions and the lights went away. Don't know what it did, but they're gone.

UNCLEBILL

I made up my own using a small short throw toggle switch. It seems that exact timing is important....3 sec. on---3 sec. off--10 sec on then off. tried and tried probably 2 hours but I think that besides the code 26; I was also throwing a code 41 that may be impairing the code clearing...dont know for sure anymore..down the road Im just going to pull the seatbelt lite bulb and the INFL. REST. BULB AND CALL IT A DAY.

pipe

A code #26 is the right front sensor fault. Sometimes cleaning & sanding won't fix it. But before doing any work on them DISCONNECT THE BATTERY!!! If the codes won't clear then your sensor is faulty. Check the pin connector in the footwell area with an ohm meter on the pins. The factory service manual will tell ya the sequence and ohm specs. Not very often does the DERM go bad. You will need to peel back the carpet in the footwell area to get to the yellow barrel connectors. Let me know I can help some more. Pipe

UNCLEBILL

I did that (the pigtail to the sensor)...there were 4 variables--2 with less than 1 ohmn and 2 with 10 ohmns...I was right in line with the FSM.This is why I turned my attention to the DERM. The code 41 had me bothered. The FSM stated that if no shorts to it; replace the DERM.Im not an electrical wiz and Im starting to get a bit frustrated....its hard for me to crawl into the footwell areas due to my back problem (and age maybe).Ive learned alot in the past while on this project but not seeing any results. I would like to get to the bottom of this project but seem to be a bit lost now.
Any help would be appreciated to solve this problem as I have the time now since I retired. I want to walk away from this problem one moment but my stubborness keeps me going to fix it.

Churchkey

Cannot help with electrial problem however if you put the car up on jackstands its alot easier to work under the dash. My back is also a bit of a problem.

pipe

Your almost correct 3 variables. 2 at 10,000 ohms and one with less than 1 ohm. A code 41 is indicator lamp circut, shorted to battery or ground.The DERM is a pain in the azz to get to. It's good you are persistent at fixing this problem and not just going to pull the bulb out of the driver info center. I know it's tough getting under that dam dash. Ya gotta be double jointed. This kinda got me stumped as usually it's the sensor. Pipe

UNCLEBILL

oh boy....did not take a close look at the dwg in FSM and misread the Derm being under the driver side dash. It was the cable to Derm that I saw. My 4th check was the #1 to chassis grd(took a chance).Thats it; since its behind the radio that will be a pain in the azz!!! The whole thing about this subject is that it doesnt affect driveability and wont activate. Im pulling the bulbs for now and getting on with life. I may go back to it at a later date(maybe) but have spent the last several days on this project and need to just drive my Vette now.
Thanks for all the help..it kept me going . Will be back when and if I get back to this project.

gmboileau

The left and right sensors have the same part number so I wonder if you could switch the sensors form one side to the other, clear the codes and then see if the problem changes to the left side (code 16). This would indicate a bad sensor. If you get code 26 then I guess the problem is in the wiring from the sensor to the derm or the derm it's self. In any case the results could give you additional clues as the source of the problem. Code 41 seems to be involved with the light once it's on so if could eliminate your code 26 then code 41 might take care of it's self.

UNCLEBILL

Thanks for the idea. Did a rank in my previous post due to frustration. The Vette is being put away in the next few weeks so I will have all winter to play around. Im retired now so I will have plenty of time to look at it. I just have to walk away from it for a brief time and get my crusing in before storage time.
Thanks again to all that posted and gave me ideas and advise!!!!

WVZR-1

I believe if you're not concerned with the "functionality" of the SIR a 2 ohm resistor at the connector to the bag or at the base of the column will defeat the "bulb on"!

It will also allow the 'belt warning" I believe to funtion properly.

UNCLEBILL

Thanks; if all fails at least I will have a alternate route.