DTC Troubleshooting: B1279
DTC B1279: Dimmer switch circuit malfunction
DTC Description
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.

1.
Exterior lights system check 1:

Exterior lights system check 1
?1.
Turn the vehicle to the ON mode.

?2.
With the headlight dimmer switch in the neutral position, check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Headlight Switch (HIGH BEAM)
    
Headlight Switch (PASSING)
    

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 parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Headlight Switch (HIGH BEAM)
    
Headlight Switch (PASSING)
    

Are both information indicators ON at the same time?

     
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 vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Combination light switch 12P connector

?3.
Connect terminals A and B with a jumper wire.
Terminal A
Under-dash fuse/relay box connector B (20P) No. 3
Terminal B
Body ground

?4.
Turn the vehicle to the ON mode.

?5.
Check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Headlight Switch (HIGH BEAM)
    
Headlight Switch (PASSING)
    

Are both information indicators ON at the same time?

     
YES
     
     
     
Repair a short between the wires.?
     
NO
     
     
     
The H/L HI SW to PASSING SW wire is OK. 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 vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Combination light switch 12P connector

?3.
Turn the vehicle to the ON mode.

?4.
Check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Headlight Switch (HIGH BEAM)
    
Headlight Switch (PASSING)
    

Is either information indicator ON?

     
YES
     
     
     
Go to step 5.
     
NO
     
     
     
5.
Shorted wire check (PASSING SW, H/L HI SW lines):

Shorted wire check (PASSING SW, H/L HI SW lines)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
Under-dash fuse/relay box connector B (20P)

?3.
Check for continuity between test points 1 and 2 individually.
Test condition
Vehicle OFF (LOCK) mode
Combination light switch 12P connector: disconnected
Under-dash fuse/relay box connector B (20P): disconnected
Test point 1
Under-dash fuse/relay box connector B (20P) No. 12
Test point 2
Body ground

Test point 1
Under-dash fuse/relay box connector B (20P) No. 3
Test point 2
Body ground

Are there continuity?

     
YES
     
     
     
Repair a short to ground in the wire.?
     
NO
     
     
     
The PASSING SW and H/L HI SW wires are OK. Faulty MICU; replace the under-dash fuse/relay box.?