Let's see, you bought a year and a half old car with only 3000 miles
on it, which would be extremely low, the averages are 12K to 15K a
year.

 First off, it's a Diesel, so it's a very safe guess that we are not
talking USA here - Probably Canada, or Mainland Elsewhere.  ;-)

 Did you get an exceptional price on it?  Do you know any of the
service history, can you trace down and talk to the previous owner?
The licensing agency should be able to do a title search and tell you
who the previous registered owner was.

 Because the first thing that pops into my head is that the car has
been trouble before, and the previous owner either returned it under
"Lemon Laws" or otherwise got out of the deal, or worse sold it back
at a big loss.

 Now the dealer sold the car to you without saying a word about any
prior problems.  And of course, the problems are starting almost
immediately.

 Also possible that the car was in a flood, driven into a lake,
swamped by flood tide of a storm or hurricane, etc.  Even if they
cleaned out all the water and mud and dried it out, being underwater
still does a number on the entire electrical system and serious (and
very expensive) problems will pop up for years.

 You need to start digging as to what's /really/ going on.

 Due to Hurricane Katrina and other serious storms, the US Insurance
Companies set up a Flood Vehicle Database of car VIN numbers that were
totaled by storms, in case someone tried to buy the cars out of a
scrapyard and clean them (and their titles) up for resale.
https://www.nicb.org/cps/rde/xchg/SID-4031FE9A-A8FA4374/nicb/hs.xsl/79.htm

 There may be similar services where you are.

      --<< Bruce >>--