Friend of mine had this on a '92 240 saloon recently. It turns out there is a main fuse on the inner wing, it corrodes and sends spurious signals to the ECU. It would run fine for awhile after the light was reset, few days later the light would come on again.

Furiously cleaned the fuse and the problem went away. Prior to that the previous owner had fitted a new AMM, oxygen sensor, temperature sensor, and gave up when the garage told them it needed an ECU.

Regards

You might check the air box thermostat. If it is putting hot air in all the time it can cause both lower gas milage and premature failure of the air mass meter. It is cheaper to replace than the air mass meter.

That mileage is a little low but not out of line. The manual trans cars

have a lower compression ratio than the automatics. Manual has 9.5 to

1 and autos are 10.2 to 1. So, they can get a little better mileage.

Try resetting the code and waiting to see if it comes back on. Make sure

the connector to the AMM is clean without any corrosion on the contacts.

You can use dielectric grease in the connector to prevent corrosion. My

mothers 90 has 223k mi and the computer is a pathological liar. It keeps

having the light come on and there is nothing wrong. The computer itself

is causing this so I just covered the light since it runs fine. Maybe I'll

get her a computer in the near future but in the mean time a little piece

of black electrical tape is just the thing.

Dave 82 242ti