If you are investigating rough running after air-filter service, save every stored and pending code before clearing anything. Compare airflow readings and fuel trims only against vehicle-specific expectations. Record the engine temperature and load alongside the reading; the same value can mean different things in different conditions.
A basic reader may not access every module. Check that the airbox is closed and intake duct or sensor connectors are fully seated. Use the exact vehicle’s service information to interpret the result.
Quick educational note
For information, not a diagnosis or repair instruction. Vehicle-specific checks are still required. Consult the manufacturer's guidance and a qualified technician.
How to use this information
This article explains general principles and does not establish what is wrong with your vehicle. Read the content limitations.