Infiniti EX Overheating: Thermostat Issue or Something Else?

Hi there! I've got some experience working on cars , and I had a similar issue with my 2012 Infiniti FX diesel. The symptoms were exactly the same overheating and check engine light. Initially thought it was the thermostat too, but when I took it to my trusted workshop, they found damage to the wiring harness that was affecting the cooling system sensors. Cost me around 110€ to fix, and it's been running perfectly since then. Could you share more details about when this started happening? Like, does it overheat immediately after starting or after driving for a while? Also, have you noticed any coolant leaks? This info would help me understand if you're dealing with the same problem I had. By the way, how many miles/km does your EX have? That could be relevant too. Good luck!

Thanks for sharing your experience! Mine started overheating about a week ago, usually after driving for about 15-20 minutes. I'm at 159187 KM and just had my service last month. Haven't noticed any coolant leaks, but I'll definitely check the wiring harness too that's a good tip! Did your mechanic mention any other potential causes I should look out for?

Hey again! Yeah, definitely those symptoms do sound pretty similar to what I experienced. In my case, the mechanic also mentioned a couple other things to watch out for. After the wiring harness issue, they actually found that my water pump was showing early signs of wear too, though it wasn't the main problem at the time. Since your mileage is pretty close to what mine was when I had these issues (I was at around 165000 KM), it might be worth having them check that as well. One thing I forgot to mention in my first reply before I got it fixed, I noticed the temperature would fluctuate a bit on the gauge, especially during city driving. Did you notice anything like that? My mechanic said this was actually a pretty good indicator that it wasn't just a thermostat issue. By the way, since you mentioned having a service last month, did they do a pressure test on the cooling system? If not, might be worth getting one done it's usually pretty cheap and can help pinpoint where the problem is. Keep me posted on what you find out! These Infinitis are great cars once you sort out these little quirks.

Thanks so much for all this detailed info! Actually, now that you mention it, I have noticed the temperature gauge fluctuating during city driving that's really interesting about it being a sign of something other than the thermostat. They didn't do a pressure test during my last service, so I'll definitely get that done. I've called my mechanic and scheduled an appointment for tomorrow morning. I'll have them check everything you mentioned the wiring harness, water pump, and get that pressure test done. It's really helpful knowing what to ask them to look for, especially since our cars are so similar in age and mileage. I'll update the thread once I find out what's actually causing the problem. Really appreciate you taking the time to share your experience it's definitely given me a better idea of what I'm dealing with!