Code Definition

B1178 — F-CAN Communication Line Signal Error

System: Body  |  Type: Manufacturer-Specific  |  Make: Honda

About B1178

B1178 is a manufacturer-specific body diagnostic trouble code recorded for Honda 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.

B1178 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

The Gauge Control Module (GCM) monitors the integrity of the F CAN communication lines on Honda vehicles, which carry high speed data between major control modules such as the PCM, ABS/VSA, MICU, SRS and gauge cluster. DTC B1178 is set when the GCM detects abnormal voltage levels, corrupted message frames, missing acknowledgements, or invalid bit timing on the F CAN bus for a defined period. The F CAN network uses a twisted pair of wires (CAN High and CAN Low) with 120 ohm termination at each end of the backbone, and modules expect differential voltage swings of approximately 2V peak during ac...

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