P0721
DTC P0721-P0723
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P0721
- Output Speed Sensor Performance
DTC P0722
- Output Speed Sensor (OSS) Circuit Low Voltage
DTC P0723
- Output Speed Sensor (OSS) Intermittent
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The output speed sensor (OSS) is a directional hall-effect type sensor. The OSS mounts to the output module and connects to the control solenoid (w/body and TCM) valve assembly through a wire harness and connector. The sensor faces the output shaft machined teeth surface. The sensor receives 8.3-9.3 volts on the OSS supply voltage circuit from the transmission control module (TCM). As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft. This signal is transmitted through the OSS signal circuit to the TCM. The TCM uses the OSS signal to determine line pressure, transmission shift patterns, and gear ratio.
Conditions for Running the DTC
DTC P0721 or P0722
* No OSS DTCs P0721 or P0723.
* The selected range is not PARK or NEUTRAL.
* The vehicle speed is greater than 16 km/h (10 mph).
* The transmission input speed is between 1,500-5,000 RPM.
* The engine speed is between 3,000-5,000 RPM.
* The calculated throttle position is greater than 8 percent.
DTC P0723
* No OSS DTCs P0721 or P0722.
* The engine run time is greater than 5 seconds.
* The time since the last range change is greater than 6 seconds.
Conditions for Setting the DTC
DTC P0721 or P0722
* The TCM detects no signal from the OSS.
* The transmission output speed is less than 200 RPM for 5 seconds.
DTC P0723
* The TCM detects an unrealistic signal drop from the OSS.
* OSS DTC P0723 has not failed this ignition.
* The transmission output speed is 1,000 RPM or greater for 2 seconds.
* The transmission output speed drops 1,300 RPM for greater than 4 seconds and does not recover.
Action Taken When the DTC Sets
* The TCM freezes transmission adaptive functions.
* The TCM turns OFF all solenoids.
Conditions for Clearing the DTC
DTCs P0721, P0722, and P0723 are Type A DTCs.
Diagnostic Aids
Inspect the OSS, harness, connector and control solenoid (w/body and TCM) valve assembly pins for metallic debris and output shaft machined face for damage or misalignment. Proper torque of the OSS mounting bolt is critical to proper OSS operation. Use a terminal test kit for any test that requires probing the control solenoid (w/body and TCM) valve assembly harness connector or a component harness connector.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views
Electrical Information Reference
* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs
* High Voltage Disabling
* High Voltage Enabling
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
* Scan Tool Output Controls (Scan Tool Output Controls)
* Scan Tool Data List (Scan Tool Data List)
* Scan Tool Data Definitions (Scan Tool Data Definitions)
Special Tools
J 38522 Variable Signal Generator
Circuit/System Verification
Operate the vehicle at 16-32 km/h (10-20 mph) while observing the Transmission OSS and OSS Supply Voltage parameters on the scan tool.
The Transmission OSS should vary with the vehicle speed and not drop out.
The OSS Supply Voltage should display OK.
If the OSS Supply Voltage displays out of range, the OSS, OSS supply voltage circuit, or the control solenoid (w/body and TCM) valve assembly is shorted.
Circuit/System Testing
1. Disconnect the OSS connector.
2. Test for 8.3-9.3 volts between the OSS supply voltage circuit and ground.
• If less than 8.3 volts, test the OSS supply voltage circuit for an open/high resistance or short to ground.
• If the OSS supply voltage circuit tests normal, replace the control solenoid (w/body and TCM) valve assembly.
• If greater than 9.3 volts, test the OSS supply voltage circuit for a short to voltage.
3. Using a terminal test kit, connect the J 38522 to the OSS signal circuit.
4. Set the J 38522 Signal to 5 volts, the Frequency to 120 and the Percent Duty Cycle to 50.
5. With the ignition ON, observe the OSS Signal parameter, The OSS Signal parameter should display between 100-400 RPM.
• If the OSS signal is not within the specified range, test the OSS signal circuit for an open/high resistance, short to ground, or a short to voltage.
• If the circuit tests normal, replace the control solenoid (w/body and TCM) valve assembly.
• If the OSS signal is within the specified range, visually inspect the OSS and the output shaft machined surface for damage or misalignment. If OK, replace the OSS.
Component Testing
Perform the Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test (Control Solenoid Valve and TCM Assembly Solenoid Performance Test) .
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
1. Perform the Output Speed Sensor Replacement (M99 - Automatic Transmission) .
2. Control solenoid (w/body and TCM) valve assembly replacement. Refer to Control Module References for replacement, setup, and programming.
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and TCM Assembly Solenoid Performance Test) .
4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test (Control Solenoid Valve and TCM Assembly Solenoid Performance Test) .