Car is a 94 E320 with a little over 100k, with ASR. I'm getting a stumble at idle, ASR light on, fault code 10, or "Voltage at Air Mass Sensor too high or low". Are they serious about this being a voltage problem or is this just the sensitive way of telling me that I'm going to need a new Air Mass Sensor?

It looks like a had two problems going on here simultaneously - and that the ASR light had nothing to do with the code 10. The clue here was that the check engine light came on eventually too. I took off the wheel speed sensors, cleaned them (they were filthy), and have not had the ASR light again. I suspect dirty wheel speed sensors are responsible for more ASR lights than people realize.

So I'm guessing the code 10 went with the check engine light. I built the code reader, pulled a bunch of old codes, cleared them, drove the car again, and got a code 10 again (voltage at air mass sensor) on the built-in LED (DM), and a code 4 (hot film air mass sensor) from PIN 8. The car runs OK still except for some slight variation in the idle RPM on occasion. So is this all I need to know to go buy a new air mass sensor? Or is there something else it could be? I wouldn't even ask except that the air mass sensors are quite pricey.