B1278

DTC B1278: Headlight Switch ON Position Circuit Malfunction

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A.

1. Clear the DTCs with the HDS.
2. Turn the ignition switch OFF, and then back ON (II), and wait for 2 seconds.
3. Turn the parking (SMALL) light switch ON and wait for 2 seconds.
4. Turn the headlight switch (LOW) ON and wait for 2 seconds.
5. Change the dimmer switch position from low beam to high beam and wait for 2 seconds.
6. Check for DTCs with the HDS.

Is DTC B1278 indicated?

YES - Go to step 7.

NO - Intermittent failure, the headlight switch and the combination switch control unit are OK at this time. Check for loose or poor connections at the headlight switch connector, and at the combination switch connector.

7. With the headlight switch in the HEADLIGHT position, select LIGHTING SYSTEM with the HDS, and enter DATA LIST.
8. Check the ON/OFF information of the HEADLIGHT SWITCH ON in the DATA LIST.

Is the information indicator ON, and change to OFF when the headlight switch is put to the OFF and the PARKING positions?

YES - Faulty combination switch control unit. Replace the combination switch.

NO - Go to step 9.

9. Do the headlight switch test.

Is the headlight switch test OK?

YES - Repair the wire between the No. 3 terminal of the headlight switch 6P connector and the No. 10 terminal of the combination switch 12P connector.

NO - Replace the headlight switch.