Hey! I had a similar issue with my 2015 Toyota Land Cruiser. I'd say my car expertise is at a moderate level. When I took my car to the workshop, turns out, it was a Damage to the wiring harness rather than the coolant thermostat. It cost me about €110 to get it fixed. Can you tell us more about your car's info, like its mileage and maintenance history? It could help us pinpoint the issue better. Cheers!

Hey, appreciate the response. Hmm, interesting. Wiring harness damage, that's something to consider. My Sequoia's racked up about 158741 KM so far, got it serviced pretty recently actually. Aside from regular oil changes and a brake pad change around the 150k mark, I've not had any major fixes done. Hope this helps!

Hey again! Thanks for getting back and sharing more details about your Sequoia. It certainly helps. Given the mileage and the good upkeep (kudos for that by the way), wiring harness damage might not be the prime suspect - though it's never completely off the table. However, overheating coupled with check engine light being on could still be syndromic of a faulty coolant thermostat, as you initially suspected. It could be stuck closed, hindering your engine's cooling system. Then again, it could also be a failing water pump or a clogged radiator. I say it's best to get it diagnosed in a trusted shop. If it turns out to be the coolant thermostat, the cost shouldn't be too steep - I had it changed in my Land Cruiser a couple of years back, set me back around €40 and some change for parts and labour in total. Keep us posted about what you find. Good luck!

Awesome, genuinely appreciate the comprehensive advice! I wholeheartedly agree, a trip down to a trusted workshop seems like the best step forward. I'll inquire about the thermostat, water pump and radiator while I'm there. It's reassuring that the costs might not be astronomical after all. Will indeed keep you all posted about the fix and the final verdict. Thanks once again, cheers!