OK, B1231 is the engine coolant temperature sensor. That would make sense given that real-time value #6 reads -40. If that sensor is bad, I would expect that your aux fans would come on at high speed every time you turn on the ignition. Can you tell us whether or not they do?

__________________
"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles