Output Speed Sensor Circuit (4WD): Notes

Fig 1: Output Speed Sensor Circuit Diagram (4WD)

Courtesy of GENERAL MOTORS CORP.

The speed sensor, which is a Permanent Magnet (PM) generator, provides PCM/TCM with vehicle speed information. PM generator, mounted in transfer case, produces a pulsing voltage signal whenever vehicle speed is more than 3 MPH. Voltage level and pulse increase with vehicle speed. Control module uses this signal in calculations to determine vehicle adjustments.

1. This step tests for voltage variation while wheels are turning. Voltage will be low at low wheel speeds (4-6 volts at 20 MPH).
2. This step checks output speed sensor signal.