About 2 weeks ago I got a message on my dash saying "service 4wd" on my 2012 lancer ralliart. A bunch of looking around online got me worried it was the ACD pump as that's a common issue on these vehicles. Thought it would be unlikely because their failure is usually linked to corrosion due to being behind the rear wheels however this pump was replaced just a few years ago and relocated to the trunk where it's protected (while in possession of previous owner). Pump looks like it's in perfect condition, no visible leaks, and it's got a full fluid reservoir, however upon checking some codes getting both the C161e and 161f which I see is pump failure. Before looking into any rebuild kits is there any other testing I can do to figure out why exactly the pumps unresponsive to ensure I'm not spending any more money than necessary? Still new to all this so any help is super appreciated!