1990 Cadillac Brougham Digital Dash issue!

[Cadlover1990]

Hello ladies and Gents. I'm having trouble with my digital dash. Just put in a new speed sensor, and sent the Speedo it self out to be services, and it's still reading 0. So I'm on to replacing the speed sensor buffer box. Does anyone know the location of it, or had anyone dealt with this same issue? Thanks in advance!

[TJ Hopland]

I don't know that car specifically but the cars I have dealt with that had them they were usually pretty close to the main ECU.    Its a white-ish slightly clear box about the size of a cassette tape. 

They were used on a lot of GM stuff in the 90's.    The unit itself is universal but the programing is vehicle specific.   The programming is done with soldered in jumpers.   Some of the aftermarket people usually related to trucks mod them to have switches for easy programming like when you put larger tires on. 

Apparently what the thing does is converts and distributes the signal from the vehicle speed sensor to the various systems that need it.   They had not yet integrated all the systems or taught them to speak the same language.    Cruise control needed one language,  ABS needed another, speedometer in some cases needed its own signal, and the main ECU needed a signal.   

From what I have read they tend to be pretty reliable and are usually not the problem but since the systems are not integrated it can be difficult to narrow down where the issue is. 

[Cadlover1990]

Ok. Thank you!