92 GMC Vehicle Speed Sensor "Buffer" problem: Info? Chips?

[TerryKing]

Hi Everyone,

92 GMC Yukon 5.7 TBI. Throws code = "Vehicle Speed Sensor".. Dealer replaced Speed sensor on Transfer Case but code remains (After driving a mile or 2).

So problem appears to be the "Buffer" AKA "Digital Ratio Adapter Controller" (DRAC). Mine looks like this: http://www.tbichips.com/drac/DRAC 1t.jpg

I heard a couple of years ago that some chip fails on these. Anyone know about this? Can the chip(s) be identified from the GM Part numbers? I do electronics and could replace a chip IF I knew what to replace.

Any troubleshooting suggestions?

Any aftermarket replacements? Repair services?

I REALLY don't want to go to the dealer for this little circuit board...

Any comments, suggestions appreciated!

Thanks...

 

[jdyates]

Its right next to the computer inside the dash. Pull the glovebox out and its sitting right there. Try grabbing one from a junkyard.

 

[TerryKing]

Anyone dug into these?? I am looking for the pinout / wiring diagram..

I may make a replacement with an Arduino microcontroller. If I get that working it could be programmed for any vehicle on your computer.

Any pointers / diagrams appreciated!

Photo here: http://yourduino.com/docs/92YukonVehicle-DRAC--800.jpg

 

[great white]

The question that comes to mind is "why" when you can pick up another one from the scrap yard for about 15 bucks, put dip switches in for the jumpers and have it be infinitely adjustable for tire size and gearing....

 

[TerryKing]

Sure, that makes sense 98% of the time. I may do it because...

- I can, and writing the code to do the division ratios would be interesting

- The DRAC is actually getting hard to find, especially if you are in boonies like me, and online sources seem to have dried up.

- I will be adding other microcomputer and dashboard stuff as I keep this rig running for the next several years now that I installed a new crate 5.7 and tranny. I want the Vehicle Speed connection.

- Reverse Engineering can be as much fun as Forward Engineering ??

Any pointers to the pinout appreciated.

And.. can anyone point to an Engine Wiring diagram for 92 CK 5.7's?? ONLY one not in my aftermarket manual :-(

Thanks!