B1027 The multiplex integrated control unit saw an out of range signal from the trunk key cylinder switch
What does B1027 mean on a Honda?
B1027. The multiplex integrated control unit saw an out of range signal from the trunk key cylinder switch. The trunk release may not respond to the key. This Honda-enhanced code applies to Honda and Acura models that use this code.
Common causes of B1027
- Faulty Trunk Key Cylinder Switch
- Trunk Key Cylinder Switch harness is open or shorted
- Trunk Key Cylinder Switch circuit poor electrical connection
- Faulty Multiplex Control Unit Module (MICU)
- Moisture or corrosion in the switch connector
How to fix B1027
- Confirm the code with a scan tool and test the trunk key cylinder switch in each position
- Inspect the trunk key cylinder switch connector and wiring for corrosion and loose pins
- Test the switch continuity and the signal circuit with a multimeter
- Repair any open or shorted wiring before replacing the switch
- Replace the trunk key cylinder switch if it fails testing, then clear codes and retest
Sources and review
- Last updated 2026-09-26.