For 1990-2009 cars

### 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 P0722: Output Speed Sensor Circuit Low Voltage
DTC P0723: Output Speed Sensor Circuit Intermittent

### Circuit/System Description

The vehicle speed sensor (VSS), also called the output shaft speed sensor (OSS) provides vehicle speed information to the transmission control module (TCM). The VSS is a permanent magnet generator. The sensor is mounted in the transmission case facing the rear internal gear which is splined to the output shaft assembly. As the output shaft and internal gear rotate, the toothed rotor of the internal gear produces AC voltage as the rotor teeth pass through the magnetic field of the sensor. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The TCM converts the voltage to vehicle speed. The TCM uses the output shaft speed signal to determine shift timing and torque converter clutch (TCC) scheduling.

### Conditions for Running the DTC

#### P0722

• | No input speed sensor (ISS) DTCs P0716, P0717.

• | No OSS DTCs P0722 or P0723.

• | No transmission fluid pressure (TFP) DTCs P1810, P1815, P1816, P1818.

• | The transmission is not in PARK or NEUTRAL.

• | Transmission fluid temperature (TFT) is between -40 to +150°C (-40 to +302°F).

• | The throttle position is 8 percent or greater.

• | The engine torque is greater than 50 N·m (37 lb ft).

• | The input speed is greater than 1,500 RPM.

• | The TCC slip speed is at least -20 RPM.

#### P0723

• | No 1-2 Shift Solenoid Electrical DTC P0974.

• | No ISS DTCs P0716 or P0717.

• | The transmission is not in PARK or NEUTRAL.

• | The transmission output speed is greater than 1,400 RPM for 2 seconds or greater.

• | One of the following conditions exist:

- | The transmission input shaft speed has changed less than 500 RPM for at least 2 seconds.

- | The transmission output shaft speed has not increased at least 500 RPM for at least 2 seconds.

### Conditions for Setting the DTC

#### P0722

The transmission output shaft speed is 50 RPM or less for 4.5 seconds.

#### P0723

The transmission output shaft speed drops 1,200 RPM or greater for at least 3.25 seconds.

### Action Taken When the DTC Sets

• | DTC P0722 and P0723 are Type B DTCs.

• | The TCM commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

• | The TCM calculates vehicle speed from the automatic transmission input shaft speed sensor and commanded gear.

### Conditions for Clearing the DTC

DTCs P0722 and P0723 are Type B DTCs.

### Diagnostic Aids

• | Inspect the rear internal gear teeth for damage.

• | Visually inspect the OSS for cracks or damage.

• | Ensure the OSS is properly torqued to the transmission housing.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Transmission General Information

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Transmission Control Module Scan Tool Information

#### Special Tools

J 35616 GM-Approved Terminal Test Kit

### Circuit/System Verification

1. Raise and support the drive wheels.
2. Start and idle the engine.
3. Place the transmission in DRIVE.
4. Monitor Transmission OSS on the scan tool.
5. The Transmission OSS on the scan tool should be greater than 100 RPM.

### Circuit/System Testing

1. Measure the resistance between the OSS high signal circuit and the OSS low signal circuit. The resistance should be between 1,377-3,355 ohms (2WD) or 1,420-2,140 ohms (AWD/4WD).

⇒ | If the value is greater than 3,355 ohms (2WD) or 2,140 ohms (AWD/4WD), test the OSS high signal circuit and the OSS low signal circuit for an open.

⇒ | If the value is less than 1,377 ohms (2WD) or 1,420 ohms (AWD/4WD), test the OSS high signal and the OSS low signal circuits for a shorted together condition.

2. Measure the resistance of the OSS high signal circuit to ground. The resistance should be greater than 10M ohms.

⇒ | If the value is less than 10M ohms, repair the short to ground.

3. Measure the resistance between the OSS low signal circuit and ground. The resistance should be greater than 10M ohms.

⇒ | If the value is less than 10M ohms, repair the short to ground.

4. Reconnect the TCM connector. Disconnect the OSS connector. Ignition ON, test the ISS high signal circuit for a short to voltage.

⇒ | If all circuits/connections test normal, test or replace the OSS.

### Component Testing

Verify the OSS resistance is within the specified range.

⇒ | Refer to Component Resistance .

Using the J 35616 GM-approved terminal test kit, connect the DMM between the OSS high signal and the OSS low signal circuits at the OSS connector. Raise and support the drive wheels. While rotating the drive wheels by hand ensure the AC voltage reading on the DMM is above 0.4 volts.

⇒ | If the AC voltage is not above 0.4 volts, replace the OSS.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• | Ensure that the OSS is 500 RPM or greater for 3 seconds and does not change more than 500 RPM or greater for 3 seconds.

• | Vehicle Speed Sensor Replacement

• | Control Module References for TCM replacement, setup and programming