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DTC B1279: DIMMER Switch Circuit Malfunction

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).
  1. Clear the DTCs with the HDS.
  2. Turn the ignition switch to LOCK (0), and then back to ON (II).
  3. Turn the combination light (headlight) switch ON.
  4. Change the dimmer switch from low beam to high beam.
  5. Turn the combination light switch OFF, and then to the passing position, and wait for at least 6 seconds.
  6. Check for DTCs with the HDS.

    Is DTC B1279 indicated? 

    YES  -Go to step 7.

    NO  -Intermittent failure, the system is OK at this time. Check for loose or poor connections.

  7. Select LIGHTING from the BODY ELECTRICAL SYSTEM SELECT menu, then enter DATA LIST.
  8. Check each combination light switch position value with the DATA LIST menu.

    When the passing switch is operated 

    COMBINATION LIGHT SWITCH POSITION VALUE CHART

    Data List Value
    Headlight Switch (PASSING) ON
    Headlight Switch (High beam) OFF

    When the headlight switch is turned ON, and the dimmer switch changed from low beam to high beam 

    COMBINATION LIGHT SWITCH POSITION VALUE CHART

    Data List Value
    Headlight Switch (PASSING) OFF
    Headlight Switch (High beam) ON
    Headlight Switch (HEADLIGHT) ON

    Are all data list values correct? 

    YES  -Faulty driver's MICU; replace the driver's under-dash fuse/relay box, USA models (see DRIVER'S UNDER-DASH FUSE/RELAY BOX (MICU)REMOVAL AND INSTALLATION ), Canada models (see SPECIAL TOOLS REQUIRED ).

    NO  -Go to step 9.

  9. Turn the ignition switch to LOCK (0).
  10. Disconnect the combination light switch 12P connector.
  11. Turn the ignition switch to ON (II).
  12. Select LIGHTING from the BODY ELECTRICAL SYSTEM SELECT menu, then enter DATA LIST.
  13. Check each combination light switch position value with the DATA LIST menu.

    When the combination light switch is turned OFF 

    COMBINATION LIGHT SWITCH POSITION VALUE CHART

    Data List Value
    Headlight Switch (PASSING) OFF
    Headlight Switch (High beam) OFF
    Headlight Switch (HEADLIGHT) OFF

    Are all data list values indicated OFF? 

    YES  -Go to step  17.

    NO  -Go to step 14.

  14. Turn the ignition switch to LOCK (0).
  15. Disconnect driver's under-dash fuse/relay box connector R (24P).
  16. Check for continuity between body ground and driver's under-dash fuse/relay box connector R (24P) terminals No. 8, No. 21, and No. 22 individually.

    DRIVER'S UNDER-DASH FUSE/RELAY BOX CONNECTOR R (24P) 

    Fig 1: Identifying Driver'S Under-Dash Fuse/Relay Box Connector R (24P)
    G07770481Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair a short to ground in the wire.

    NO  -Faulty driver's MICU; replace the driver's under-dash fuse/relay box, USA models (see DRIVER'S UNDER-DASH FUSE/RELAY BOX (MICU)REMOVAL AND INSTALLATION ), Canada models (see SPECIAL TOOLS REQUIRED ).

  17. Turn the ignition switch to LOCK (0).
  18. Do the combination light switch test (see COMBINATION LIGHT SWITCH TEST/REPLACEMENT ).

    Is the combination light switch OK? 

    YES  -Go to step 19.

    NO  -Replace the combination light switch (see COMBINATION LIGHT SWITCH TEST/REPLACEMENT ).

  19. Disconnect driver's under-dash fuse/relay box connector R (24P).
  20. Check for continuity between driver's under-dash fuse/relay box connector R (24P) terminals and the combination light switch 12P connector terminals as shown:
    CONNECTOR TERMINALS REFERENCE CHART

    Driver's under-dash fuse/relay box connector R (24P) Combination light switch 12P connector
    3 (BLK) 12 (BLK)
    8 (BRN) 10 (BRN)
    21 (RED) 6 (RED)
    22 (LT BLU) 4(LT BLU)

    DRIVERS UNDER-DASH FUSE/RELAY BOX CONNECTOR R (24P) 

    Fig 2: Driver'S Under-Dash Fuse/Relay Box Connector R (24P)
    G07770482Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Go to step 21.

    NO  -Repair an open or high resistance in the wire.

  21. Check for continuity between driver's under-dash fuse/relay box connector R (24P) terminals as shown:
    CONNECTOR TERMINALS REFERENCE CHART

    From terminal To terminal
    21 (RED) 6 (RED)
    7 (GRY)
    8 (BRN)
    22 (LT BLU)
    22 (LT BLU) 6 (RED)
    7 (GRY)
    8 (BRN)

    Is there continuity? 

    YES  -Repair a short between the wires.

    NO  -Faulty driver's MICU; replace the driver's under-dash fuse/relay box, USA models (see DRIVER'S UNDER-DASH FUSE/RELAY BOX (MICU)REMOVAL AND INSTALLATION ), Canada models (see SPECIAL TOOLS REQUIRED ).

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