Through this whole thread no one has said what year and model were are discussing, but the EHA gives me some clues. I never heard the term" fixed operating mode. I'm guessing it would run rough cold because there would be no reduced control pressure like the basic KE which had a warmup compensator and also didn't use a temp sensor. It would be operating just like the KE system and have to be running lean when cold with the electronics dead. Now I'm curious enough to pull the EHA plug on one of my cars and see how it runs cold.
That constant 90% you are seeing is not a duty cycle. It is either saying you have a car with onboard testing system or you have a fault code stored and you will have to look it up in the code book. I don't have my books at home to look it up for you. Sorry.
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