What this code means
B1079 may mean the vehicle has detected a problem in the daytime running light control or high-beam related lighting circuit handled by the MICU.
What the vehicle may do
- The daytime running lights may not operate as expected.
- High-beam operation may be affected or may be useful for diagnosis.
- The concern can be intermittent if the code does not reset during verification.
Possible fault areas
- Possible fuse or protected-feed issue.
- Possible high-beam bulb issue.
- Possible MICU or under-dash fuse and relay box control issue.
- Possible open, high resistance, connector, or ground issue in the high-beam lighting circuit.
Diagnostic path
Opening context
On this 2010 to 2015 Honda Civic with the 1.8 gas engine, B1079 points us toward a daytime running light malfunction handled through the MICU and the high-beam lighting circuit. In plain terms, the daytime running lights may not work normally, and the high beams may also be part of what you need to check. The likely areas are basic power protection, the high-beam bulbs, the MICU inside the under-dash fuse and relay box, and the left, right, and ground side wiring. We’re going to stay in order and prove each part of the circuit before making the call.
Confirm the code first
Start by verifying the problem. Turn the headlight switch OFF and apply the parking brake. Clear the codes with the HDS. Then release the parking brake, turn the ignition switch to LOCK (0), and turn it back to ON (II). Check codes again with the HDS. If B1079 comes right back, continue with the circuit checks. If it does not come back, treat it as an intermittent at this point. The system is OK right now, so look closely for loose or poor connections rather than forcing a failure that is not present.
Check the protected feeds
Next, turn the ignition switch to LOCK (0) and check the two fuses for this circuit in the under-dash fuse and relay box: No. B38 (10 A) and No. B39 (10 A). If both fuses are OK, move on to the high-beam operation check. If either fuse is not OK, replace the fuse. If it blows again, repair a short to ground on the No. B38 (10 A) or No. B39 (10 A) fuse circuit, depending on which side is affected.
Use high-beam operation to judge the MICU path
Now turn the headlight high beams ON and see whether both high beams come on. If both high beams work, the circuit has enough function to point back toward a faulty MICU, and the supported repair is to replace the under-dash fuse and relay box. If both high beams do not come on, keep going and check the bulbs before condemning the control side.
Check the high-beam bulbs
Check the high-beam bulbs themselves. If the bulbs are OK, continue into the open-circuit checks. If a high-beam bulb is faulty, replace the faulty bulb. This keeps the diagnosis grounded in the simple load check before you start chasing wiring.
Check the left high-beam feed wire
For the left-side feed check, keep the ignition at LOCK (0). Disconnect the under-dash fuse and relay box connector C (38P), the left high-beam 2P connector, and the right high-beam 2P connector. Check continuity on the L_H/L_HI circuit between under-dash fuse and relay box connector C (38P) terminal No. 18, PNK, and the left high-beam 2P connector terminal No. 1, PNK. If you have continuity, go on to the right-side feed. If you do not, repair an open or high resistance in that wire.
Check the right high-beam feed wire
With the same connectors still disconnected and the ignition still at LOCK (0), check the R_H/L_HI circuit. Measure continuity between under-dash fuse and relay box connector C (38P) terminal No. 14, WHT, and the right high-beam 2P connector terminal No. 1, WHT. If continuity is good, move to the ground-side check. If continuity is missing, repair an open or high resistance in that wire.
Check the high-beam grounds
Last, check the ground side. With the ignition at LOCK (0), connector C (38P) disconnected, and both high-beam 2P connectors disconnected, check continuity from each high-beam connector terminal No. 2, BLK, to body ground. Do the left and right sides individually. If the ground continuity is good, the path again points to a faulty MICU, and the supported repair is to replace the under-dash fuse and relay box. If ground continuity is not good, repair an open or high resistance in the ground wire, or a poor ground at G201 or G301.
Takeaway
The key with B1079 is to separate a real MICU problem from a basic fuse, bulb, feed-wire, or ground fault. Confirm the code first, check the fuses, prove high-beam operation, then test the left feed, right feed, and grounds in order. For more diagnostic training, visit stepdiagnostics.com.
Final check
B1079 is best approached as an electrical circuit diagnosis: confirm the code, check power protection and loads, then prove the feed and ground paths before calling the control unit.
For more guided automotive diagnostics, visit STEP Diagnostics.
