U0125

U0125 is a diagnostic trouble code used in OBD-II vehicle diagnostics to indicate lost communication with the Anti-lock Brake System (ABS) Control Module. It belongs to the U family, which covers network or communication issues rather than direct sensor readings. A U0125 means one or more control modules on the vehicle’s CAN (Controller Area Network) bus failed to exchange data with the ABS module within the expected time frame, potentially affecting braking system monitoring and control.

Symptoms commonly associated with U0125 include the ABS warning light illuminating on the dashboard, intermittent or reduced ABS function, and sometimes interactions with other networked systems such as the traction control or stability control. The presence of other CAN-related codes may accompany U0125, and vehicle behavior can vary by make and model.

Common causes include damaged or corroded wiring or connectors between the ABS module and other controllers, a blown fuse or poor power/ground to the ABS module, a faulty ABS control module or other ECUs on the CAN bus, and software or calibration mismatches between modules. Environmental factors like moisture, vibration, or loose connections can also trigger intermittent communication faults.

Diagnosis and repair generally start with a comprehensive scan to confirm U0125 and identify any related codes. Inspect the ABS harness and connectors for damage, corrosion, and secure fit. Check power and ground to the ABS module, fuses, and battery condition. Verify CAN bus continuity, absence of shorts, and proper termination. Update or reflash software if recommended by the manufacturer, and replace the ABS module or harness as needed. After repair, clear codes and perform a road test to confirm resolution.