DTC B1279: Dimmer Switch Circuit Malfunction

WARNING: This page is about a different car, the 2011 Honda Insight and 2010 Honda Insight. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0) and then back to ON (II).
Turn the combination light (headlight) switch ON.
Change the dimmer switch from low beam to high beam.
Turn the combination light switch OFF and then to the passing position.
Check for DTCs with the HDS.
Is DTC B1279 indicated?

YES -Go to step 7.

NO -Intermittent failure, the system is OK at this time. Wiggle the related harness, and check for loose or poor connections.
Select LIGHTING from the BODY ELECTRICAL system select menu, and enter the DATA LIST.

Check each combination light switch position value with the DATA LIST menu.

When the passing switch is operated

DATA LIST

Data List	Value
Headlight Switch (PASSING)	ON
Headlight Switch (High beam)	OFF

When the headlight switch is turned ON, and the dimmer switch is changed from low beam to high beam

DATA LIST

Data List	Value
Headlight Switch (PASSING)	OFF
Headlight Switch (High beam)	ON
Headlight Switch (HEADLIGHT)	ON

Are all data list values correct?

YES -Faulty MICU; replace the under-dash fuse/relay box.

USA models (see REMOVAL AND INSTALLATION ).
Canada models (see CANADA MODELS ).

NO -Go to step 9.

Turn the ignition switch to LOCK (0).
Disconnect the combination light switch 12P connector.
Turn the ignition switch to ON (II).
Select LIGHTING from the BODY ELECTRICAL system select menu, and enter the DATA LIST.

Check each combination light switch position value with the DATA LIST menu.

DATA LIST

Data List	Value
Headlight Switch (PASSING)	OFF
Headlight Switch (High beam)	OFF
Headlight Switch (HEADLIGHT)	OFF

Are all data list values indicated OFF?

YES -Go to step 17.

NO -Go to step 14.

Turn the ignition switch to LOCK (0).
Disconnect under-dash fuse/relay box connector M (34P).
Check for continuity between body ground and under-dash fuse/relay box connector M (34P) terminals No. 3, No. 4, and No. 5 individually.

Fig 1: Checking Continuity Between Body Ground And Under-Dash Fuse/Relay Box Connector M (34P) Terminals No. 3, No. 4, And No. 5

Is there continuity?

YES -Repair a short to ground in the wire.

NO -Faulty MICU; replace the under-dash fuse/relay box.
- USA models (see REMOVAL AND INSTALLATION ).
- Canada models (see CANADA MODELS ).
Turn the ignition switch to LOCK (0).
Do the combination light switch test (see COMBINATION LIGHT SWITCH TEST/REPLACEMENT ).
Is the combination light switch OK?

YES -Go to step 19.

NO -Replace the combination light switch.
Disconnect under-dash fuse/relay box connector M (34P).

Check for continuity between the under-dash fuse/relay box connector M (34P) terminals and the combination light switch 12P connector terminals as shown:

COMBINATION LIGHT SWITCH 12P CONNECTOR CHART

Under-dash fuse/relay box connector M (34P)	Combination light switch 12P connector
3	4
4	6
5	10
33	12

Fig 2: Checking Continuity Between Under-Dash Fuse/Relay Box Connector M (34P) Terminals And Combination Light Switch 12P Connector Terminals

Is there continuity?

YES -Go to step 21.

NO -Repair an open in the wire.

Check for continuity between the under-dash fuse/relay box connector M (34P) terminals as shown:

TERMINAL SPECIFICATIONS

From terminal	To terminal
5	3,4,7,8,33
7	3,4,8,33
8	3,4,33

Is there continuity?

YES -Repair a short between the wires.

NO -Faulty MICU; replace the under-dash fuse/relay box.

USA models (see REMOVAL AND INSTALLATION ).
Canada models (see CANADA MODELS ).