[Gmecm] VSS Question

[Jay Vessels]

Hi there!

I don't know what MEMCAL (chip) you're using (please mention the BCC -- 
broadcast code -- which is a 3 or 4 letter string on the MEMCAL label 
like AUJP), but does it expect a magnetic VSS (4000 PPM, AC signal) or 
an optical one (2000 PPM, 5V square wave)?  The 727 and 730 can use 
either, but the MEMCAL has to be programmed to look for one versus the 
other.  It's an easy programming change (one 1-bit flag determines which 
VSS input it monitors).  If you're burning your own chips, this should 
be easy to check and change.

Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)

T & J Spees wrote:
>  
> 
>  
> 
> Hello All,
> 
>  
> 
> I am new to the group and I am hoping I might be able to get some help.  I
> have installed a TPI system running with a 727 ECM.  I have just connected a
> VSS in an attempt to get rid of code 24.  I am using a stealth conversion 4
> pulse sensor that allows the connection of the mechanical speedo cable to
> the car.  The ecm does not appear to be reading the signal from the VSS.  I
> connected the VSS to the ECM via a twisted wire pair to pins for the VSS on
> the ECM according to the schematics.  Everything else works, but I still get
> a code 24.  Also when I attempt to view the data stream with Tunerpro, the
> vehicle speed shows as zero.  I have manually checked the VSS by spinning
> with a drill, and it was producing AC voltage.  So, I expect the VSS is
> working.
> 
>  
> 
> Can anyone provide some suggestions?  Any help would be appreciated.