GMECM Digest V1 #160 (VSS / DRAC)

[Jim Sloan]

> Hi I'm hoping some one can give me some info.I'm building a pulse
> generator
> with a 555 to make aake VSS signal. I order to feed this signal to the ECM
> do I have to go thru the DRAC (its a 7749 Syclone computer) or
> can I feed it
> directly to the ECM?

According the the Syclone Service Manual, " The DRAC processes inputs from
the VSS and output signal to the speedometer, ECM, and cruise control
module. The DRAC takes the voltage pulses from the VSS and uses them to open
and close four solid state output switches to ground at a rate proprotional
to vehicle speed."

This makes it sound like you need the DRAC. Of course, the service manual
has been wrong before.

Jim Sloan
leroy at sunflower.com
Syclone VIN# 1206
http://www.sunflower.com/~leroy
Lawrence, Kansas