I have been battling the Check Engine Light (CEL) and the 221 and 231 codes on my 1995 940 with EGR for quite a while. I won’t burden you with all the details and history right now, but I did go to the junkyard today and I bought another 016 Air Mass Meter (AMM). I found two of them at the junkyard. One was from a 240 and one was from a 740 turbo.

The one from the 240 had a bunch of old oily water sitting in it, so it did not look too appetizing. The one from the 740 turbo was sitting high and dry, so it looked better. Both were the 016 editions of AMM.

But, they were not constructed the same. If sighting through the barrel, one of them had a part in the center that looked like a fork with a heavy light bulb filament spanning the fork.

The other one just had a vertical blade thing in it instead of the fork and filament. The blade was constructed of a strip of metal that extended about a half inch into the bore, it was about 0.020 thousands of an inch thick, and it was about 3/16 of an inch wide. The 0.020 thousands dimension faced the airflow.

I bought the one with the blade rather than the oily one with the fork and filament. But, the on one my car has the fork and filament. My thought was that Bosch made a manufacturing modification at sometime, and that they should be functionally the same since they have the same part number. The preamble numbers in front of the 016 are also the same between the two styles. There are some other numbers on one of them that are not on the other. I can go read them if it is an issue.

So, does anybody know about this difference? If they are functionally the same, does anybody know which is the newer style? Also, is the tiny wire the sensor, and is the fork/filament (or blade) the clean-off heater? Or, is it the other way around?

The new one is on the car now, but I haven’t done the 50 – 150 miles required yet to see if the CEL code comes back.

Thanks to Art Benstein for the tip in the FAQs about using a tire pressure gauge to check the fuel rail pressure. I would have done it like that anyway, but it was nice to know that I was following a proven path (except that I just did it with the engine running, which was not recommended for safety reasons). I ran the test before going to the junkyard since fuel pressure can set the same codes.

Thanks,
Charley