The vehicle speed sensor (VSS) also called the output speed sensor (OSS) creates a AC voltage signal that increases in frequency as vehicle speed increases. The transmission control module (TCM) receives and processes this signal. The TCM provides a digital VSS signal on the data communication line to the engine control module (ECM) and other controllers connected to the data line. The TCM also provides an identical VSS signal on a separate circuit to the ECM. The ECM will test and compare the two signals for being identical and valid.

1. DTCs P0722 or P0723 are not active.
2. The ECM indicates the transmission output speed signal is valid.

The difference between the two output speed signals is greater than 8 km/h (5 mph) for more than 1 second.

DTC P0502 is a Type A DTC.

DTC P0502 is a Type A DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. If DTCs P0722 or P0723 are set, diagnose those DTCs first.
2. Observe the TCM output speed signal parameters and the ECM speed signal parameters with a scan tool, while driving the vehicle. Both parameter values should be identical.
3. 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.

1. Ignition OFF, disconnect the TCM harness connector.
2. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 5 and ground.

⇒	If less than the specified range, test the 5 volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the ECM.

⇒	If greater than the specified range, test the 5 volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

3. If all the circuits test normal, replace the TCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.