A vehicle equipped with a speed sensor, should not be driven without a the speed sensor connected, as idle quality may be affected.
The vehicle speed sensor (vss) is mounted behind the speedometer in the instrument cluster or on the transmission/speedometer drive gear. It provides electrical pulses to the ecm from the speedometer head. The pulses indicate the road speed. The ecm uses this information to operate the iac, canister purge, and tcc.
Vehicles equipped with digital instrument clusters use a Permanent Magnet (pm) generator to provide the vss signal. The pm generator is located in the transmission and replaces the speedometer cable. The signal from the pm generator drives a stepper motor which drives the odometer. A failure in the vss circuit should set a Code 24.