U0139: Lost Communication With Suspension Control Module B

U0139 is a network communication code that indicates a loss of communication with Suspension Control Module B over the vehicle's CAN bus. On vehicles equipped with electronically controlled suspension, the suspension module communicates continuously with other modules to share ride height data, damper control commands, and sensor inputs. When the responsible module stops responding on the bus, U0139 is stored by whichever module first notices the silence. Suspension-related features controlled by that module may default to a fixed setting or be disabled entirely.

The fault is most often caused by a wiring issue on the CAN bus network near the suspension module, a corroded or damaged connector at the module itself, a blown fuse supplying the module, or an outright module failure. Because this is a communication fault rather than a sensor fault, it is worth checking the basics first: module supply voltage, ground integrity, and the connector condition. A CAN bus fault elsewhere on the network can also cause this code as a secondary effect, so checking for additional U-codes alongside U0139 will help establish whether this is an isolated module issue or a broader network problem.

The severity is logged as low, which suggests normal vehicle operation is largely unaffected, though any adaptive suspension features will not function correctly while the fault is present. Clear the code and road test to check if it returns. If it is persistent, a workshop with network diagnostics capability can trace the CAN bus and isolate the fault point without needing to guess at components.