WOW! great write-up

I would still want to monitor heater voltage OR better yet, monitor O2 sensor current draw. Make sure that the heater is getting & using the correct amperage.

Also try setting the base duty cycle at 75-80% and see what happens.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator