The Fiero cluster that three connectors. The one on the left side, (facing forward) underneath the cluster plugs directly into the speedometer board. That connector has an "M" pin that is only on the 88 that has the square wave on it.
Some say the "N" pin also has it, but that is not my experience. I have found the 4000 ppm on the GT boards, but I had to probe around for it. I have not found it on the 4 cylinder boards at all.
As for the speedometer board (84 non cruise, 85-88):
A - not used
B - not used
C - not used
D - not used
E - not used
F - not used
G - not used
H - not used
J - not used
K - not used
L - not used
M - 4000 pulse per mile buffered VSS (88 only)
N - 4000 pulse per mile buffered VSS (86-87) ?? per Gary W
P - black/white - ground
R - puple/white - from the VSS (low)
S - Yellow - from the VSS (high)
T - yellow/black - Ignition power to cluster
U - Dark green/white - 2000 pulse per mile Vehicle speed sensor signal to ECM and Cruise
I hope that helps??
[This message has been edited by jscott1 (edited 09-21-2006).]