Code Definition

U0203 (87) — Lost Communication With Door Control Module E

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

About U0203

U0203 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 U0203 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 vehicle control modules exchange operational data over the Controller Area Network (CAN) bus. DTC U0203 sets when one or more modules fail to receive valid CAN messages from Door Control Module E within a calibrated time window. A failure type byte such as 87 reported with the code indicates a missing or invalid message rather than a signal quality problem. This condition occurs when Door Control Module E is offline due to loss of power or ground, a CAN circuit fault, or an internal module failure. The door assigned to Module E varies by manufacturer and body style, commonly a sliding or r...

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