2ML70 - Automatic Transmission
DTC P0721-P0723
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
DTC P0723
- Output Speed Sensor Circuit Intermittent
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The Automatic Transmission Output Shaft Speed Sensor assembly has 2 internal hall-effect type sensors, and is capable of sensing both speed and direction. The Automatic Transmission Output Shaft Speed Sensor mounts to the A/T rear case assembly and is connected to the control solenoid valve assembly through a wire harness and connector. The sensor faces the hybrid direct, 2-3-4 clutch housing assembly machined teeth surface. The sensor receives 8.3-9.3 volts on the OSS supply voltage circuit from the transmission control module. As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft.
The two sensor elements in the Automatic Transmission Output Shaft Speed Sensor assembly are spaced approximately 1/2 a tooth apart.
* When the vehicle is moving in a forward direction, sensor A detects a particular tooth before sensor B.
* When the vehicle is moving in a reverse direction, sensor B detects a particular tooth before sensor A.
The electronics in the sensor combine the two signals and send a signal with a different pulse width. This signal is interpreted by the TCM for speed and direction and is transmitted through the data communication circuits to the engine control module (ECM) and the hybrid powertrain control module. The ECM, hybrid powertrain control module, and transmission control module compare the OSS signal with the ABS wheel speed sensor signal.
Conditions for Running the DTC
P0721
The ignition is ON.
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).
* Motor estimated Transmission Output speed is 150-5200 RPM
* Axle torque is 110-5000 NM.
P0723
The engine run time is greater than 6 seconds.
Conditions for Setting the DTC
P0721
The transmission control module detects an invalid Automatic Transmission Output Shaft Speed Sensor direction for 2.5 seconds.
P0722
* The transmission control module detects no signal from the Automatic Transmission Output Shaft Speed Sensor.
* The transmission output speed is less than 50 RPM for 1.5 seconds.
P0723
* The transmission control module detects an unrealistic signal drop from the Automatic Transmission Output Shaft Speed Sensor.
* Automatic Transmission Output Shaft Speed Sensor DTC P0723 has not failed this ignition.
* The transmission output speed is 1,000 RPM or greater for 6 seconds.
* The transmission output speed drops 1,000 RPM for greater than 6 seconds and does not recover.
Action Taken When the DTC Sets
P0721
The transmission control module calculates vehicle direction.
P0722 and P0723
The transmission control module calculates vehicle speed based on the wheel speed sensors.
Conditions for Clearing the DTC
* P0721 and P0723 are a Type A DTC.
* P0722 is a Type B DTC.
Diagnostic Aids
Inspect the Automatic Transmission Output Shaft Speed Sensor, harness, and connector pins for metallic debris and the hybrid direct, 2-3-4 clutch housing assembly machined teeth for damage or misalignment. Even one bent or misaligned tooth, and or contact with the Automatic Transmission Output Shaft Speed Sensor, may cause this DTC to set. Proper torque of 9-13 Nm (80-115 lb in) to the Automatic Transmission Output Shaft Speed Sensor mounting bolt is critical to proper Automatic Transmission Output Shaft Speed Sensor operation. The hybrid system is very sensitive to the Automatic Transmission Output Shaft Speed Sensor signal for overall operation.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (2ML70 - Automatic Transmission)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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 (Control Module References) for scan tool information.
Special Tools
J 38522 - Variable Signal Generator
For equivalent regional tools, refer to Special Tools (2ML70 - Automatic Transmission).
Circuit/System Verification
1. Operate the vehicle at 16-32 km/h (10-20 mph), observe the scan tool Transmission OSS parameter. The reading should be greater than 150 RPM and not drop out.
2. Observe the scan tool OSS Supply Voltage parameter. The reading should display OK.
Circuit/System Testing
1. Ignition ON, test for 8.3-9.3 V between the automatic transmission output shaft speed sensor ignition circuit terminal A and ground.
• If less than the specified range, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the Q8 control solenoid valve assembly.
• If greater than the specified range, test the ignition circuit for a short to voltage. If the circuit tests normal, replace the Q8 control solenoid valve assembly.
2. Ignition Off, connect the red lead of J 38522 - generator to the signal circuit terminal B and the black lead to the ignition circuit terminal A.
3. Adjust the J 38522 - generator to 8 V, the Frequency to 120 Hz and the Percent Duty Cycle to 50 percent.
4. Ignition ON, verify the scan tool Transmission OSS parameter is between 100-400 RPM.
• If not within the specified range, test the signal circuit for a short to voltage short to ground open/high resistance. If the circuit tests normal, replace Q8 control solenoid valve assembly.
5. If all circuits test normal, test or replace the B14A Automatic Transmission Output Shaft Speed Sensor.
Component Testing
Perform the Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test (Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Output Speed Sensor Replacement (2ML70 - Automatic Transmission) for Automatic Transmission Output Shaft Speed Sensor replacement
* Control Module References (Control Module References) for Control Solenoid Valve Assembly replacement, programming and setup.