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The PCM in the FEH has what's called "Keep Alive Memory" (KAM) and I would think most other vehicles have the same thing. KAM is a memory integrated circuit chip just like RAM in our computers. When the vehicle is shutdown, the 12V battery still provides a small amount of current to keep information stored so the PCM can access it again. When the 12V battery ground is disconnected for more than a few minutes, this memory is lost. This means you loose things like long term fuel trim which can screw up closed loop air/fuel ratio control.

Well, I'm here to tell you my KAM was lost when my FEH was being repaired and I've lost on average 5mpg. Ethanol does the same thing by changing my long term fuel trim. With the new SG11 firmware changes, we may be able to start viewing the LONGFT1 PID at different RPM/load point corrections. What do you think Carl?

Mark Smith enlighten us on GH about how to keep your settings with a small 9V battery, so I thought the information should be posted here also. A few of us purchased a settings keeper and it seems the price ranges from $5 - $15. I got mine at Super Walmart for $4.95 and it is made by Noco, part No. BTE296. Mark said you must plug it in a lighter plug that stays on when the key is off. The Noco unit comes with a 9V battery, so it's a good deal.

One thing that comes to mind about good FE and long term fuel trim was the MPG Challenge at Hybridfest. Debbie Katz provided me with her FEH which had great long term fuel trim maps. If I had driven a new FEH with the maps set at the default settings, my mileage would have most likely suffered.

GaryG

Gary, so the KAM is how our FEH's learn how we drive while we learn how to drive our FEH's?

Yes, the long term fuel trim is easily monitored with the xgauge feature of the scangauge. In fact, there are two different ways to monitor it. A one byte legislated PID 0x0007 or a two byte Ford PID 0x1156. I monitored this before and after the traction battery recall work and did not notice any difference. My LFT varies from -1% to about -9% depending on load and RPM. I assume if KAM is lost all points would go back to 0.

BTW, my mileage has dropped noticeably since the recall work. It appears to me the initial charging current at low SoC has been increased, while charging current at higher SoC levels has decreased. Again, this is just what it seems like to me, but maybe it is just a tropical delusion....

I think y'all are confusing KAM fuel maps versus STFT/LTFT.
The fuel *trims* update over a relatively short time, even
the "longterm" one -- on the order of a minute. The base
maps, on the other hand, tend to start at default values
and then get tweaked as needed by looking at longer-term
trends in LTFT. But with a varied bit of driving, even
those should get mostly updated within a day or so -- at
least in most ECUs as I understand it. If someone's got
good references for overall strategies across different
vehicles, I wouldn't mind reading up a little more.
.
_H*

Hobbit is correct you are confussing KAM with LTFT. When my PCM took a dive It took almost 2 tanks to get the milage back up.

BTW, my mileage has dropped noticeably since the recall work. It appears to me the initial charging current at low SoC has been increased, while charging current at higher SoC levels has decreased. Again, this is just what it seems like to me, but maybe it is just a tropical delusion....

I have also noticed my FEH charges much harder when the SOC is below 46%.

My pcm was so bad they could not retrive the original programing, I think I got the 08 programing when they reflashed because I noticed the ICE start was much softer when I got it back, which is one of the "fixes" in the 08 software.

All cars have some form of a KAM, my experiance is Fords take a little longer to "relearn", Fords also are harder to clear the KAM ( yes they can learn bad things)as you would have to have the battery disconected for 5 min or more. Some cars its gone in 10 sec.

Gary, so the KAM is how our FEH's learn how we drive while we learn how to drive our FEH's?

Sorry, for some reason this thread didn't show up as new post, so I didn't know anyone responded to it or I would have answered your question.

Right Debbie, your vehicle had great memories in KAM because of how you drive. I took advantage of that in the MPG Challenge. It has been over 700 miles since my KAM was reset to the default settings, and I'm not even close to the mileage I was getting before the reset.

This may be the reason there is such a drop in mileage in cold weather for you snow birds. If there is a change in winter gas, this would also effect LTFT.

This also may explain why I get great mileage all year round here in S. FL. I've only got ethanol 3 times and my weather never gets cold more than a few days at a time a few times during winter. It has taken on average 3 tanks to get back to normal after adding 10% ethanol to my tank.

Carl, I'm ready to bite the bullet on a new Xgauge, so are we getting a discount? Anyone?

GaryG