The check engine light on my '97 C230 w/75k mi has come on, the engine seems to be running lean. My scanner pulled trouble code P0170, "Fuel Trim Malfunction." I have read in other posts that this is usually a result of the MAS. Data from the MAS was in real-time mode so I believe it is OK but wouldn't know otherwise. However, the data from my O2 sensors looks like #2 may be bad. #1 O2 ran at about 0.1 volts. Once the #2 warmed up it ran at about 0.8 volts. What is the nominal operating voltage of the O2 sensors? None of these sensors have ever been replaced. Thanks...