Code Definition

U0129 (00-2F) — Missing Communication with Brake Control Module A

System: Network Communication  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About U0129

U0129 is a generic (obd-ii standard) network communication diagnostic trouble code. It belongs to the U-prefix family of codes, which covers inter-module network communication (CAN, LIN, FlexRay, or similar) faults.

Scanning & clearing: Network (U) codes report communication faults between modules. When diagnosing U-codes, checking the vehicle's CAN bus integrity, supply/ground at each module, and reading all modules for related faults is usually the first step.

Because U0129 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Powertrain Control Module (PCM) and other vehicle control modules exchange braking, wheel speed, ABS event, and stability control information with Brake Control Module A over the Controller Area Network (CAN) bus. The brake control module is a safety critical node, so a loss of its CAN messages causes companion modules to set lost communication codes and disable functions that depend on brake data. DTC U0129 (sub codes 00 to 2F) is set when a control module detects that expected CAN messages from Brake Control Module A are not received within the calibrated time limit, indicating a complet...

Join TaT to view the complete code information and diagnostic details.

Quick Facts