Hi guys, I just took my 1983 Firebird V8 conversion project on its first trip ever, a 3 hr highway excursion. No problems at all except a check engine light that came on only occasionally. I get a code 24, VSS circuit low. I read that this code throws if the VSS reads less than 4 mph, and the engine is between 1400 and 4400 rpms, and TPS/load indicates > 4 mph operation, for more than 20 seconds.

This car is a mechanical cable speedo. The speedo works. Is the VSS one of those things they call a speed buffer on this car? Is it located up behind the speedometer in the dash cluster?

The check engine light clears every time you restart the car, and comes on about 20 minutes of highway driving later. If the VSS output was zero mph wouldn't the code throw a lot faster, or does the computer only run the VSS check periodically?

 

I don't know about the "speed buffer" part, but the VSS is attached to the back of the speedometer.

 

Thanks, I'll have to check the wiring. Is there any way to check a VSS without hooking it up to a scope?