Circuit Operation

The Speed Sensor Circuit consists of a magnetic type sensor and wiring. Gear teeth pressed on the Transmission Output Shaft induce an alternating current in the sensor. This sensor generates a sine wave output with a frequency proportional to vehicle speed. The Powertrain Control Module (PCM) converts this signal to an output that is switched to ground at a frequency of 4000 pulses per mile at the DK GRN/WHT wire (CKT 817) which feeds the Turn Signal Alarm, Power Steering Control Module, Instrument Cluster, Cruise Control Module and Radio (Chev only).