Code Definition

U2004 — Audio Steering Wheel Control Unit is Not Responding

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

About U2004

U2004 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 U2004 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 is stored by the Audio Control Module when it stops receiving valid input from the steering wheel audio control switches over the control network, typically a LIN bus or low speed CAN. The steering wheel controls let the driver adjust volume, change tracks, answer calls, and trigger voice control, and their signals pass through the clock spring, also called the spiral cable, in the steering column on their way to the head unit. The code sets when those expected inputs or status messages are not received or acknowledged within a calibrated time. The driver may find the steering wheel a...

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