I can't find this exact issue anywhere.
'92 SC400, bone stock, high mileage ( 422,000 km), daily driver.
I changed both upstream oxygen sensors in the last 5k, but have a recurring code 25 which has popped up several times under the same circumstances - prolonged 100 - 140 kph driving, followed by a stop, such as for lunch, during which time the engine cools off, and then the code pops up when I resume driving and it goes through a specific temperature range. It never overheats, and the lights go off shortly after normal operating temperature is reached.
Any ideas?
Thanks