What does 'System too rich at idle - Bank 1' mean?

[McLukas]

System too rich at idle - Bank 1 indicates that the vehicle's air-fuel mixture is too rich. The inspection items include: 1. Actual working values of the oxygen sensor; 2. Check for any air leaks in the engine intake system; 3. Inspect oxygen sensor wiring for poor connections that may cause signal deviations during operation; 4. Check for excessive engine carbon deposits, cleaning if necessary. Vehicle idle refers to an operating condition where the engine runs without load, only overcoming internal mechanical friction without delivering power output. It represents the minimum stable operating speed, which can be adjusted by modifying throttle opening and idle fuel supply.