1981, stock with all CCC parts on and operational.

Once in a while I am getting a Code 24, Vehicle Speed Sensor. I know this is mounted behind the speedo cluster and I believe works off of a spinning reflective wheel or sort to get it readings and send series of pulse voltage to the ECM to determine the vehicle's speed......am I in the ballpark?

Should I get a Code 24 while engine is running, parked and not going down the highway?

Any thoughts, comments, idea will be great and thanks in advance. I have the '81 Service Manual and also the CCC Service Manual and see the troubleshooting chart, just haven't jacked the vette up yet to start that process.

|UPDATED|6/19/2012 4:09:40 PM (AZT)|/UPDATED|

You could set a speed sensor code by just turning the key on, without starting the engine, IF there is an electrical issue, such as a short to power, or a short to ground, or an open, in the sensor circuit.
I'm not sure about a speed sensor on the dash cluster...I show the speed sensor mounted to the trans, but, regardless, it has a 3 wire connector...an 8 volt signal from the ECM(ecm terminal #19) on the light green w/black tracer, and the signal return TO the ECM on the dark brown wire(ecm terminal #16). The other wire in the connector is a ground.

The VSS is built into the speedometer in 1981-'82. Some 1980's w/California 305.

There was a service bulletin on Code 24 back in 1981.

1:With the ignition on, engine off, probe pin #16 of the ECM with a volt meter. Raise one wheel and rotate to observe for varying voltage.

2:If no voltage is observed, the connection between the IP harness and the VSS buffer amplifier must be disconnected. Then the pin to pin voltage checks can be made of the IP harness connector to determine any problems with the IP harness.

3:If ok, check VSS connector.
4:If ok, replace VSS assembly

5:If the condition persist, the speedometer must be returned to an AC Delco account authorized to repair speedometers equipped with VSS.

I hope this info helps out.

Sarge