1996 E300 - sub-zero "check engine electronics"
 

Hey folks - I have put 32K on my E300d since August 1, 2010. A great ride, and I really enjoy seeing 34-35mpg on long hauls. One strange occurrence has been popping up over the winter - if the temp outside drops below say -10 to -15, I get a "check engine electronics" warning. The only symptom is that I get a harder shift (suggesting a possbile vacuum issue) as well as no floor heat, which is kind of bizarre. If the temps remain at sub-zs, then the warning stays. Once it returns to say 20 above or better, the warning goes away on it's own after a few starts... Not a real problem for me, but I prefer to understand exactly what is going on, and to address the issue if possible. Any thoughts are greatly appreciated!
I plug it in to keep the juices warm, and it has always been an excellent starter, regardless of the temps. I add a dose of additive to each tankful, and run (presumably winterized) straight #2 diesel...
Cheers

It would be interesting to see what a code reader would come up with when those errors appear. I live in Jersey, and thank God we haven't gotten -10 to -15 degrees, but when the temperature goes below 20 degrees, my car starts to sound and act a little different. I have no shifting problems or error codes, but my vents are much slower to respond than usual, and my power steering is a little slow getting up to speed. I also have a Scanguage connected to the OBD port full time, and my selected color for the display is blue. Well, when the temps go below 20, I end up starting with green, then as the car warms up, yellow, and finally back to blue. My car is out in the cold full time, and I have never had a problem starting, but I take my time when first starting out to allow give it a little time to get things warmed up.

This just a SWAG but can the clamate control unit can trigger fault codes on the service indicator?

The first thing that jumped into my head is a component in the unit is failing at low temps or possibly a poor solder joint that's efffected by cold.