What Honda B123 includes
- Replace engine oil and filter (the B): The core of every B service. Honda specifies 0W-20 full synthetic on most modern models.
- Full inspection (also the B): Brakes front and rear, suspension, steering ends, fluid levels, driveshaft boots, fuel lines and exhaust.
- Rotate tires (the 1): Front tires wear faster on a front-wheel-drive Honda. Rotation evens the wear so the set ages together.
- Replace engine air filter (the 2): A restricted filter costs fuel economy before it costs power. A quick swap on most Civics, Accords and CR-Vs.
- Replace dust and pollen (cabin) filter (also the 2): Behind the glove box on most models. Weak vent airflow is the usual sign it is overdue.
- Replace transmission fluid (the 3): CVT fluid (a Honda-specific formulation) or conventional ATF depending on the model, plus transfer case fluid on AWD versions. Runs on its own mileage-based clock, separate from the other three items.
B123 is the largest B code this site tracks - everything in B12, plus transmission fluid. B means replace the engine oil and oil filter, plus a full mechanical inspection. 1 means rotate the tires. 2 means replace the engine air filter and the cabin filter, and inspect the drive belt. 3 means replace the transmission fluid, and the transfer case fluid too on all-wheel-drive models.
Every Honda Maintenance Minder code explained