P0722
DTC P0721 or P0722
Diagnostic Instructions
* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) 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.
Conditions for Running the DTC
P0721
* DTCs P0716, P0717, or P0722 are not active.
* A shift is complete and range attained is not neutral.
* The engine speed is between 200-7500 RPM.
P0722
* DTCs P0716, P0717, P0721, P0729, P0731, P0732, P0733, P0734, P0735, and P0736 are not active.
* The engine speed is between 200-7500 RPM.
Conditions for Setting the DTC
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.
Diagnostic Aids
You will have to drive the vehicle in order to experience a condition.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
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 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 (Road Test Procedure) .
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 - 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 (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 orVehicle Speed Sensor Replacement (Service and Repair) 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 orVehicle Speed Sensor Replacement (Service and Repair) for 4WD models.
2. Test for resistance between terminal A and terminal B of the turbine speed sensor. See Speed Sensor table, refer toTemperature 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 theDiagnostic 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 (Service and Repair) , 4WD
* Control Module References (Programming and Relearning) for TCM replacement, setup, and programming
Repair Verification
If another DTC is present, refer toDiagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) and perform the appropriate diagnostic procedure.