What Honda A123 includes
- Replace engine oil (the A): The oil life monitor called this one done - unrelated to the other three items in this code.
- Reset the oil life monitor: Standard step after any A service, using the SEL/RESET control or dash menu.
- Rotate tires (the 1): Front tires wear faster on a front-wheel-drive Honda. Rotating keeps the set aging together.
- Replace engine air filter (the 2): A quick swap on most Civics, Accords and CR-Vs. A restricted filter costs fuel economy before it costs power.
- 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 oil life monitor.
A123 is four codes in one, and the largest A service this site tracks. A means change the engine oil. 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