Diagnostic Instructions
DTC Descriptors
DTC P0722: Output Speed Sensor (OSS/VSS) Circuit Low Voltage
DTC P0723: Output Speed Sensor (OSS/VSS) Circuit Intermittent
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
OSS/VSS High Signal
| P0722, P0723
| P0722, P0723
| P0722, P0723
| P0722, P0723
|
OSS/VSS Low Signal
| --
| P0722, P0723
| --
| P0722, P0723
|
Typical Scan Tool Data
Transmission Output Speed Sensor
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
|
Operating Conditions:
Drive vehicle, normal operating temperature
Parameter Normal Range:
100-7,000 RPM
|
Transmission OSS/VSS
| 0 RPM
| 0 RPM
| 0 RPM
|
Circuit/System Description
The automatic transmission (AT) OSS/VSS system is a 2-wire pulse generator consisting of a speed sensor assembly, located in the case extension, and a toothed output speed sensor (OSS/VSS) reluctor wheel, which is pressed onto the final
drive carrier assembly. As the vehicle drives forward, the OSS/VSS reluctor wheel rotates. This rotation produces a variable AC signal in the pick-up coil that is proportional to vehicle speed. The transmission control module (TCM) uses this signal
in order to calculate vehicle speed, shift timing, torque converter clutch (TCC) slip speed, and gear ratios.
Conditions for Running the DTC
P0722
| • | No ISS DTC P0716 or P0717. |
| • | No TPS DTC P0120, P0121, P0122, P0123, P0220, P0221, P0222, P0223, P0225, P0226, P0227, P0228, P1120, P1121, P1122, P1125, P1280, P1281, P1282, P1283, P1285, P1286, P1287 or P1288. |
| • | Ignition voltage is 8.0-18.0 V. |
| • | The transmission is not in PARK or NEUTRAL. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
| • | The calc. throttle position is 8 percent or greater. |
| • | The input shaft speed is greater than 1,500 RPM. |
| • | The torque converter clutch (TCC) slip speed is -20 RPM or greater. |
| • | The transmission fluid temperature (TFT) is -40°C (-40°F) or greater. |
P0723
| • | No ISS DTC P0716 or P0717. |
| • | No 1-2 SS electrical DTC P0974. |
| • | Ignition voltage is 8.0-18.0 V. |
| • | The transmission is not in PARK or NEUTRAL. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
| • | The time since the last gear selector range change is 6 seconds or greater. |
| • | The output speed is 350 RPM or greater for 2 seconds. |
| • | The transmission OSS/VSS changes less than 175 RPM for 2 seconds. |
| • | The ISS changes 500 RPM or less for 2 seconds. |
Conditions for Setting the DTC
P0722
The output shaft speed is 50 RPM or less for 4.5 seconds.
P0723
The output shaft speed drops greater than 420 RPM for 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 based on engine speed and gear ratio. |
Conditions for Clearing the DTC
DTC P0722 and P0723 are type B 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/VSS, harness, connector, and TCM 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/VSS mounting bolt is critical to proper OSS/VSS operation. |
| • | Use a terminal test kit for any test that requires probing the TCM harness connector, the 20-way connector, or a component harness connector. |
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Description and Operation Reference
Transmission General Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
| • | J 38522
Variable Signal Generator |
| • | J 44257
Main Wiring Harness Connector Remover |
Circuit/System Verification
- Operate the vehicle at 16-32 km/h (10-20 mph) while observing the transmission OSS/VSS on the scan tool. The transmission OSS/VSS RPM and OSS/VSS AC voltage 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.
- Ignition OFF. Disconnect the X1 harness connector at the TCM.
Important: When test probing TCM harness terminals, it is imperative to use the proper test probe from the most current version of the J 35616 GM terminal test kit. Use of the brown J 35616-6 (1.00 mm) PCM probe in a 0.64 mm
terminal will deform the terminal, resulting in intermittent open conditions. The correct probe for TCM harnesses is the light blue J 35616-64B probe.
- Using the light blue probes J 35616-64B test for greater than 250 Ω from the OSS/VSS high signal circuit terminal 41 X1 TCM and the OSS/VSS low signal circuit terminal 16 X1 TCM to a good ground.
| ⇒ | If less than the specified value, test the affected circuit for a short to ground. If both circuits test normal, replace the OSS/VSS. |
- Disconnect the X1 connector at the OSS/VSS.
- Using a 5A fused jumper wire and the light blue probes J 35616-64B, test for greater than 10K Ω between the OSS/VSS high signal circuit terminal 41 X1 TCM and all other circuits of the X1 TCM harness.
| ⇒ | If less than the specified value, the affected circuits are shorted together. |
- Using a 5A fused jumper wire and the light blue probes J 35616-64B, test for greater than 10K Ω between the OSS/VSS low signal circuit terminal 16 X1 TCM and all other circuits of X1 TCM harness.
| ⇒ | If less than the specified value, the affected circuits are shorted together. |
- Using the light blue probes J 35616-64B and the grey probes J 35616-2A, test the OSS/VSS high signal circuit for less than 10 Ω between terminal 41 X1 TCM harness and terminal B X1 OSS/VSS.
| ⇒ | If greater than the specified value, repair the open or high resistance in the affected circuit. |
- Using the light blue probes J 35616-64B and the grey probes J 35616-2A, test the OSS/VSS low signal circuit for less than 10 Ω between terminal 16 X1 TCM harness and terminal A X1 OSS/VSS.
| ⇒ | If greater than the specified value, repair the open or high resistance in the affected circuit. |
- Using the grey test probes J 35616-2A test for 1,650-3,180 Ω between the OSS/VSS high signal circuit, OSS/VSS pin B and the OSS/VSS low signal circuit, OSS/VSS pin A.
| ⇒ | If not within the specified range, replace the OSS/VSS. |
- If all circuits and connections test normal, replace the TCM.
Component Testing
- Verify the OSS/VSS resistance is 1,650-3,180 Ω.
| ⇒ | If the resistance is not within the specified range, replace the OSS/VSS. |
- Using the GM terminal test kit, connect the DMM between the OSS/VSS high signal, OSS/VSS connector pin B, and the OSS/VSS low signal circuits, OSS/VSS connector pin A, at the OSS/VSS connector. Raise and support the drive wheels. While
rotating the drive wheels by hand, ensure the AC voltage reading on the DMM is greater than 0.4 V.
| ⇒ | If the AC voltage is not greater than 0.4 V, replace the OSS/VSS. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
