92 Lesabre - Code 26 No Cruise/No High Mount Stop light

[cyntax01]

Hopefully someone can explain this problem I am having with my 1992 Buick Lesabre Custom.

A while ago I noticed that my Service Engine Soon light was coming on intermittently, I checked the OBD and it reads code 26 which I assume is the Quad Driver Module fault.

Reading about QDM's, it is my understanding that each QDM is on the PCM that can control up to 4 devices, acting like a circuit breaker.

I have unplugged my battery to reset the codes several times and this one just keeps coming back at me.

My question is what devices do the QDM's control, and what, if any would cause the following symptoms:

Around the same time as my SES light coming on I noticed that my Cruise Control no longer engages. I've read about Cruise Control systems and found that if my high-mount stop light is blown, the cruise control won't engage because it uses the high-mount stop as the brake signal.

This got me curious and low and behold the high-mount stop light just plain isn't working. I changed the bulb and it still doesn't work. I've checked every fuse block from the drivers side to the passengers side and under the hood and none of them are blown, so my only assumption is that the QDM problem has something to do with the high-mount stop not functioning.

Does anyone know what the QDM's control and what would have an effect on the high-mount stop, and what can I check to get the light functioning again and the code gone?

Everyone says not to immediately replace the PCM if the QDM is failing because more than likely it is a device that the QDM is controlling that is at fault.

I haven't noticed anything other than the high-mount stop and the cruise control not functioning, so hopefully someone can shed some light on this matter.

Thanks in advance for any help you can provide.

[cyntax01]

anyone? :-/

[Jed Rule]

I have a 1995 manual. It shows the cruise/brake switch feeds the turn/hazard switch and also a separate circuit to the 3rd stop lamp. It's on the same fuse as the hazard flasher. It shows a white wire coming out of the brake switch with a splice to the 3rd stop lamp and also a feed to the EBTCM ( Electronic Brake and Traction Control Module).
Don't see any connection to the PCM. Hope this helps.

[cyntax01]

Thanks for the info. I'm going to take a look at it tomorrow.