DTC 72, Speed Sensor Circuit Loss (Trans Output Speed Signal): Notes

Vehicle Speed Sensor (VSS) circuit consists of a magnetic induction type sensor, VSS buffer module, 4WD low switch (if equipped) and wiring. Gear teeth pressed onto output shaft induces an alternating voltage into sensor. This signal is transmitted to VSS buffer module. VSS buffer module compensates for various final drive ratios. VSS buffer module will also convert AC VSS signal into a 40 pulse per revolution DC signal on trans. output speed circuit to indicate transmission output speed. On 4WD vehicles, 4WD low signal will also be used for adjustment of the 40 pulse per revolution signal to PCM.

DTC 72 will set when: 

Gear selector is not in Park or Neutral.

• Transmission output speed change is greater than 1000 RPM.
• Engine speed is greater than 200 RPM.
• All conditions are met for 2 seconds.
• DTC 28 is not set.

Or 

Gear selector is in Park or Neutral.

• Transmission output speed change is greater than 2050 RPM.
• Engine speed is greater than 200 RPM.
• All conditions are met for 2 seconds.
• DTC 28 is not set.

PCM will default to a soft (delayed) landing to 2nd gear and 2nd gear starts.

1. This test checks for voltage to VSS buffer module.
2. This test checks ground circuit to VSS buffer module.
3. This test checks VSS circuit at VSS buffer module.
4. This test checks for an output speed signal from VSS buffer module.