That error means the engine is running too rich on Bank 1 — basically, it’s getting too much fuel or not enough air on the side of the engine where cylinder #1 is.
It could be caused by a few things like a dirty mass airflow sensor, a stuck fuel injector, a faulty oxygen sensor, or even something simple like a clogged air filter. If you have a scan tool, checking fuel trims and O2 sensor readings can help narrow it down. Otherwise, cleaning the MAF sensor and checking for any obvious air or fuel issues is a good start.
Let us know what engine or vehicle you’re working with and we'll do our best to assist you further ✌🏻
