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Date: 27 May 2004 18:22:16 GMT
From: Dave Hinz <>
Subject: Re: Air Mass Meter Question

On Thu, 27 May 2004 18:08:11 GMT, Mark <> wrote: > Howdy, I have a 1991 Saab 900S and I think something is a little funny > with the air mass meter. I am hoping to get some advice. Mark, you've written perhaps the most descriptive and comprehensive description of a problem that I've seen in a long time. I'm guessing you do something heavy-duty technical for a living, for some reason. > The check engine light comes on for about a second or two > periodically. Sometimes this is accompanied by the engine stumbling > for a split second, sometimes not. I checked the check engine codes > and the first one is 12231 (no rpm signal) which is normal, since the > engine is off. The next code is 12221 (no signal from air mass > meter), Could it also mean "signal out of expected range", like it's out of tolerance, or is it only "no signal" which would indicate a disconnect? > So I followed Bentley's instructions for checking the air mass meter. > I unhooked it from the air filter, ran the engine above 2500 rpm and > then shut it off and watched the wire glow red for a second (burn > off). According to the manual this means that the air mass system is > probably working fine. Well, that means that the filament is intact. There's more to it than that, though; the temperature sensor, the feedback circuitry needed to keep the temp of the wire constant as the mass of the air cooling it changes the temp, ... that tells you the filament is OK but not the rest of it. > Does anyone have any suggestions or experience with this problem? I > hate to put a new part in there if it isn't the problem (the meter is > very expensive). I should say that I got a new air mass meter at > 118k. It only lasted until 132k and was replaced under warranty. I'm > now at 180k. Is 50k the expected life of this part? Is it sensible > for the failure to be so intermitent and short lived? I'm wondering if you have some sort of cabling issue that is causing this to fail, or causing it to _appear to fail_. Have you polished the contacts on the AMM and on the harness? I remember somewhere seeing a resistance figure between two pins on the harness to see if it's in range, but (a) that was for an '88, and (b) of course, I can't google it up right now for some reason. Dave Hinz

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