I've just been having a chat about the Speed sensor or VSS signal in an earlier Fiesta regarding Cruise Control.
Does your car have Stability Control or
ABS? If so, it is unlikely to have a VSS. On
ABS/ESC equipped carsm the vehicle speed is obtained from an
ABS sensor, and then fed from
ABS to
PCM (Powertrain Control Module) via the
CAN Bus, which then sends the speed over the
CAN bus again to the Instrument Cluster. On cars without
ABS/ESC, there is a VSS (Vehicle Speed Sensor) usually somewhere on the Gearbox. That VSS line then feeds direct to a pin on the
PCM, which interprets it and broadcasts the speed to the Instrument Cluster. Back in the day, the VSS itself would have fed directly to the instrument cluster, meaning you might have found it in the dashboard somewhere.
But if you have
ABS/ESC, there's a very real chance you don't have a VSS line anywhere. In the cruise control world, this means they need to be CAN enabled, and either listen for the speed on the
CAN bus, or use OBD2 J1979 standard signalling to constantly query the road speed via the
CAN bus.
But if you DID have it, it would likely be found between the transmission and the
PCM, all within the engine bay.....
Luke