Chevrolet Trax: DTC P0502 OR P0503: Vehicle speed sensor (VSS)

DIAGNOSTIC CODE INDEX

DTC P0502 OR P0503: VEHICLE SPEED SENSOR (VSS)

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 P0502

Vehicle Speed Sensor (VSS) Circuit Low Voltage

DTC P0503

Vehicle Speed Sensor (VSS) Circuit Intermittent

Diagnostic Fault Information

Typical Scan Tool Data

Vehicle Speed Sensor

Circuit/System Description

The vehicle speed sensor (VSS) is a 3 wire sensor. The engine control module (ECM) provides a 5 volt reference circuit, low reference circuit and a signal circuit to the VSS. The VSS is a Hall Effect type sensor that produces a square wave output signal to the ECM. As vehicle speed increases, the output frequency of the VSS signal increases. The ECM converts the square wave output signal into vehicle speed shown as km/h (MPH).

The ECM supplies the VSS signal to other control modules on the vehicle through the serial data communications line.

Conditions for Running the DTC

P0502

• DTC P0503 is not set.
• Ignition voltage is between 9-16 V.
• Throttle position is 15% or greater.
• Engine speed is between 1,500-6,500 RPM.

P0503

• Ignition voltage is between 9-16 V.
• Engine speed is between 200-7,500 RPM for 5 s or greater.
• Transmission Output Shaft Speed signal is 200 RPM or greater for 2 s or greater.

Conditions for Setting the DTC

P0502

Transmission Output Shaft Speed signal is less than 60 RPM for 4.5 s.

P0503

Change in Transmission Output Shaft Speed signal is 350 RPM or greater for 3.3 s.

Action Taken When the DTC Sets

P0502 and P0503 are Type B DTCs.

Conditions for Clearing the DTC

P0502 and P0503 are Type B DTCs.

Diagnostic Aids

The battery must be fully charged. Refer to Battery Inspection/Test .

Reference Information

Schematic Reference

Manual Transmission Schematics (Encore, MR5), Manual Transmission Schematics (Trax, MR5)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

Description and Operation

Transmission System Description and Operation

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 (LUV) , Powertrain Diagnostic Trouble Code (DTC) Type Definitions (2H0)

Scan Tool Reference

K20 Engine Control Module: Scan Tool Information (LUV or 2H0)

Special Tools

J-38522-A Vehicle Signal Generator

For equivalent regional tools, refer to Special Tools.

Circuit/System Verification

CAUTION: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel.

1. Raise and support the drive wheels in a horizontal position.
2. Start and idle the engine.
3. Place the transmission in second gear and release the clutch pedal.
4. Verify the scan tool Vehicle Speed Sensor parameter increases as the drive wheel speed increases.

• If the Vehicle Speed Sensor parameter does not increase

Refer to Circuit/System Testing

• If the Vehicle Speed Sensor parameter does increase

5. Operate the vehicle within the conditions for running the DTC to verify the DTC does not set. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

If the DTC sets

Refer to Circuit/System Testing.

If the DTC does not set

6. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connector at the B115 Vehicle Speed Sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the low reference circuit terminal 2 and ground.

If 10 ohms or greater

1. Disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for less than 2 ohms in the circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.

If less than 10 ohms

3. Ignition ON.
4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.

If less than 4.8 V

1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Test for less than 2 ohms in the 5 V reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.

If greater than 5.2 V

1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module, Ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.

If between 4.8-5.2 V

5. Ignition OFF, connect the test leads of the J-38522-A vehicle signal generator as follows:

• Red test lead to the signal circuit terminal 3 at the B115 Vehicle Speed Sensor wire harness connector.
• Black test lead to ground at the transmission case.
• Double black power and ground lead wire to B+ and ground.

6. Set and adjust the J-38522-A vehicle signal generator to the following switch positions:

• Signal switch to 5 V.
• Frequency switch to 600 Hz.
• Duty cycle switch to 50% or normal position.

7. Ignition ON.
8. Verify the scan tool Vehicle Speed Sensor parameter displays between 41-51 km/h (25-31 mph).

• If the vehicle speed sensor parameter is not within the specified range

1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit terminal 3 and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Test for less than 2 ohms in the signal circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.

If the vehicle speed sensor parameter is within the specified range

9. Replace the B115 Vehicle Speed Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Control Module References for ECM replacement, programming and setup.

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