I did some work on the car and had to unhook my dakota digital, I hooked everything back up and now the speedometer is hugely off. For instance, backing out of the driveway reads 50mph, and just starting out in first gear pegs the speedo to the max speed. I'm not sure what could have happened. Im just looking for ideas on what i should check. It almost seems like the PPM is off, could i have blown or shorted my dakota digital unit?

 

If you are certain you have it wired correctly (triple check), go through the setup sequence again and see if it works, if not you probably fried it.

 

I have gone though the wires a few times and am ruling things out. What i dont understand is how it could be off so much if hooked up in any way where its reading a signal. I'm thinking the unit is shorted and is acting like a pass through. From what i understand, the t56 is 8000PPM and the speedo needs 4000ppm. It seems like the speedo is seeing 8000PPM even though the SGI-5 is hooked up. Thats the only thing i can think of which would cause the speedo to read so high. I think im going to bypass the dakota digital unit and see if it reads the same way.

 

Why not use an oem buffer box give it 8k input ang get the 4k off the ecm ir cruise output (4k if maf ecu otherwise it gets full signal)

 

Looks like im going to have to dig into this more. This car has been in the family a long time, and my bro did the wiring over 10 years ago. I'm going to have to see if hes wired to the buffer box, i think he is, since the odometer does work and if i recall correctly, the odo has its own output from the buffer box.

 

17 tooth pulse per driveshaft revolution is several times more than 4004ppm, not double.

It does sound like it could be a wire could be hooked up different. That's an easy enough test to move a wire from 8000 out to 2000 out, for example. Or, the revision you have, might use this manual, for reference: http://www.dakotadigital.com/pdf/sgi-5c.pdf