P0502
DTC P0502
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provide an overview of each diagnostic category.
DTC Descriptor
DTC P0502
- Vehicle Speed Sensor (VSS) Absence of Signal
Diagnostic Fault Information
Circuit/System Description
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.
Conditions for Running the DTC
1. DTCs P0722 or P0723 are not active.
2. The ECM indicates the transmission output speed signal is valid.
Conditions for Setting the DTC
The difference between the two output speed signals is greater than 8 km/h (5 mph) for more than 1 second.
Action Taken When the DTC Sets
DTC P0502 is a Type A DTC.
Conditions for Clearing the DTC
DTC P0502 is a Type A DTC.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Diesel) (Electrical Diagrams)Automatic Transmission Controls Schematics (Gas) (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
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.
Circuit/System Testing
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.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Transmission Control Module Replacement (Service and Repair)
* Transmission Control Module Programming and Setup (Programming and Relearning)