My '89 Firebird Formula is occasionally turning on the Check Engine Light, and spitting out Code 24 which is "Circuit Fault in VSS". I know in the Fords that I've dealt with from that vintage that the VSS is just pretty much used for the cruise control, which my Firebird doesn't have. I suppose it could also be running the speedometer if this is an electronic one as opposed to mechanical (anybody know?). Anyway, could this sensor be affecting my car in any other way?

 

Yes the VSS runs the speedo; it also tells the ECM how fast the car is going, so it knows if it's time to apply the torque converter clutch or not.

IIRC there's a VSS buffer in Firebirds that conditions the signal for the ECM, which if it fails, the speedo itself will still work but the ECM won't get its copy of the signal, and that it's a frequent cause of problems like this in the Birds. You might want to check that out.

 

I thought that the 700R4 was a fully mechanical transmission, meaning that it doesn't even communicate with the ECM.

 

OK..... but the 700 doesn't think so.

The transmission itself is hydraulic. However, the lockup clutch is electrical and is driven by the ECM.