The transmission output speed sensor is a permanent magnet surrounded by a coil of wire that is mounted to the transmission rear housing in 2WD models and on the transfer case on 4WD models. The vehicle speed sensor is positioned next to the gear that is splined to the transmission output shaft in 2WD models and next to a gear on the transfer case output shaft in 4WD models. As the gear rotates, the tips of the gear teeth cross the magnetic field which generates an AC current. The voltage output and frequency generated by the sensor will vary as the speed of the gear changes. The vehicle speed sensor signal wires are twisted to cancel magnetically induced fields. The transmission control module (TCM) changes the speed sensor analog signal into a digital signal.

P0721

P0722

P0721 Condition 1

The DTC will set if an unrealistic change in output speed is observed.

P0721 Condition 2

The DTC will set if a noisy turbine speed signal is detected.

P0722 Condition 1

The DTC will set if an unrealistic change in output speed is observed.

P0722 Condition 2

The DTC will set if the TCM detects an unrealistic low value of output speed when the turbine speed is greater than 1050 RPM.

You will have to drive the vehicle in order to experience a condition.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 38522 Variable Signal Generator

1. Perform a road test while observing the Transmission OSS parameter with a scan tool. The Transmission OSS parameter should increase and decrease steadily as the speed of the vehicle changes. Refer to Road Test.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Note: You must perform the Circuit/System Verification first.

1. Ignition OFF, remove the vehicle speed sensor connector.
2. Connect the J 38522 generator to the vehicle speed sensor circuit, terminals A and B.
3. Adjust the J 38522 generator to 30 V, frequency to 1K Hz, and duty cycle to 50 percent.
4. Ignition ON, engine OFF, use a scan tool to verify the Transmission OSS parameter is between 1450 to 1550 RPM.

⇒	If not the expected value, check the vehicle speed signal and ground circuits for an open/high resistance, short to ground, or a short to voltage. If circuits test normal, replace the TCM. Refer to Control Module References for TCM replacement, setup, and programming.

5. Test or replace the vehicle speed sensor. Refer to Speed Sensor Replacement for 2WD models or Vehicle Speed Sensor Replacement for 4WD models.

Static Testing

Note: You must perform the Circuit/System Testing first

1. Ignition OFF, remove the vehicle speed sensor. Refer to Speed Sensor Replacement for 2WD models or Vehicle Speed Sensor Replacement for 4WD models.
2. Test for resistance between terminal A and terminal B of the turbine speed sensor. See Speed Sensor table, refer to Temperature Versus Resistance for 2WD models or 1,420-2,140 ohms for 4WD models.

⇒	If not within the specified range, replace the speed sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

If another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.