eco reset resulting in higher mileage??
 

battery went out on me and i replaced it. also right after that i had trouble with brake light switch staying on and corrected that too. battery was disconnected for 8 hours straight then drove home and disconnected again for 3 hours till evening. ever since then i have been seeing better readings on my scanguage.

also finaly took a trip that got engine heated up and that was realy impressing me with the numbers i was getting at steady speeds. usualy i only see water temps in mid 180's well i was seeing 200-205 at speed. i was staying at 5 under the limit of 45-55 mph.

*title should read E.C.U Reset

HMMMM i wonder why?

I recently replaced my O2 sensor. It was recommended here at gassavers, that I disconnect the battery to reset my ECU, so it could 'learn' the new sensor. That made sense to me, since I knew the ECU had to average the signal from the sensor. After reconnecting the battery, the fuel GPH was all over the place for several days. And it took two weeks for it to settle down completely. I found my idle GPH was down from 0.4 to 0.3. and I could see a 0.4 GPH decrease on the highway too.

I attributed this gain to the O2 sensor. But perhaps you've stumbled onto something else. Maybe the ECU needs to relearn an older sensor, as its signal has changed. Wouldn't that be funny if Bosch lost half the sensor market because people stopped replacing their sensors, and just reset their ecu. :D

Seriously, it would be nice if some more folks would reset their ECUs so we can give this a good test.

A failing battery will play havoc with the electrical system, and can take a long time to show up. It can also drag the alternator down. Replacing with a new battery may be the fix because the alternator won't have to work as hard and the computer will be getting a constant voltage.

NOTE: If the alternator fails in the next week, replace both the battery and alternator at the same time. My standard procedure is to replace both together, after a nasty incident I had where I replaced 4 batteries and 3 alternators. Turns out that the problem was I had a bad battery, and the alternator cooked itself trying to keep it charged. When I replaced the alternator, the battery had drained too far, which then cooked the new alternator, which didn't show itself until after I had to replace the battery, ect. It was a vicious cycle that didn't resolve itself until I replaced both together. Once I did that, I had no further occurrences. Luckily for the replacements were all warranty issues, but that was still a lot of useless work. Now this won't necessarily happen every time as I've had batteries and alternators fail in the past without taking the other one along, but I'll not go through that again.

Good point there Telco!

A failing battery can also reduce you FE numbers and also tend to "boil" water out the caps.
I check my cars battery with an old analog battery charger ever time I do an oil change. What I'm looking for is how fast the battery amp draw drops off and at the same time how quickly the battery comes up to the normal regulated voltage for the specific car.
On my 4Runner thats about 14.3vdc. I expect the battery to come up to voltage in about a minute or two and watch it with a DVM. If it don't it may be sulfated and need some long and slow charging to help that or its just going bad. Weak battery's may sit for hours on end drawing 3-4 amps and never come up to the proper voltage and that hurts your FE and "boil's" out the water at the same time.
My new favorite battery is the AGM type since they take a charge very quickly, tolerate getting cycled and never boil. Thats why I'm running an Optima battery.

I don't know. Just have to see when i refuel if they are for real or maybe the settings changed somehow when battery was disconnected.

I think i might get a new battery soon so ill test it then.

my shop manual recomends removing the fuse that resets the ECU, or removing the battery cable while doing almost any work on the engine or sensors, I don't do it as often as I should, but it seems reasonable.
I think a number of more sensitive sensors run off 5 volts, and have a low voltage power suply to step it down for them so the sensor can be more acurite, it's also easier for the computer to be standarized.

I'm thinking maybe old battery was was causing alternator to work more to recharge.

Hmmm. So, if everyone thinks LxMike's increased FE was due to replacing the faulty battery, not from reseting the ECU, then I guess I'll have to attribute my FE increase to the new O2 sensor.

I'd still like to see some data from folks resetting their ECU's though, just to see if there is any effect.

