Most new Vehicle Speed Sensors are of the permanent magnet type, and function much the same as a camshaft or crankshaft sensor. The sensors can be mounted either in the transmission case or rear differential assembly. Those in the transmission are typically gear driven and those in the differential function by using a trigger wheel mounted with the ring gear. Both style sensors perform the same task. Driveability symptoms caused by a faulty sensor can vary greatly due to the number of tasks the sensor output is involved in. Most vehicle computers will set related check engine light codes for vehicle speed sensors that malfunction.