Honda Civic Service Manual: Battery System

Electrical

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Battery Removal and Installation

Removal 1. Battery Terminal - Disconnection 1. Make sure the ignition switch is in LOCK (0). ...

See also:

Honda Civic Service Manual. Multiplex Integrated Control System (MICS) Description - Functional Control ('13: except Natural Gas models)
Power Supply Voltage Monitoring Function The MICU monitors the power supply voltage (backup voltage). If the voltage drops below 10 V, the MICU does not store DTCs. Input Output MICU Battery voltage ...