Bad gas mileage for no reason? Try resetting your ECU!

Over the past 4 months or so my truck’s gas mileage has been becoming increasingly bad. I thought it was due to the mods I did, like a lift, winch and slimline bumper, and Leitner bed rack so I just dealt with it. It started at around 18 combined, then went down to 15. Finally, at 13.5mpg on the regular, even when hypermiling, I had enough; I had to do something. I did a bunch of research and thought maybe it was something like worn spark plugs or the diff oil needed changing or something like that. The truck only has 27k miles on it so I thought I’d start with something simple. I disconnected the negative terminal and let it sit for a half an hour or so to allow the ECU to reset. Lo and behold, I started getting 19.5mpg regularly! Hope this helps someone.

 

Disconnecting the battery does not reset ECU's anymore, it does reset the throttle zero position which will eventually revert to its learned status.

Fuel trim is determined by the ecu and will again revert quickly even if the battery did reset the trim.

You are encouraging a placebo.

 

over what distances, that's an impressive improvement

 

Around 300 miles. Mix of offroad, highway, and surface streets. Plenty of hills, too! I drove from Carlsbad, CA to Anza-Borrego, did some off-roading and camping, and drove back and still had over a quarter tank of gas left. Dash said average mpg for the tank was 19.5mpg. I’m pretty stoked. I’ll update over the next few tanks.

 

Placebo or not, I’ll take the increased gas mileage. All I know is before I was getting around 13.5mpg tank after tank and that was with babying the throttle and keeping it 2k or under. On the freeway, it wouldn’t even shift into 6th gear half the time. Now, it’s 19.5mpg and goes into 6th gear and holds. Whatever disconnecting the battery resets definitely helped.

 

Are you even sure its true mileage? You may have confused the onboard computer for fuel economy by disrupting it.

 

The truck gets decent milage but each trip has to be 30 miles of highway. If its city driving stop and go a lot your gonna get 13.5 combined.

 

Yes, because I filled up completely after the “reset”, went on my trip, and filled up when I got back. I calculated it to be 19.2 actual. Still not bad. When I was getting 13.5, I did the same manual calculation and got around 14 so the dash is pretty accurate.

 

I drove to Phoenix and back for Christmas and got 15mpg highway. I was going 65 the whole time trying to save gas. Still didn’t help.

 

Were you loaded more than you were for anza??

 

Yeah could’ve been it. I did have a dirt bike in the bed and my wife with me. But the bike weighs about the same as all my camping gear and offroad equipment, plus the route is a flat straight line at a constant speed so I’d think that an Anza trip would get less mileage.

 

Did you go out the 10 or the 40 to Phoenix?

 

8 to 84 to 347 up to Gilbert.

 

Ahh ok. 10 is pretty much flat.
From what I know of the 8 is it's not very flat.
And 84 and 347 I am not sure about.
The slightest headwind also kills the milage.

 

Does anyone know how to actually reset your ECU?

 

Techsteam, a computer application. It also requires a certain cable. Search for it here, for a copy of the program. To actually reset the ecu, will not improve your mpg.

 

https://www.tacomaworld.com/threads/techstream-tips-and-tricks.597998/#post-20069509

Still need a compatible cable and a Bluetooth OBDII reader will not work. You can probably find a cable packaged with a very short subscription/trial version of techstream on Amazon and eBay, but most people have been using less than legit copies because it's dealer oriented software so they charge out the butt on subscription fees. The cable that comes with the Amazon and eBay versions is not the traxit cable you will see talked about here. That specific cable is used with a completly diffrent product called OVTune.

 

Also note that after using techstream to reset the ECU or TCU the vehicle has a very specific idle relearning process and it will take about 300 miles before the vehicle begins to settle into a smooth/predictable ride.

 

If it's going into 6th now and wouldn't before, perhaps it reset the transmission adaptive tables

 

I drive 80 miles a day total to work and back. Can confirm. Get 22-23mpgs regularly.