Vehicle Speed Sensor/Transducer - Cruise Control: Description and Operation

DESCRIPTION
On front wheel drive vehicles the speed sensor is mounted in the transaxle. A magnet rotates near a coil, producing voltage pulses in the coil. As speed increases, so do the number of voltage pulses per second.

OPERATION
The speed sensor buffer takes the sensor/voltage pulses from the sensor and uses them to close two solid state output switches. Each output terminal is switched to ground at a rate that is proportional to the speed of the car. The speedometer and the ECM are switched at 4000 pulses per mile. The output switches in the speed sensor are solid state. Self-powered test lights or ohmmeters should not be used to test them. Do not measure the resistance at the outputs of the buffer.