DTC 24, VSS Circuit Low (Transmission 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 40 pulse per revolution signal to PCM.

DTC 24 will set when:

• Gear selector is not in Park or Neutral.
• Trans output speed circuit voltage is constant.
• Engine speed is greater than 3000 RPM.
• Output speed is less than 250 RPM.
• MAP is less than 100 kPa.
• Throttle position is 10-100 percent.
• All conditions are met for 3 seconds.
• DTCs 21, 22, 28, 33 or 34 are not set.

PCM will default to 2nd gear only at maximum line pressure.

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.