code P0171 is a lean fuel trim usually caused by intake air leaks. ETM refers to the electronic throttle mechanism - which can get dirty over time (particularly if you don't service the air filter or drive in particularly dusty areas or have a clogged PCV which allows a mist of oil into the intake). Dirty ETMs are not very common on a 4 year old car. Not sure what you mean by "cooling odometer",

 

I had this on my '15 V60 when I got it in July. No CEL or symptoms, just happened to find it when testing out the Blue Driver OBDII. After a visual inspection of the intake system I noticed the intake house just after the MAF wasn't fully seated against the cuff and the clamp was a little loose. Airbox was also filthy so I cleaned it, put in a new filter, cleaned the MAF sensor, tightened the intake hose properly and the coff went away.

Mind you, in my initial research I found that this code can have simple solutions like mine, but it can also lead to months of finding out the cause by replacing damn near everything in the intake system. We're talking throttle body cleaning, intake manifold leaks, vacuum hoses, etc.

 

there are tricks and tools for uncovering intake leaks - for example spraying carb cleaner around seams, smoke test machines etc Pretty common on older cars - no so much on newer models. usually there's some common fail points - which is where the forum is really helpful. Mixture issues can also be caused by exhaust leaks as well.