Likely bad ECT. My guess is that you have more than 150K... Best is to replace both the tstat + ECT. I found a way to replace both w/o removing the PS Pump. Here is a DIY for my 2006 XC90 2.5T. You should check FCPEuro for PN for your year. Stick to Wahler brand, about $100. https://www.matthewsvolv...