AF40-6 (MDK) - Automatic Transmission

DTC P0502 or P0503

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0502
- Vehicle Speed Sensor (VSS) Circuit Low Voltage

DTC P0503
- Vehicle Speed Sensor (VSS) Circuit Intermittent

Circuit/System Description

The vehicle speed sensor (VSS) also called the output shaft speed (OSS) sensor creates a AC voltage signal that increases in frequency as vehicle speed increases. The transmission control module (TCM) receives and process this signal. The TCM provides a digital VSS signal on the data communication line to the ECM and other controllers connected to the data line.

Conditions for Running the DTC

P0502

* DTCs P0717 P0720 or P0722 are not active.

* The ECM indicates the transmission output speed signal is valid.

* The ignition voltage is 9-32 V.

* The engine speed is between 1 500-6 500 RPM.

P0503

* DTCs P0717 P0720 or P0722 are not active.

* The ECM indicates the transmission output speed signal is valid.

* The ignition voltage is 9-32 V.

* The engine speed is less than 150 RPM for 2 s.

* The engine speed is greater than 300 RPM for 2 s.

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 s.

Action Taken When the DTC Sets

DTCs P0502 and P0503 are Type B DTC.

Conditions for Clearing the DTC

DTCs P0502 and P0503 are Type B DTC.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics AF40-6 (MDK) - Automatic Transmission

Connector End View Reference

Component Connector End Views Sunshade - Left

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Description and Operation

Transmission Component and System Description Transmission Component and System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Verify DTC P0717 P0720 or P0722 is not set.

• If a DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

• If no DTC is set

2. Operate the vehicle at 16-32 km/h (10-20 MPH) while observing the scan tool Transmission OSS parameter.

3. Verify the Transmission OSS should vary with the vehicle speed and not drop out.

• If the OSS parameter does not change with the vehicle speed
Refer to Circuit/System Testing

• If the OSS parameter changes with the vehicle speed

4. Operate the vehicle within the Conditions for Running the DTC. It may be helpful to operate the vehicle within the conditions identified from the Freeze Frame/Failure Records data.

5. Verify the DTC do not set.

• If the DTC sets
Refer to Circuit/System Testing

• If the DTC does not set

6. All OK.

Circuit/System Testing

Note: Circuit/System Verification must be performed before proceeding with Circuit/System Testing.

1. Ignition OFF, and all vehicle systems OFF. Remove the K71 Transmission Control Module to disconnect the X2 harness connector. It may take up to 2 min for all vehicle systems to power down.

2. Test for infinite resistance between ground and the terminals listed below:

* Signal circuit terminal 19 at the X2 harness connector

* Signal circuit terminal 20 at the X2 harness connector

• If less than infinite resistance

1. Test for infinite resistance between the appropriate signal circuit and each terminal at the X2 harness connector.

• If less than infinite resistance, replace the wiring harness.

• If infinite resistance

2. Test for 95-100 ohms between terminal 19 and terminal 20 at the X2 harness connector.

• If not within 95-100 ohms , replace the automatic transmission assembly

• If infinite resistance

3. Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.

• If the DTC is set
Replace the K71 Transmission Control Module.

• If the DTC is not set

4. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Automatic transmission replacement, refer to Transmission Replacement Transmission Replacement.

* Wiring harness replacement, refer to Automatic Transmission Wiring Harness Replacement Service and Repair.

* Refer to Control Module References Control Module References for TCM replacement, programming and setup.

* Perform the Transmission Adaptive Functions Transmission Adaptive Functions.