Code 72, Vehicle Speed Sensor Loss
WARNING: This page is about a different car, the 1995 Chevrolet Caprice. However, it is still accessible from the selected car via links, so may be relevant.
Speed sensor, which is a Permanent Magnet (PM) generator, provides control module with vehicle speed information. PM generator, mounted in transmission, produces a pulsing AC voltage signal whenever vehicle speed is greater than about 2 MPH. Voltage level and pulses increase with vehicle speed. Control module converts pulsing voltage to MPH, which is used by control module to calculate vehicle adjustments.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- An intermittent connection at VSS or PCM may cause code to set. Inspect harness and all related connections. Check for damage or pushed out terminals.
- Ensure harness is routed away from hot exhaust components.
- If software/calibration is incorrect, code will set. Ensure calibration is correct before replacing PCM.