My car randomly threw this code as well. I have a 92 190E with m103 motor - California car as well. Nothing seemingly wrong with it and it just threw the code while accelerating somewhere. No change at all in the way the car drove, idled, etc.

I cleared it to see if I could replicate it and observe what conditions it was, but no luck. It's been 1k+ miles since I got the code and I can't replicate it now. Let me know if you find anything and I'll try the same on my car.