VSS Buffer and DRAC ECM Input

[burban_kraut]

Hi,
This is my first post - I am working on a Frankenstein Suburban. 1991 Suburban body on a 1987 3/4 ton 4x4 frame. The engine is TBI running off of the 1991 ECM but the speedometer is a cable drive because the transmission and transfer case were out of the 1987. I am trying to:

a) Get the check engine light to stay off. This is because the 1991 electronic VSS input from the transmision is not connected.

b) Get the cruise control working.

Since I have a cable driven speedometer, I installed the "Green Box" VSS Buffer that will hook up directly to the cruise control (which I have from a 1987 truck) I am working on hooking up the electrical connections which are
Pink (Power)
Black (Ground)
Brown (ECM)
Yellow (Cruise Control)

On the non-electronic speedo units, the brown wire from the VSS Buffer went in to terminal 437 of the ECM. The same terminal, 437, on the 1991 ECM goes to the DRAC.

So, here is my question: Is the brown wire from the VSS Buffer the same signal as the DRAC output? Can I connect the brown wire from the VSS Buffer to terminal 437 on a 1991 ECM?

Thanks for your help!

 

[burban_kraut]

Hi,
This is my first post - I am working on a Frankenstein Suburban. 1991 Suburban body on a 1987 3/4 ton 4x4 frame. The engine is TBI running off of the 1991 ECM but the speedometer is a cable drive because the transmission and transfer case were out of the 1987. I am trying to:

a) Get the check engine light to stay off. This is because the 1991 electronic VSS input from the transmision is not connected.

b) Get the cruise control working.

Since I have a cable driven speedometer, I installed the "Green Box" VSS Buffer that will hook up directly to the cruise control (which I have from a 1987 truck) I am working on hooking up the electrical connections which are
Pink (Power)
Black (Ground)
Brown (ECM)
Yellow (Cruise Control)

On the non-electronic speedo units, the brown wire from the VSS Buffer went in to terminal 437 of the ECM. The same terminal, 437, on the 1991 ECM goes to the DRAC.

So, here is my question: Is the brown wire from the VSS Buffer the same signal as the DRAC output? Can I connect the brown wire from the VSS Buffer to terminal 437 on a 1991 ECM?

Thanks for your help!

Bump!

 

[bucket]

I do believe the cruise control uses a different pulse per mile than the speedo output from the module. These electric speedo swaps and such have always left me confused. I think you can get one of those VSS signal generators that screws inline with the speedo cable, and take care of your problems. You will get the signal that the ECM wants to see, as well as a working stock '87 speedo and cruise setup. Painless Performace or whatever they call themselves now sells them. A bit pricey for what they are though.