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Power Circuits

  1. Using a voltmeter, check for battery voltage between ECU power terminal and ground. See POWER & GROUND CIRCUITS TERMINAL IDENTIFICATION  table. See Fig 1. If battery voltage is not present, check appropriate ECU fuse in underhood fuse box. See ECU POWER CIRCUITS FUSE IDENTIFICATION  table. If fuse is okay, check for an open in wire between underhood fuse box and appropriate ECU power circuit terminal.
  2. Turn ignition switch to ON position. Using a voltmeter, check for battery voltage between appropriate ECU power circuit terminal and ground. See POWER & GROUND CIRCUITS TERMINAL IDENTIFICATION  table. See Fig 1. If battery voltage is not present, check appropriate fuse in underhood fuse box. See ECU POWER CIRCUITS FUSE IDENTIFICATION  table. If fuse is okay, check for an open in wire between fuse box and appropriate ECU power circuit terminal or check for a defective ignition switch.
    POWER & GROUND CIRCUITS TERMINAL IDENTIFICATION

    Application (1) ECU Terminal
    Ground Circuits A23, A24, A26 & B2
    Power Circuits
    Ignition Switch In
    OFF Position D1
    ON Position A25 & B1
    (1) For terminal location identification, see Fig 1.
    ECU POWER CIRCUITS FUSE IDENTIFICATION

    Application (1) Fuse
    Accord & Civic
    Ignition Switch In
    OFF Position BACK-UP
    ON Position ECU
    Prelude
    Ignition Switch In
    OFF Position CLOCK
    ON Position EFI/ECU
    (1) All fuses are in underhood fuse box.
    Fig 1: ECU Terminal ID
    G90C17139Courtesy of AMERICAN HONDA MOTOR CO., INC.
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