Trying to figure out why my speedometer doesn't work.1988 Fiero GT Getrag 5 speed. 4.9 Caddy carburated and single wire HEI distributor. for this to work does it need the origional ECU? It appears to be wired but I just got this car and it is kind of crude on the wiring in the engine compartment.

At the tranny there is a VSS, vehicle speed sensor. It has two wires on it, Purple, and Yellow. On an automatic its on the farthest right part of the tranny. On a manual its near where the axle enters the tranny. Can you follow where those wires go? If a manual do they both go to the ECM and to C203 in the armrest?

C203 is where the signal runs to the speedo. On a manual, if an original transmission, the signal can just be split from the VSS and one leg ran to the ECM and another to the speedo.

[This message has been edited by phonedawgz (edited 05-31-2021).]