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DTC Troubleshooting: B1279

DTC B1279:
 Dimmer Switch Circuit Malfunction
  1. Clear the DTCs with the HDS.
  1. Turn the ignition switch to LOCK (0) and then back to ON (II).
  1. Turn the combination light (headlight) switch ON.
  1. Change the dimmer switch from low beam to high beam.
  1. Turn the combination light switch OFF and then to the passing position.
  1. 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.■
  1. Select LIGHTING from the BODY ELECTRICAL system select menu, then enter the DATA LIST.
  1. Check each combination light switch position value with the DATA LIST menu.

    When the passing switch is operated

    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

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

Are all data list values correct?
YES -
NO -
Go to Step 9 .
  1. Turn the ignition switch to LOCK (0).
  1. Disconnect the combination light switch 12P connector.
  1. Turn the ignition switch to ON (II).
  1. Select LIGHTING from the BODY ELECTRICAL system select menu, then enter the DATA LIST.
  1. Check each combination light switch position value with the DATA LIST menu.

    When the combination light switch is turned 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 17 .
NO -
Go to Step 14 .
  1. Turn the ignition switch to LOCK (0).
  1. Disconnect under-dash fuse/relay box connector M (34P).
  1. Check for continuity between under-dash fuse/relay box connector M (34P) No. 3, No. 4, and No. 5 terminals and body ground individually.
Is there continuity?
YES -
Repair a short to ground in the wire.■
NO -
  1. Turn the ignition switch to LOCK (0).
Is the combination light switch OK?
YES -
Go to Step 19 .
NO -
Replace the combination light switch.■
  1. Disconnect under-dash fuse/relay box connector M (34P).

  1. Check for continuity between under-dash fuse/relay box connector M (34P) terminals and the combination light switch 12P connector terminals as shown:
    Under-dash fuse/relay box connector M (34P)
    Combination light switch 12P connector
    3
    3 [4]
    4
    1 [6]
    5
    9 [10]
    33
    7 [12]

    [ ]:
    LHD model

Is there continuity?
YES -
Go to Step 21 .
NO -
Repair an open in the wire.■
  1. Check for continuity between under-dash fuse/relay box connector M (34P) terminals as shown:
    From terminal
    To terminal
    5
    3, 4, 7, 8
    7
    3, 4, 8
    8
    3, 4

Is there continuity?
YES -
Repair a short between the wires.■
NO -
RHD model
LHD model