Code 26 SIR

[Betsey 2]

Please help!
Can't clear code. Both service manual and Jay Meeks methods used to clear codes. It will clear for approximately 30 seconds and comes back as a hard fault.
R/H Sensor has been removed. Frame cleaned to the metal. Sensor cleaned to the metal. Installed, torqued as per manual, and tested with and without di-electic grease.
On frame and off frame omh meters reading are the same for each test.
1 and frame .2 omhs
1 and 2 10.1 omhs
1amd 3 10.1 omhs
2 and 3 .2 omhs
Connector cleaned (yellow conector) below glove box and cabin side of the firewall.
Battery disconnected over night. Reconnected and tried to clear code. Same thing clears approximately thirty seconds and hard fault again.
I have tried the wiggle test but unable to clear fault long enough to confirm a wiring issue. I don't think it is wiring.
Service manual tells me to replace DERM if it passes omhs and wiggle test?
Questions:
1) Should I replace the sensor? Where can I purchase a replacement Sensor? I haven't checked the dealers yet.
2) Should I replace the DERM? Looks like a major job to get to it? Is it as hard as it looks?

 

[Hib Halverson]

I disagree with your belief that it's not wiring. Most faults are wiring and connections and not hardware.

If the system won't operate long enough before setting a code to do the wiggle test then you'll have to troubleshoot the wiring another way.

Once you determine it's not wiring/connections then move-on to the sensor or DERM issue.

On second thought, I'd check parts abailability, first. A lot of that old C4 electronics stuff is discon. If you can't get the parts then troubleshooting is a waste of time.

 

[gmboileau]

Hi

I went through a similar problem with Code 16(LH side sensor) I cleaned and torqued everything and still had no luck turning off the warning INFL REST lamp. I was convinced it was the DERM but once I saw where it was located and the difficulty in getting the right part and also worrying about triggering the Airbag I decided to check things again.

I discovered that clearing the codes for the Sir system is tricky because you have to ground and unground the K terminal on the ALDL connector in a specific order for very specific times to clear the codes. It’s awkward to do this ground/unground process because of the location of the ALDL connector.

I suspect you have fixed the problem by cleaning the corrosion off the sensor because the OHMS readings are in range but the codes have not been cleared properly. The clearing code sequence is:

1. Turn ignition off.
2. Ground ALDL terminal K
3. Turn ignition on.
4. Wait for fault codes to flash about 5 secs. When the codes begin flashing, unground terminal K for 3 secs +/_.5sec
5. Ground again for 3 secs. +/_ .5sec
6. Unground terminal K and wait 10 secs.
7. Ignition off



In order to make it easier to access the ALDL terminal K and to control the on off time I used a length of wire and a standard household light switch between the K terminal and ground. Just flicking the switch made it much easier to control the ground/unground sequence. Since the tolerance is only .5 sec either way a stopwatch is handy as well.

Cheers

Gary

 

[Betsey 2]

Thanks Hib,
I have confirmed the wiring to the sensor. Getting to the DERM to disconnect the wiring and back pin the wiring looks like a major job. I like the idea of comfirming parts availablity before continuing.

 

[Betsey 2]

Hi Gary,
I will try the switch idea and get a stop watch on it. I have tried connecting and disconnecting at the seat frame. It looks as if it clears but goes to 12 then back to 26. I will let you know if the switch thing works.

 

[Betsey 2]

Hi Gary,
It worked! The switch and stop watch technic was a success. It's hard to believe that that a car computer, would be so time sensitive.
Thanks

 

[gmboileau]

Hi

Always a bonus when things work out!!

Why GM made the code clearing process so difficult is beyond me. A sequence had to be programmed into the computer to do the job but they didn't have to make it so fussy. A tolerance of a couple of secs would make it much easier.

Cheers
Gary