DTC Troubleshooting: B1279DTC 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), or press the engine start/stop button to select the OFF mode and then the ON mode.
3.
Turn the combination light (headlight) switch ON.
4.
Change the dimmer switch from low beam to high beam.
5.
Turn the combination light switch OFF, and then to the passing position.
6.
Wait for at least 6 seconds.
7.
Check for DTCs with the HDS.
Is DTC B1279 indicated?
YES -
Go to step 8.
NO -
Intermittent failure, the system is OK at this time. Check for loose or poor connections.
8.
Select LIGHTING from the BODY ELECTRICAL SYSTEM SELECT menu, then enter the DATA LIST.
9.
Check each combination light switch position value with the DATA LIST menu.
When the passing switch is operatedWhen the headlight switch is turned ON, and the dimmer switch changed from low beam to high beamAre all data list values correct?
YES -
Faulty driver's MICU; replace the driver's under-dash fuse/relay box
Drivers Under-Dash Fuse/Relay Box (Drivers MICU) Removal and Installation.
NO -
Go to step 10.
10.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.
11.
Disconnect the combination light switch 12P connector.
12.
Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.
13.
Select LIGHTING from the BODY ELECTRICAL SYSTEM SELECT menu, then enter the DATA LIST.
14.
Check each combination light switch position value with the DATA LIST menu.
Are all data list values indicated OFF?
YES -
Go to step 18.
NO -
Go to step 15.
15.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.
16.
Disconnect under-dash fuse/relay box connector R (24P).
17.
Check for continuity between body ground and driver's under-dash fuse/relay box connector R (24P) terminals No. 8,No. 21, and No. 22 individually.
Is there continuity?
YES -
Repair a short to ground in the wire(s).
NO -
Faulty driver's MICU; replace the driver's under-dash fuse/relay box
Drivers Under-Dash Fuse/Relay Box (Drivers MICU) Removal and Installation.
18.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.
19.
Do the combination light switch test
Service and Repair.
Is the combination light switch OK?
YES -
Go to step 20.
NO -
Replace the combination light switch
Service and Repair.
20.
Disconnect driver's under-dash fuse/relay box connector R (24P).
21.
Check for continuity between driver's under-dash fuse/relay box connector R (24P) terminals and the combination light switch 12P connector terminals as shown:
Is there continuity?
YES -
Go to step 22.
NO -
Repair an open or high resistance in the wire(s).
22.
Check for continuity between driver's under-dash fuse/relay box connector R (24P) terminals as shown:
Is there continuity?
YES -
Repair a short between the wires.
NO -
Faulty driver's MICU; replace the driver's under-dash fuse/relay box
Drivers Under-Dash Fuse/Relay Box (Drivers MICU) Removal and Installation.
