The Vehicle Speed Sensor (VSS) is a magnetic inductive pickup that relays vehicle speed information to the TCM. The TCM uses this information in order to control shift timing, line pressure, and TCC apply and release.
The VSS mounts in the case extension at the vehicle speed sensor reluctor wheel, which is pressed onto the final drive carrier assembly. An air gap of 0.011-0.062 inch. (0.27-1.57 mm) occurs between the sensor and the teeth on the vehicle speed sensor reluctor wheel as the final drive carrier assembly rotates.
The sensor consists of a permanent magnet surrounded by a coil of wire. As the vehicle speed sensor reluctor wheel on the final drive carrier assembly rotates, an AC signal is produced by the VSS. This AC signal consists of a voltage and frequency that changes based on vehicle speed. The TCM uses the frequency portion of this signal to determine vehicle speed. Higher vehicle speeds induce a higher frequency and a higher voltage measurement at the sensor. The voltage portion of the signal is used in diagnostic procedures.
Removal & Installation
4T40-E/4T45-E And 4T65-E Transmissions
- Position the vehicle on a hoist and raise the vehicle.
- Disconnect the Vehicle Speed Sensor (VSS) electrical connector
- Remove the VSS electrical harness retainer from the VSS stud.
- Remove the VSS stud.
- Remove the output VSS from the transmission case.
- Remove the O-ring from the VSS.
- Install the O-ring onto the VSS.
- Install the output VSS into the transmission case.
- Install the VSS stud. Tighten the stud to 8 ft. lbs. (11 Nm).
- Install the VSS electrical harness retainer to the VSS stud.
- Connect the VSS electrical connector.
- Lower the vehicle.
Check the Vehicle Speed Sensor/Output Speed Sensor (VSS/OSS) as follows:
- Disconnect Vehicle Speed Sensor (VSS) electrical connector from sensor.
- With a digital mutimeter check resistance between pin A VSS low signal and pin B VSS/OSS high signal.
- Sensor resistance should measure between 1,650-2,200 ohms at 20°C 68°F.
- If resistance reading is not as stated suspect faulty VSS/OSS sensor.
- With a digital mutimeter check voltage between pin A VSS low signal and pin B VSS/OSS high signal.
- Safely lift wheels off of the ground and run in gear to check voltage readings.
- Check for output voltage this will vary with vehicle speed from a minimum of 0.5 volts AC at 100 RPM to 200 volts at 6,000 RPM.
If no voltage reading is present suspect internal transmission problem or faulty VSS/OSS sensor.