Typically abs sensors consist of four sensors one on each wheel. They are to detect if all wheels are spinning at same time and that none are locked up while applying the brake. Speed sensors are typically a single sensor located in or on transmission to detect vehicle speed for your speedo and ecu.
The Anti lock Brake System, is the system to help brake in slippery conditions. There is a Wheel Speed Sensor at the front wheels, and sometimes at the rear wheels also. Another function for the Wheel Speed Sensor would be for the cruse control system.Then there is a Automatic Transmission Speed Sensor that is for like your speedometer mph.
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