CAN network

U0123 — Lost Communication with Yaw Rate Sensor Module

Severity: medium Drive with care, to a shop

What U0123 means

U0123 means other control modules are no longer receiving messages from the yaw rate sensor module over the CAN bus. This sensor measures how fast the body rotates around its vertical axis, which the stability control (ESC) uses to tell whether the car is starting to skid. Without that signal, ESC and related functions cannot work properly and shut down.

Symptoms

  • ESC or traction control warning light on
  • Other warning lamps, possibly including ABS
  • Stability and traction control unavailable
  • C0462 or other stability sensor codes may appear with it
  • Other modules on the same bus may act up

Possible causes

  1. Failed yaw rate sensor (often built into the airbag module or a standalone unit)
  2. Open, shorted or chafed CAN bus wiring
  3. Corroded connector or terminals
  4. Power supply or ground fault at the module
  5. Another faulty module loading down the bus
  6. Sensor not calibrated after replacement or battery disconnect

How to diagnose

  1. Run a full-module scan to see which modules are not communicating
  2. Review freeze frame data and note whether the fault is constant or intermittent
  3. Inspect the harness and connector at the yaw sensor module for water, corrosion, chafing or past repairs
  4. Check the module's power and ground against the wiring diagram
  5. Measure CAN bus voltages and resistance (typically about 60 ohms between CAN-H and CAN-L) at the diagnostic connector
  6. Unplug suspect modules one at a time only if the service procedure documents it
  7. Check battery voltage and terminal condition
  8. After repair, clear codes and perform any required sensor calibration

Common fixes

  • Repair wiring faults or corroded connectors
  • Restore the module's power or ground
  • Replace the yaw rate sensor or the module containing it, then calibrate it
  • Replace a faulty module that is disrupting the CAN bus
  • Perform ESC calibration and initialization after repair

Questions and answers

What does U0123 mean?

It means communication with the yaw rate sensor module was lost. Other modules cannot get its data over the CAN bus, so stability control cannot detect a skid.

Can I drive with U0123?

Yes, but carefully and not for long. The engine and brakes still work, but stability control is disabled, so the car is less protected from skids on wet or slippery roads.

Do I need to calibrate after replacing the sensor?

Usually yes. Many systems require a scan tool calibration or zero point reset, otherwise the code or ESC light may stay on.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.