DTC Troubleshooting: B1279
DTC B1279:
 DIMMER Switch Circuit Malfunction
  1. Clear the DTCs with the HDS.
  1. Turn the ignition switch OFF, and then back ON (II).
  1. Turn the headlight switch ON.
  1. Change the dimmer switch from low beam to high beam.
  1. Turn the headlight switch OFF.
  1. Pull and hold the combination light switch lever, and hold the passing switch position.
  1. Check for DTCs with the HDS.
Is DTC B1279 indicated?
YES -
Go to Step 8 .
NO -
Intermittent failure, the system is OK at this time. Check for loose or poor connections.■
  1. Select the BODY ELECTRICAL system select menu, then enter the LIGHTING SYSTEM.
  1. Check each combination light switch position value with the DATA LIST menu.

    When the passing switch operated

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


    When the headlight ON and dimmer switch changed

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

Are all data list values correct?
YES -
NO -
Go to Step 10 .
  1. Turn the ignition switch OFF.
  1. Disconnect the combination light switch 12P connector.
  1. Turn the ignition switch ON (II).
  1. Select the BODY ELECTRICAL system select menu, then enter the LIGHTING SYSTEM.
  1. Check each combination light switch position value with the DATA LIST menu.

    When the combination light switch is OFF

    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 18 .
NO -
Go to Step 15 .
  1. Turn the ignition switch OFF.
  1. Disconnect the under-dash fuse/relay box connector S (20P).
  1. Check for continuity between body ground and the under-dash fuse/relay box connector S (20P) No. 11, No. 12, and No. 16 terminals.
Is there continuity?
YES -
Repair a short to ground in the wire.■
NO -
  1. Turn the ignition switch OFF.
Is the combination light switch OK?
YES -
Go to Step 20 .
NO -
Replace the combination light switch.■
  1. Disconnect the under-dash fuse/relay box connector S (20P).
  1. Check for continuity between the under-dash fuse/relay box connector S (20P) No. 1, No. 5, No. 11, and No. 13 terminals and the combination light switch 12P connector No. 9, No. 10, No. 11, and No. 12 terminals respectively.
Is there continuity?
YES -
NO -
Repair an open in the wire.■