Okay, someone let me know it this makes sense. Being a shadetree computer geek, it makes sense to me. Here's my little set of hypotheses; correct me if I'm wrong...

1. The engine management system works by gathering data from the sensors, drawing conclusions from that data and adjusting the state of tune of the car accordingly. If the sensors which submit that data are faulty, the system will try to interpret the data it has in order to make the car run as best it can. This would explain why a bad sensor will make the car run poorly.

2. If a car has a defect in a part for any period of time, it adapts based on faulty data. If that part is replaced, it may then misinterpret the data coming in due to the sudden change in the information it is being given.

3. Ergo: my having replaced my crank position sensor and/or fuel pressure regulator made a change in the information being given to the engine management system. For some reason, the system reinterpreted the data as meaning that my mass air mass meter and oxygen sensor were at fault (codes 1-2-1 and 2-1-2). Driving the car for a few miles alowed it to acclimate to it's new data flow. Resetting the system cleared the codes.

4. Hopefully, they won't come back.

So, does any of this make sense, or am I out of my tree? Or both?

-EdM.
Franklin, MA
'90 240DL Wagon "Lola"
'72 1800ES "Galadriel"