P0722

DTC P0721 or P0722

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC P0721
- Output Speed Sensor Performance

DTC P0722
- Output Speed Sensor Circuit Low Voltage

Circuit/System Description

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. The TCM uses the output speed signal for shift pattern. The TCM communicates the output speed to other modules which use the signal to determine vehicle speed.

Conditions for Running the DTC

P0721
* DTC P0716, P0717, P0721, or P0722 is not set.
* A shift is complete and range attained is not neutral.
* The transmission output speed is greater than 200 RPM for 1 second.

P0722 Condition 1
* DTC P0716, P0717, P0721, P0722, P0729, P0731, P0732, P0733, P0734, P0735, and P0736 is not set.
* The output speed is 600 RPM or greater for 1 second.
* The engine speed is greater than 200 RPM.
* A shift is not in progress.

P0722 Condition 2
* DTC P0716, P0717, P0721, P0722, P0729, P0731, P0732, P0733, P0734, P0735, and P0736 is not set.
* A shift is not in progress.
* The engine speed is greater than 200 RPM.
* The turbine speed is 1050 RPM or greater.
* Range attained is not neutral.
* The transmission fluid temperature is greater than -25°C (-13°F).

Conditions for Setting the DTC

P0721 Condition 1

The TCM detects an unrealistic change in output speed.

P0721 Condition 2

The TCM detects a noisy output speed signal.

P0722 Condition 1

The TCM detects an unrealistic change in output speed.

P0722 Condition 2

The TCM detects an output speed below 61 RPM when the transmission is in 3rd, 4th, 5th, or 6th gear for 1 second, or the turbine speed is greater than 1500 RPM for 1 second.

Diagnostic Aids

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

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Diagrams)
Connector End View Reference

* Component Connector End Views (Connector Views)
* Inline Harness Connector End Views (Diagrams)

Description and Operation

* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

J 38522 - Variable Signal Generator

Circuit/System Verification

1. Perform the Road Test (Initial Inspection and Diagnostic Overview) 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.
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.

Circuit/System Testing

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

1. Ignition OFF, remove the vehicle speed sensor connector.
2. Connect the J 38522 - signal generator to the vehicle speed sensor circuit, terminals A and B.
3. Adjust the J 38522 - signal 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 (Programming and Relearning) for TCM replacement, setup, and programming.

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

Component Testing

Static Testing

Note: You must perform the Circuit/System Testing first

1. Ignition OFF, remove the vehicle speed sensor. Refer to Speed Sensor Replacement (Service and Repair) 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 (Transmission Fluid Temperature Sensor) (Temperature Versus Resistance (Transmission Fluid Temperature Sensor))Temperature Versus Resistance (Speed Sensor) (Temperature Versus Resistance (Speed Sensor))Temperature Versus Resistance (Solenoid) (Temperature Versus Resistance (Solenoid)) for 2WD models or 1,420-2,140 ohms for 4WD models.

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

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Wiring Harness Replacement (Service and Repair)
* Speed Sensor Replacement (Service and Repair) , 2WD
* Vehicle Speed Sensor Replacement () , 4WD
* Control Module References (Programming and Relearning) for TCM replacement, setup, and programming

Repair Verification

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