What this code means
B1276 may indicate that the MICU is seeing a headlight switch position signal that does not match the expected combination light switch state.
What the vehicle may do
- Exterior lighting may not respond as expected to switch position.
- The concern may only appear in scan-tool switch data.
- The issue can be intermittent if connections are loose or poor.
Possible fault areas
- Possible combination light switch fault.
- Possible short to ground, open, or high resistance in the switch signal wiring.
- Possible issue in the switch ground path.
- Possible MICU or under-dash fuse/relay box involvement.
Diagnostic path
Code overview and diagnostic direction
On this 2010 to 2015 Honda Civic, B1276 points to the headlight switch position circuit in the body electrical lighting system. In plain terms, the MICU may be seeing a combination light switch input that does not match the switch position. The vehicle may have exterior lighting behavior that does not line up with the switch, or the problem may only show up in scan-tool data. The broad possible fault areas are the combination light switch, the switch signal wiring, the switch ground path, and the MICU in the under-dash fuse/relay box. We are going to diagnose it by watching the switch inputs, then separating a switch fault from a wiring fault or MICU fault.
Start by verifying the switch data
Start in the lighting data list and watch the combination light switch inputs while moving the switch through OFF, PARKING, AUTO, and ON, headlight. With the switch OFF, Headlight Switch OFF should read ON, and PARKING, AUTO, and HEADLIGHT should read OFF. In PARKING, OFF should read OFF, PARKING should read ON, AUTO should read OFF, and HEADLIGHT should read OFF. In AUTO, all four listed inputs should read OFF. In ON, headlight, OFF should read OFF, PARKING should read ON, AUTO should read OFF, and HEADLIGHT should read ON. If all of those values are correct, treat it as an intermittent failure for now. The system is OK at this time, so check for loose or poor connections. If the values are not correct, keep going with the circuit checks.
Decide whether the input is stuck OFF or stuck ON
Next, check the combination light switch data list value again. The key question here is whether the value is OFF, not ON. If the suspect data value is OFF, move ahead to the jumper test at the switch connector. If it is not OFF, continue by disconnecting the switch so you can see whether the switch itself is pulling that input on.
If the value is stuck ON, isolate the switch first
Turn the ignition switch to LOCK (0), then disconnect the combination light switch 12P connector. Go back to the data list and see whether the value changes from ON to OFF. If it does change from ON to OFF with the switch disconnected, the diagnostic path calls the combination light switch faulty. If it does not change, the switch is not the reason that input is staying on, so move to the short-to-ground check between the switch circuits and the MICU connector.
Check the switch signal wires for a short to ground
For the shorted-wire check, leave the ignition switch in LOCK (0). The combination light switch 12P connector stays disconnected, and you also disconnect under-dash fuse/relay box connector T (20P). Then check continuity to body ground on each of the switch signal lines individually: H/L_OFF_SW from connector T (20P) No. 1, ORN, to body ground; H/L_ON_SW from connector T (20P) No. 2, PNK, to body ground; and PARKING_LT_SW from connector T (20P) No. 3, GRY, to body ground. If there is continuity, repair the short to ground in the wire. If there is no continuity on that path, the diagnostic result is a faulty MICU, and the repair path is to replace the under-dash fuse/relay box.
If the value is stuck OFF, simulate the switch input
If the earlier data list value was OFF, use a jumper wire at the combination light switch 12P connector to ground the switch inputs one at a time. Connect connector No. 1, ORN, to body ground. Then connector No. 7, PNK, to body ground. Then connector No. 8, GRY, to body ground. Watch the data list while you do this. If the value changes from OFF to ON, the wiring and MICU side responded, so the diagnostic path calls the combination light switch faulty. If the value does not change from OFF to ON, continue to the open-wire and high-resistance check.
Check for an open or high resistance in the switch circuits
For the open-wire check, turn the ignition switch to LOCK (0) and disconnect under-dash fuse/relay box connector T (20P). Now check continuity end to end on the switch circuits. Check H/L_OFF_SW between connector T (20P) No. 1, ORN, and combination light switch 12P connector No. 1, ORN. Check H/L_ON_SW between connector T (20P) No. 2, PNK, and combination light switch 12P connector No. 7, PNK. Check PARKING_LT_SW between connector T (20P) No. 3, GRY, and combination light switch 12P connector No. 8, GRY. Then check COMBI_SW_GND (LT) between connector T (20P) No. 5, BLK, and combination light switch 12P connector No. 6, BLK. If continuity is present where checked, the diagnostic result is a faulty MICU, and the repair path is to replace the under-dash fuse/relay box. If continuity is not present, repair the open or high resistance in the wire.
Verification and takeaway
After the repair, keep verification separate from the fault isolation work. Repeat the original data-list check through OFF, PARKING, AUTO, and ON, headlight, and confirm the values now match the switch positions. The takeaway on B1276 is simple: do not guess at the switch or the MICU. Use the data list first, then use disconnect, jumper, short-to-ground, and continuity checks to prove which side of the circuit is wrong. For more diagnostic training, visit stepdiagnostics.com.
Final check
B1276 is best approached by proving the switch input on the data list, then using connector isolation and continuity checks to separate switch, wiring, and MICU faults.
For more guided automotive diagnostics, visit STEP Diagnostics.
