Seems to me the clue is the "when it reaches operating temperature" bit.

Check the resistance on the coolant sensor. My earlier M102 has a two in one sensor in the housing. You compare the resistances on the pins diagonally. Check the connections on the coolant sensor.

(It is a start if you can't get codes)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!