U01xx fault codes: Lost communication

One control unit no longer hears another on the network: engine, gearbox, ABS, airbags, dashboard. The cause is often electrical — supply, ground, connector — rather than the silent unit itself.

How to read this code

The letter U names the system: Network. The next digit, 1, locates the fault: lost communication.

These codes are generic: they mean the same thing on every make. Some manufacturer tools display them with a two-digit suffix, such as P0101-00 or P010100: the suffix refines the fault type, and the base code keeps its meaning.

The codes of this family, part by part

Communication between control units

• U0100Lost Communication With ECM/PCM A
• U0101Lost Communication With TCM
• U0102Lost Communication With Transfer Case Control Module
• U0121Lost Communication With Anti-Lock Brake System (ABS) Control Module
• U0122Lost Communication With Vehicle Dynamics Control Module
• U0126Lost Communication With Steering Angle Sensor Module
• U0131Lost Communication With Power Steering Control Module
• U0140Lost Communication With Body Control Module
• U0151Lost Communication With Restraints Control Module
• U0155Lost Communication With Instrument Panel Cluster (IPC) Control Module
• U0164Lost Communication With HVAC Control Module
• U0184Lost Communication With Radio