DTC Troubleshooting: B1278
DTC B1278:
 Combination Light Switch ON Position Circuit Malfunction
  1. Clear the DTCs with the HDS.
  1. Turn the ignition switch OFF, and then back ON (II).
  1. Operate each combination light switch position, then turn the combination light switch OFF.
  1. Check for DTCs with the HDS.
Is DTC B1278 indicated?
YES -
Go to Step 5 .
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 combination light switch turns OFF

    Data List
    Value
    Headlight Switch (OFF)
    ON
    Headlight Switch (PARKING)
    OFF
    Headlight Switch (AUTO)
    OFF
    Headlight Switch (HEADLIGHT)
    OFF


    When the combination light switch turns PARKING

    Data List
    Value
    Headlight Switch (OFF)
    OFF
    Headlight Switch (PARKING)
    ON
    Headlight Switch (AUTO)
    OFF
    Headlight Switch (HEADLIGHT)
    OFF


    When the combination light switch turns AUTO

    Data List
    Value
    Headlight Switch (OFF)
    OFF
    Headlight Switch (PARKING)
    ON
    Headlight Switch (AUTO)
    ON
    Headlight Switch (HEADLIGHT)
    ON


    When the combination light switch turns ON (headlight)

    Data List
    Value
    Headlight Switch (OFF)
    OFF
    Headlight Switch (PARKING)
    ON
    Headlight Switch (AUTO)
    OFF
    Headlight Switch (HEADLIGHT)
    ON

Are all data list values correct?
YES -
NO -
Go to Step 7 .
  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 (OFF)
    OFF
    Headlight Switch (PARKING)
    OFF
    Headlight Switch (HEADLIGHT)
    OFF

Are all data list values indicated OFF?
YES -
Go to Step 15 .
NO -
Go to Step 12 .
  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. 1, No. 11, and No. 13 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 17 .
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.■