Code Definition

B1009 — Multiplex integrated control unit communication with combination switch control module lost

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

About B1009

B1009 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.

B1009 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 Honda Multiplex Integrated Control Unit (MICU) communicates with the Combination Switch Control Module (CSCM) over the vehicle's multiplex serial data network, receiving separate data messages for each stalk function. DTC B1009 is specifically set when the MICU loses the wiper switch message from the CSCM — this is distinct from B1007 which covers the headlight switch message from the same module. The CSCM transmits the wiper stalk position data (off, intermittent, low speed, high speed, mist, and washer) to the MICU, which then activates the corresponding wiper motor relay and washer pu...

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