Cutlass V6-260 4.3L DSL (1984)
Vehicle Speed Sensor: Testing and Inspection
Vehicle Speed Sensor Check VINs T and V
Fig. 046 - WIRING DIAGRAM for Vehicle Speed Sensor Check. VIN T, VIN V
VEHICLE SPEED SENSOR CHECK (VSS)- DIGITAL CLUSTER
Vehicle speed is sensed by a Vehicle Speed Sensor located behind the I.P. cluster. The VSS is supplied with 12 volts from ignition and ECM. The
output from the VSS to the ECM is a "toggling" of the voltage. As the speedometer turns, the 12V signal from the ECM is turned "ON" and "OFF". The
faster the vehicle speed the more rapidly the signal toggles. This VSS input into the ECM is used to calculate amount of EGR and also TCC engagement.
The VSS will turn "ON" a CEL only if the ECM does not see a VSS signal for at least 26 seconds under an MVS load of from 25%-50%. The CEL
will go "OFF" as load falls below 25%. The light will come back "ON" if load exceeds 25% again for at least 10 seconds. Thus, a VSS generated CEL is
load sensitive and will go "ON" and "OFF" with load.
