Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
MICU Control Functions Index
The MICU (built into the under-dash fuse/relay box) is one of the B-CAN components. The MICU controls many systems related to the body controller area network, and also works as a gateway to diagnose the other B-CAN circuits with the HDS.
Refer to each system circuit diagram for details.
| System | Function |
|---|---|
| Multiplex Control | Sends the switch input/output signal information to the MICU. The MICU controls the ECUs electric load and communication based upon the information received via the B-CAN. |
| On-Board Diagnosis | The MICU has a gateway function which sends the results of the MICU internal diagnosis and the B-CAN connected ECUs diagnosis to the HDS. |
| Self-Diagnosis | Test mode 1 diagnoses the communication line between the MICU and B-CAN connected unit. Test mode 2 checks the switch inputs connected to the MICU. |
| Interior Light(s) | The MICU controls the interior lights ON, OFF and dimming based upon the information of the related switches and/or the B-CAN related information. |
| Sleep Function | The MICU has a sleep function, which it enters during the power down mode. |
The MICU also controls the function of these circuits:
- Entry lights (map lights and ceiling light)
- Exterior lights (including the daytime running lights)
- Horn
- Interlock system
- Key-in reminder
- Keyless entry
- Lights-on reminder
- Power door locks
- Power window key-off timer
- Seat belt reminder
- Security alarm
- Turn signal/hazard warning lights
- Wiper/washer
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.