Code Definition

B1040 — CAN Bus Communication Fault

System: Body  |  Type: Manufacturer-Specific  |  Make: Mercedes-Benz

About B1040

B1040 is a manufacturer-specific body diagnostic trouble code recorded for Mercedes-Benz vehicles. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1040 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

On Mercedes Benz vehicles, every networked control module continuously monitors the Controller Area Network (CAN) bus for valid message traffic and electrical integrity on the CAN High and CAN Low circuits. Fault code B1040 is stored when a module detects a loss of CAN communication because no valid frames are received within the expected timeout window, repeated frame errors are logged, or the transceiver enters a bus off state after too many consecutive transmit errors. The underlying cause is typically a physical layer fault such as a shorted or open bus wire, a damaged connector, or a fail...

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