2011 Honda Odyssey Owner's Manual - Page 666

If the Engine Won't Start Turn the ignition switch to the ON (II) position. Turn on the headlights, and check their brightness. If the headlights are very dim or do not come on at all, the battery is discharged. See Jump Starting on page 665 . If you see a ''CHECK BATTERY SENSOR'' message on the multiinformation display (or ''CHECK BATT SENSOR'' message on the information display on some models) when you try to start the engine, the battery is discharged. If it will not start, see Jump Starting on page 665 . Turn the ignition switch to the START (III) position. If the headlights do not dim, check the condition of the fuses. If the fuses are OK, there is probably something wrong with the electrical circuit for the ignition switch or starter motor. You will need a qualified technician to determine the problem. See Emergency Towing on page 683 . If the headlights dim noticeably or go out when you try to start the engine, either the battery is discharged or the connections are corroded. Check the condition of the battery and terminal connections (see page 649 ). You can then try jump starting the vehicle from a booster battery (see page 665 ). Taking Care of the Unexpected 2011 Odyssey 663