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Control Unit Input Test

  1. Before testing, troubleshoot the multiplex control system (see TROUBLESHOOTING ).
  2. Remove the driver's multiplex control unit from the driver's under-dash fuse/relay box.
  3. Inspect the connector and socket terminals to be sure they are all making good contact.
    • If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.
    • If the terminals look OK, go to step 4.
    Fig 1: Identifying Driver's Multiplex Control Unit Connector Terminals
    G03642104Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 2: Identifying Driver's Multiplex Control Unit Connector B Terminals
    G03642105Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 3: Identifying Driver's Under-Dash Fuse/relay Box Connector E Terminals
    G03642106Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 4: Identifying Driver's Under-Dash Fuse/relay Box Connector K Connector Terminals
    G03642107Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 5: Identifying Driver's Under-Dash Fuse/relay Box Connector M Connector Terminals
    G03642108Courtesy of AMERICAN HONDA MOTOR CO., INC.
  4. With the driver's multiplex control unit still disconnected, make these input tests at the connector and driver's under-dash fuse/relay box sockets.
    • If any test indicates a problem, find and correct the cause, then recheck the system.
    • If all the input tests prove OK, go to step 5.
    CONNECTOR AND DRIVER'S UNDER-DASH FUSE/RELAY BOX

    Cavity Wire Test condition Test: Desired result Possible cause if result is not obtained
    A24 Fuse/relay box socket Ignition switch ON (II) Check for voltage to ground: There should be battery voltage.
    • Blown No. 9 (10 A) fuse in the driver's under-dash fuse/relay box
    • Faulty driver's fuse/relay box
    A12 Under all conditions Check for voltage to ground: There should be battery voltage.
    • Blown No. 13 (7.5 A) fuse in the passenger's under-dash fuse/ relay box
    • An open in the wire
    A1 Under all conditions Attach to ground: The ignition key light should come on.
    • Blown No. 47 (20 A) fuse in the under-hood fuse/relay box
    • An open in the wire
    B11(1) BLK Under all conditions Check for continuity to ground: There should be continuity.
    • Poor ground (G501)
    • An open in the wire
    B17(1) YEL/RED Ignition switch OFF Check for continuity to ground: There should be continuity.
    • Faulty engine oil pressure switch
    • An open in the wire
    Ignition switch ON (II) Check the low engine oil pressure indicator operation: The indicator should come on.
    • Faulty LED
    • An open in the wire
    Start the engine. Check for voltage to ground: There should be battery voltage.
    • Insufficient oil
    • Improper lubrication
    • Faulty engine oil pressure switch
    • An open in the wire
    • A short in the wire
    (1) Multiplex control unit connector B
  5. Reconnect the driver's multiplex control unit to the driver's under-dash fuse/relay box, and perform the following input tests at the appropriate connectors on the back of the driver's under-dash fuse/relay box. For driver's under-dash fuse/relay box connector socket location (see DRIVER'S UNDER-DASH FUSE/RELAY BOX ).
    • If any test indicates a problem, find and correct the cause, then recheck the system.
    • If all the input tests prove OK, the driver's multiplex control unit must be faulty, replace it.
    DRIVER'S MULTIPLEX CONTROL UNIT TO THE DRIVER'S UNDER-DASH FUSE/RELAY BOX

    Cavity Wire Test condition Test: Desired result Possible cause if result is not obtained
    E3 GRN/ORN Driver's door open Check for voltage to ground: There should be less than 1 V.
    • Faulty driver's door switch
    • An open in the wire
    Driver's door closed Check for voltage to ground: There should be 5 V or more.
    • Faulty driver's door switch
    • Short to ground
    K12(2) BLU/RED Ignition switch ON (II), driver's seat belt unbuckled Check for voltage to ground: There should be less than 1 V.
    • Faulty driver's seat belt switch
    • Poor ground (G601)
    • An open in the wire
    Ignition switch ON (II), driver's seat belt buckled Check for voltage to ground: There should be 5 V or more.
    • Faulty driver's seat belt switch
    • Short to ground
    M9 BLU/WHT Ignition key is in the ignition switch Check for voltage to ground: There should be less than 1 V.
    • Faulty ignition switch
    • Poor ground (G401)
    • An open in the wire
    Ignition key is out of the ignition switch Check for voltage to ground: There should be 5 V or more.
    • Faulty ignition switch
    • Short to ground
    B5(1) WHT/BLU Engine running Check for voltage to ground: There should be battery voltage.
    • Faulty charging system
    • An open in the wire
    • Short to ground
    M3 RED/BLK Combination light switch ON Check for voltage to ground: There should be battery voltage.
    • Blown No. 10 (15 A) fuse in the passenger's under-dash fuse/relay box
    • Faulty taillight relay
    • Faulty combination light switch
    • Faulty driver's under-dash fuse/ relay box
    • An open in the wire
    (1) Multiplex control unit connector B
    (2) '03 model
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