Question

What does the P2189 code mean for my 2005 Land Rover Range Rover V8?

Answer 1

It means your fuel to air ratio mix in the engine is uneven, in the sense that your engine is sucking in more air or the fuel  is more than required to the regulated ratio it needs. , alternately your engine might be sucking in air from a source other than the maf e.g a vacuum line...