What does it mean?
U1023 is a Network (CAN bus, module communications) fault code. It indicates: Invalid Data Received from Brake ECU .
Symptoms
- ABS and stability control warning lamps on, sometimes only after driving a short distance
- Traction and stability control cutting in when they should not, or not working at all
- Speedometer reading erratically or freezing
- Cruise control dropping out on its own
- Transmission shifting oddly on vehicles that use brake data for shift control
- Fault often appears only above a certain road speed
Likely causes
- Wheel speed sensor fault or a damaged reluctor ring, so the brake ECU broadcasts impossible speed values
- Brake ECU internal fault producing corrupted or out-of-range data
- Water and corrosion in a bus connector distorting the transmitted frames
- Chafed or partly broken bus conductor causing intermittent data corruption
- Yaw rate or steering angle sensor out of calibration, feeding bad values into the brake ECU's messages
- Mismatched tyre sizes or a temporary spare fitted, giving wheel speeds the system rejects
- Configuration or software mismatch after a component or module replacement
How to fix it
- Compare all four wheel speed values in live data at a steady speed and look for one that differs, drops out or reads zero
- Inspect the wheel speed sensors and reluctor rings for damage, debris and corrosion, and check the sensor air gaps
- Verify tyre sizes and condition on all four corners, and remove any temporary spare before retesting
- Check the steering angle and yaw rate sensor values against a straight, level standing position, and recalibrate if needed
- Inspect the bus wiring and connectors between the brake ECU and the gateway for corrosion and chafing
- Perform a wiggle test while monitoring live data to catch intermittent corruption
- Confirm the brake ECU configuration and software match the vehicle after any recent repair
- Replace the brake ECU only when sensors, wiring and configuration have all been proven correct