It's exact CFM meaning will be in the service manual but for other vehicles P2189* code stands for “System too lean at idle,” which means the air-fuel mixture during idle has too much air and not enough fuel. Possible causes of the P2189 code include a faulty oxygen sensor, faulty gas cap seal, and a loose oil filler cap. Decreased engine performance, difficulty starting, and irregular idle are common symptoms of the P2189 code.