B1279

DTC Troubleshooting: B1279

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 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 switch ON.

4. Change the DIMMER switch from low beam to high to the beam.

5. Turn the combination light switch OFF, and then to the PASSING position.

6. Check the DTCs with the HDS.

Is DTC B1279 indicated?

YES -

Go to step 7.

NO -

Intermittent failure. The lighting system is OK at this time. Wiggle the related harness, and check for loose or poor connections.�

7. Select LIGHTING from the BODY ELECTRICAL menu, and enter DATA LIST.

8. Check the ON/OFF information of the HEADLIGHT SWITCH (HEADLIGHT), HEADLIGHT SWITCH (HIGH BEAM) and HEADLIGHT SWITCH (PASSING).

Are the HEADLIGHT SWITCH (HIGH BEAM) information indicator ON, HEADLIGHT SWITCH (PASSING) information indicator ON with the combination light switch in DIMMER position, and are the HEADLIGHT SWITCH (HEADLIGHT) information indicator OFF, HEADLIGHT SWITCH (HIGH BEAM) information indicator OFF and HEADLIGHT SWITCH (PASSING) information indicator OFF with the combination light switch in ON position?

YES -

Faulty MICU; replace the under-dash fuse/relay box Under-Dash Fuse/Relay Box Removal/Installation.�

NO -

Go to step 9.

9. Disconnect the 12P connector from the combination light switch.

10. Check the ON/OFF information of the HEADLIGHT SWITCH (HEADLIGHT), HEADLIGHT SWITCH (HIGH BEAM) and HEADLIGHT SWITCH (PASSING) in the DATA LIST.

Are the information indicators OFF?

YES -

Go to step 14.

NO -

Go to step 11.

11. Turn the ignition switch to LOCK (0).

12. Disconnect under-dash fuse/relay box connector S (20P).

13. Check for continuity between body ground and under-dash fuse/relay box connector S (20P) terminals No. 11, No. 12, and No. 16 individually.





Is there continuity?

YES -

Repair a short to ground in the wire.�

NO -

Faulty MICU; replace the under-dash fuse/relay box Under-Dash Fuse/Relay Box Removal/Installation.�

14. Turn the ignition switch to LOCK (0).

15. Check the combination light switch Service and Repair.

Is the combination light switch OK?

YES -

Go to step 16.

NO -

Faulty combination light switch; replace it Service and Repair.�

16. Disconnect under-dash fuse/relay box connector S (20P).

17. Check for continuity between under-dash fuse/relay box connector S (20P) terminals No. 5, No. 11, No. 12, and No. 16 and the combination light switch 12P connector terminals No. 12, No. 10, No. 6, and No. 4 respectively.





Is there continuity?

YES -

Faulty MICU; replace the under-dash fuse/relay box Under-Dash Fuse/Relay Box Removal/Installation.�

NO -

Repair an open or high resistance in the wire.