So last week, I had t disconnect the negative terminal of the battery to reset some dash board lights after the "you know what" mod.

After a week of driving and a tank of gas, my MPG dropped significantly after I disconnet and reconnect the battery.

I was averaging 21.5MPG before and last tank, which is my routine work commute everyday that I had been driving for the last 4 months, is only giving me 18MPG.

Are those two things related? Will disconnecting the negative terminal of the battery reset the ECU? And it will have to learn my driving style again? Any suggestions on how to get my MPG back or any other suggestion? Thank you in advance.

 

i found this very strange my self! but mine had the opposite affect, my MPG went waaayy up? haha I was barely able to hit 250 to a tank all city, this tank will be closer to 350? pretty confused myself

 

Yes, you reset the ECU, which controls the throttle input. Does your car feel more sensitive than before? This happens when the ECU is reset. The MPG will drop because it uses more gas on a more sensitive throttle. After a while, it will learn your driving habits again and you will get a normal MPG as before.

Don't worry about it. I reset my ECU all the time using the pedal method and my MPG always drops for a bit. However, I like the sensitive throttle better. The car will accelerate faster and there's less lag time between your foot and the engine response.

 

^+1 things will be back to normal in a few days as long as you maintain your old driving habits and dont try to abuse the increased sensitivity

 

I didn't like the sensitive throttle, I went to the dealership and did the sensitive throttle TSB.

Now to think of it, the pedal does feel a little stiff and I have to push in more to get the throttle response that I used to get about the TSB was done.

So every time I disconnect the battery, or replace battery, It reset the ECU. So if I want to have that smooth throttle again, I will have to go get that TSB done again after each time? It doesn't set into the ECU as a permanent change? I thought it was a TSB that you cant turn back around to....

I want my gas mileage and smooth ride back....

 

No, the ECU just wipes all memory of your past driving. It learns your driving habits and tries to make the most fuel efficient throttle response possible. You have to give it time to learn your driving habits again.

The TSB was there to flash the ECU. The ECU stores this program. You do not need to redo the TSB. It's like your computer. Once you flash the BIOS, you don't need to reflash everytime your hard drive is wiped clean when you reinstall Windows.

This happens to every vehicle. Once your battery is disconnected for longer than a couple hours (maybe minutes?) the ECU is reset. The Lexus ES350 I also own does this. Don't worry, your MPG will go back up and your ride will be smoother. It may take a couple hundred miles before it relearns your driving habits.

I personally reset mine every couple of weeks. I find that the throttle response becomes dull after my lead foot =)

 

Great, thanks for all the good info guys, hopefully there won't be traffic on the freeway for the rest of the week. It was all jammed up this morning on the freeway, and I was worrying the ECU is going to learn that's the way I drive.. in stop and go traffic. I feel like the G is an innocent new born, where I need to keep all these bad habit to the minimal so it wont develop into bigger problem.. like bad fuel economy.... haha

 

That is strange...

R u sure its not because of the HFC? That your gas mileage is down?

Could there have been something wrong on the install?

 

My car is stock..

 

my concern is similar,

i have the 07 sedan and i am going on vaca this coming friday till the end of the year. my father being the old skool he is recommends me that i disconnect the battery terminal. called the dealership, they said it is not necessary,

what is recommended?

 

What do you mean? Are you not driving the car for a month? You don't have to disconnect the battery.

If you do, your ECU will reset.

 

Yeah, there's a reason they call it 'old school' - it's because people don't do it that way anymore Leave the battery connected. If you disconnect, you'll lose all the radio presets and will likely trigger your TPMS sensor (tire pressure monitoring system), which is a pain in the *** to reset.

 

If you are leaving it for a month or a few weeks, get a trickle charger.

 

trickle charger? u mean a portable jump starter?

i am going on vaca for a month, it will be staying inside the garage...

 

Hey Mathnerd, what is the process of this pedal method you mentioned?

_Michael