U0123 — Lost communication with the yaw rate sensor module

Diagnostic algorithm

1. Connect a diagnostic scanner capable of reading all modules and live CAN traffic. Record U0123 occurrence count and freeze frame data.
2. Check for additional network codes. If multiple modules on same bus report comms faults, suspect shared CAN power/ground or wiring.
3. Visually inspect yaw rate sensor, connectors, and local harness for damage, corrosion or contamination. Repair any obvious issues.
4. Verify sensor power and ground at the connector with key ON. Check fuses and relays feeding the sensor circuit. Repair faults.
5. With ignition ON, measure CANH and CANL voltages at the yaw sensor connector. Confirm recessive voltages ≈2.5 V and correct dominant swings with an oscilloscope if possible.
6. With ignition OFF, measure resistance between CANH and CANL to confirm ~60 Ω termination. If out of range, inspect termination resistors and wiring for opens/shorts.
7. Perform continuity and short-to-ground/battery tests on CANH/CANL to local chassis and battery. Isolate harness sections to find intermittent shorts.
8. If wiring checks good, disconnect the yaw sensor module and attempt communication with module on the network (if possible) or substitute a known-good module to confirm module failure.
9. If a module replacement is done, follow manufacturer procedures for coding/configuration and software updates. Clear codes and perform a test drive while monitoring live data.
10. If intermittent failure remains, use an oscilloscope to capture CAN frames while performing wiggle tests on the harness to locate intermittent connector or wire faults.