B1279

Control System DTCs

DTC Troubleshooting: B1279

DTC B1279 : Dimmer Switch Circuit Malfunction

NOTE: Refer to the Electrical Wiring Diagrams for the location of the under-dash fuse/relay box connectors.

1. Exterior lights system check 1:

Exterior lights system check 1
-1. With the headlight dimmer switch in the neutral position, select LIGHTING from the BODY ELECTRICAL SYSTEM SELECT menu, and enter the DATA LIST.

-2. Check the ON/OFF information of the HEADLIGHT SWITCH (HIGH BEAM) and HEADLIGHT SWITCH (PASSING) in the DATA LIST.

Is either information indicator ON?
-YES- Go to step 4.
-NO- Go to step 2.

2. Exterior lights system check 2:

Exterior lights system check 2
-1. With the headlight dimmer switch in the high beam position, check the ON/OFF information of the HEADLIGHT SWITCH (HIGH BEAM) and HEADLIGHT SWITCH (PASSING) in the DATA LIST.

Are both information indicators ON?
-YES- Go to step 3.
-NO- Intermittent failure, the system is OK at this time.

3. Shorted wire check (H/L_HI_SW to PASSING_SW line):

Shorted wire check (H/L_HI_SW to PASSING_SW line)
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.





-3. Connect terminals A and B with a jumper wire.









-4. Check the ON/OFF information of the HEADLIGHT SWITCH (HIGH BEAM) and HEADLIGHT SWITCH (PASSING) in the DATA LIST.

Are both information indicators ON?
-YES- Repair a short between the wires.
-NO- Replace the combination light switch.

4. Determine possible failure area (combination light switch, others):

Determine possible failure area (combination light switch, others)
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.





-3. Check the ON/OFF information of the HEADLIGHT SWITCH (HIGH BEAM) and HEADLIGHT SWITCH (PASSING) in the DATA LIST.

Is either information indicator ON?
-YES- Go to step 5.
-NO- Replace the combination light switch Service and Repair.

5. Shorted wire check (PASSING_SW, H/L_HI_SW lines):

Shorted wire check (PASSING_SW, H/L_HI_SW lines)
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.





-3. Check for continuity between test points 1 and 2 individually.














Is there continuity?
-YES- Repair a short to ground in the wire.
-NO- Faulty MICU; replace the under-dash fuse/relay box Service and Repair.