Code Definition

U2500 — (CAN) Lack of Acknowledgement From Engine Management

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

About U2500

U2500 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 U2500 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

This DTC sets when a control module attempts to communicate with the engine management system, typically the ECM or PCM, over the CAN network and does not receive the expected acknowledgement to its messages. On CAN, a transmitting module expects an acknowledgement bit from the receiving modules, and a persistent lack of acknowledgement from engine management indicates the ECM is not responding on the bus. This usually means the engine management module has dropped off the network through a power, ground, or wiring fault, or that the CAN circuit to it is broken. Because so many systems depend ...

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