U1646 – Invalid or Missing Data for Vehicle Speed.
The ODBII 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.
The severity of ODBII code U1646 is moderate.
Common Causes For: U1644 Lost Communication with Body Control Module (BCM).
- 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 misdiagnosis for U1646 Invalid or Missing Data for Vehicle Speed.
- 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
Common Troubleshooting Steps
The OBD-II code U1646 indicates an “Invalid or Missing Data for Vehicle Speed.” This code typically points to a communication issue between the vehicle’s modules, particularly related to the vehicle speed sensor (VSS) or the data being transmitted over the CAN (Controller Area Network) bus. Here are some common troubleshooting steps to diagnose and resolve this issue:
- 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.
- Inspect Vehicle Speed Sensor (VSS): **Visual Inspection: Check the VSS for any physical damage, loose connections, or corrosion at the connector.
- **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.
- 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.
- Ensure that all connections are secure and free of corrosion.
- 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.
- Look for any shorts or opens in the CAN wiring.
- 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.
- 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.
- 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.
- 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.
- Consult Repair Manual: Refer to the vehicle’s service manual for specific diagnostic procedures and specifications related to the VSS and communication protocols.
- 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.