GM Service Manual Online
For 1990-2009 cars only

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 Descriptors

DTC P0722:  Output Speed Sensor (OSS) Circuit Low Voltage

DTC P0723:  Output Speed Sensor (OSS) Intermittent

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

OSS High Signal

P0722, P0723

P0722, P0723

P0722, P0723

P0722, P0723

OSS Supply Voltage

P0722, P0723

P0722, P0723

P0722, P0723

P0722, P0723

Typical Scan Tool Data

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Operating Conditions: Drive vehicle, normal operating temperature

Parameter Normal Range: 100-7,000 RPM

ISS/OSS Supply Voltage

Out of Range

Out of Range

Out of Range

Transmission OSS

0 RPM

0 RPM

0 RPM

Circuit/System Description

The automatic transmission (AT) output speed sensor (OSS) is a hall-effect type sensor. The OSS mounts to the control valve upper body assembly and connects to the control solenoid (w/body and TCM) valve assembly through a 2-wire harness and connector. The sensor faces the output shaft machined teeth surface. The sensor receives 8.3-9.3 volts on the input/output speed sensor (ISS/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, torque converter clutch (TCC) slip speed and gear ratio.

Conditions for Running the DTC

P0722

    • No OSS DTC P0723.
    • The ignition voltage is between 8.6 volts and 19.0 volts.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The selected range is not PARK or NEUTRAL.
    • The vehicle speed is greater than 5 km/h (3 mph).
    • The transmission input speed is between 1,000-6,500 RPM.
    • The engine speed is between 3,200-6,500 RPM.
    • The calc. throttle position is greater than 8 percent.
    • The engine torque is greater than 50 N·m (37 lb ft).
    • The TFT is greater than -40°C (-40°F).

P0723

    • No ISS DTCs P0716 or P0717.
    • No OSS DTC P0722.
    • The ignition voltage is between 8.6 volts and 19.0 volts.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • Greater than 5 seconds since last range change.
    • DTC P0723 has not passed this ignition cycle.

Conditions for Setting the DTC

P0722

The transmission output speed is 70 RPM or less for 4.5 seconds.

P0723

    • The transmission output speed does not change by more than 500 RPM for 2 seconds.
    • The transmission output speed is 360 RPM or greater for 2 seconds.
    • The transmission output speed drops 650 RPM for greater than 1.5 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 DIC/DTC

DTCs P0722 and P0723 are Type A DTCs.

Diagnostic Aids

    • DTC P0722 detects a very low vehicle speed signal when the vehicle has a large engine speed in a drive range, constant fault.
    • DTC P0723 detects a large unrealistic drop in the vehicle speed signal in a very short period of time, intermittent fault.
    • 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.
    •  Inspect the 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

Connector End View Reference

Component Connector End Views

Description and Operation

    •  Transmission General Description
    •  Transmission Component and System Description
    •  Electronic Component Description

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

Control Module References for scan tool information

Special Tools

    • DT-48616-10 Adapter Harness
    • J 38522 Variable Signal Generator

Circuit/System Verification

Operate the vehicle at 16-32 km/h (10-20 mph) while observing the transmission OSS on the scan tool. The transmission OSS should vary with the vehicle speed and not drop out.

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

    Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition OFF, remove the control valve body cover. Refer to Control Valve Body Cover Removal in Control Valve Body Assembly Removal .
  2. Connect the DT-48616-10 .
  3. Disconnect the OSS from the control solenoid (w/body and TCM) valve assembly.
  4. Connect the J 38522 between the high and low signal terminals of the control solenoid (w/body and TCM) valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Input Shaft Speed/Output Shaft Speed Input Test for further instructions.
  5. Set the J 38522 Signal to 8 volts, the Frequency to 120 and the Percent Duty Cycle to 50.
  6. Ignition ON, observe the scan tool Transmission OSS parameter. The scan tool Transmission OSS parameter should be between 100-400 RPM.
  7. If the Transmission OSS parameter is between 100-400 RPM, replace the ISS/OSS assembly.
    If no OSS RPM is displayed or the parameter is out of range, replace the control solenoid (w/body and TCM) valve assembly.
  8. Inspect the 3-5-R clutch piston housing machined teeth surface for damage or misalignment.
  9. If a condition is found, repair or replace as necessary.
  10. If all circuits test normal, test or replace the output speed sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

       Important: Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

    • Refer to Control Module References for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming.
    • Perform the Service Fast Learn Adapts following all transmission related repairs.
    • Perform the Input and Output Speed Sensor Removal and the Input and Output Speed Sensor Installation .
    • Perform the Control Solenoid Valve and Transmission Control Module Assembly Input Shaft Speed/Output Shaft Speed Input Test .