No luck!
refueled today and mileage was in same range as before. guess when i disconnected battery it somehow reset the scanguage adjustment and now that i refueled it's all messed up. i set for what i pumped and reading was way outa whack. checked the adjustment when i got home and it was showing -56%!! wtf?? i'm almost ready to get rid of the thing.

Mike, are you ever going to stop adjusting your SG?? I will try to help again.

Clear your settings by (use default settings). Set your tank size to 12 gallons. Set your fuel type to (hybrid). Engine size to 2.0. Use the 1 extra click method to fill, and please use 1 extra click method for every fill thereafter. Changing your fillup method constantly confuses everything. Then go to fillup (push done) do not ever change settings, just push done. Make sure you have 0% adjustment. Do this for a couple tanks and you will have your SG stabilized.

When you make the adjustments you have been making, you are essentially telling your SG it is wrong and your filling methods and pump inconsistencies, tilt, and temps are always right. What would you expect it to do? You are telling it what to do and when it does that, you don't like that.

I know in my own experience SG has been very accurate in recording the amount of gas used. I believe the vast majority of lack of agreement between SG and gallons pumped is filling methods.

I use gallons pumped to keep records and I do not adjust SG at all, over a
period of time SG gallons used will become very close to actual.

Hope this helps. Again. CO ZX2

it got messed up when i put in new battery. i just changed all to original setting. 2.0 engine, 12 gal tank, 0 fuel ajustment and hybrid mode. i had it pretty close before the battery died on me.

Whoa.... I thought the only feedback the SG got was when the user completed the loop and physically entered how many gallons were actually used. Is there another feedback loop the SG uses automatically?

I'm going to do a reset and try the method you just outlined. I've been consistent with my fuel ups as the adjustment is typically no more than .2 gallons either way. I also round up to keep the SG on the conservative side of error :p

hmm i have the same engien and prolly the same PCM in my truck. i just replaced my o2 sensor maybe 3 months ago but never disconnected the battery. i also yanked the egr valve off and nevr disconnected the battery.
maybe i will try that later today...see what happens. i dont have a very good baseline mpg tho usually around 22-25 but since i yanked the egr off its been high 27's 28's.

One of the issues with my Civic was the ECU. I had it replaced once. But the car would get into a ,,, Im not going to do good mpg for you mode. I would reset the ECU and it would come right back up for a month or so.

Very strange. One of the many reasons it had to go.

A peek inside my ecu shows a few things that might help FE when it's reset. Or it might not. As usual, other cars may respond differently depending on their strategy.

Here's a list of the things that are remembered by the ecu and adjusted to account for different driving conditions
Octane. My car has a variable that is subtracted from the calculated ignition timing to make up for frequent or large ammounts of engine knock, i.e. bad gas. When knock is heard the octane value is slowly lowered from 100%. Naturally the ignition timing is pulled immediately, too. When the octane value is less than 100% it pulls timing all the time to prevent knock. If you're not getting knock, then resetting the ecu will bring the octane value back to 100%. If you are getting knock, resetting the ecu will give you more knock until the ecu can readjust. If the motor is old and knocks from loose parts, the ecu might read this noise as real knock and pull timing+octane. In this case resetting the ecu will help briefly.

Fuel trims. Personally I prefer that these don't get reset since they help the ecu add the right ammount of fuel instead of guessing wildly. IIRC all OBD I and II cars have fuel trims.

Idle speed control motor position.
And of course all the error codes will go away until next time.
OBD II will initialize it's smog test readiness cycle again.

Once you get it stable again, when you fillup after running a full tank thru it, note the % of fuel adjustment. You will need to reset that or consumption and mpg numbers will be way off. Mine is at over %12 on the saturn.

Also, you need to reset your mileage adjustment, so make sure to write it down. This adjusts for the difference between how far the car thinks it went vs real distance checked via GPS or mile markers. Most cars are off by at least 1/2% from the factory.

I hit these same problems each time I move the scangage from one car to another. Writing down the settings and putting them back in the same is the solution.