WOMS
U code network Medium severity

U1646 Invalid or Missing Data for Vehicle Speed

The OBD2 code U1646 indicates that the vehicle's control module has detected invalid or missing data related to vehicle speed, which may affect the performance of various systems

Definition

The OBD2 code U1646 indicates that the vehicle's control module has detected invalid or missing data related to vehicle speed, which may affect the performance of various systems

Common causes

  • Faulty vehicle speed sensor
  • Damaged wiring or connectors
  • Faulty engine control module (ECM)
  • Faulty transmission control module (TCM)
  • Poor ground connections
  • Corroded or damaged connectors
  • Issues with the CAN bus communication
  • Malfunctioning ABS module
  • Incorrectly calibrated speedometer
  • Software issues or glitches in the vehicle's computer system

Common misdiagnoses

  • Faulty Vehicle Speed Sensor (VSS)
  • Malfunctioning Engine Control Module (ECM)
  • Wiring issues or shorts in the speed sensor circuit
  • Faulty ABS module
  • Incorrect tire size or calibration issues
  • Transmission problems
  • Issues with the instrument cluster
  • Faulty or corroded connectors in the speed sensor circuit

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide context and help identify the root cause of the issue

  2. 2. Inspect Vehicle Speed Sensor (VSS)

    Visual Inspection: Check the VSS for any physical damage, loose connections, or corrosion at the connector

  3. 3. Testing

    Use a multimeter to test the VSS for proper voltage and resistance according to the manufacturer's specifications. If the sensor is faulty, it may need to be replaced

  4. 4. Examine Wiring and Connectors

    Inspect the wiring harness and connectors related to the VSS and the modules communicating vehicle speed data. Look for frayed wires, broken connectors, or signs of wear

  5. 5. Ensure that all connections are secure and free of corrosion

  6. 6. Check the CAN Bus

    Use a scan tool to monitor the CAN bus for communication issues. If other modules are not communicating properly, it may indicate a problem with the bus itself

  7. 7. Look for any shorts or opens in the CAN wiring

  8. 8. Inspect the Instrument Cluster

    If the vehicle speed data is not being displayed correctly on the instrument cluster, there may be an issue with the cluster itself. Check for any faults or malfunctions in the cluster

  9. 9. Test the Engine Control Module (ECM)

    The ECM may be responsible for processing the vehicle speed data. If other troubleshooting steps do not resolve the issue, consider testing or reprogramming the ECM

  10. 10. Check for Software Updates

    Sometimes, manufacturers release software updates for the vehicle's modules. Check if there are any updates available that may address communication issues

  11. 11. Clear Codes and Test Drive

    After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code reappears

  12. 12. Consult Repair Manual

    Refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the VSS and communication protocols

  13. 13. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with OBD-II diagnostics and the specific vehicle make and model. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the U1646 code