New to the forum. Took my 2010 G37X to the dealer to have the reprogram done and it seems to have fixed the jerky downshifting and shift responsiveness issues but now I am seeing around 3 MPG less based on my daily highway commute. Can the TCM reprogram cause a decrease in MPG and if so, will resetting the ECU again help?

 

You're quitting over not getting a response within 24 hours? to answer your question, it COULD cause a slight decrease in MPG due to the way the transmission is behaving (holding gears, shifting, etc.) but I would imagine not as much as 3 mpg. Could be a combination of other factors, such as low tire pressure or driving habits.


You could try resetting the ECU and letting the transmission relearn your driving style.

 

Hey thanks for the response 93! Nah I was having a ****ty morning and vented it here! My tires were under about 3 lbs each and it's cold as **** here so I over inflated to about 34PSI and will see what that does to my MPG. Did notice that my tank wouldn't take the full load today when I went to fill it though so that was weird. It shut off at around 14.3 gallons and it was way empty so don't know why it didn't take the full 16 gallons?

 

Is that as estimated by the car, or as computed from miles divided by gallons and averaged over several tanks? The latter is far more accurate...

...except in your case.

 

I posted about loss of MPG after update a while back in my 2010.https://www.myg37.com/forums/g37-sed...ml#post3929802

I don't think i got much feedback either!!!

 

"Seemed?" I log my mileage religiously (in Fuelly as miles divided by gallons) and measured zero difference before and after the update.

 

IDK. i just look at the little MPG indicator. Maybe my wife was "flooring" my car everywhere. Dropping the Miles per gallon. My '13 does way better at 19.2. But, then again i don't let her drive it much after she wrecked my '10.

 

In my case, the indicated (estimated) MPG has never been consistent with the measured (calculated) MPG. YMMV (literally)

 

How far is it off?

 

I just posted the following in hopes of getting an answer to you quickly. If there isn't a way to access those values, then I will start recording them and get back to you in a few weeks. Please consider doing the same so we can compare notes in another thread to avoid hijacking this one.

 

Mine is at best 0.8 mpg off and at worse, more than 1.1 mpg off. I know our mpg is horrible, but, not to have an accurate mpg gauge is crazy.

Does anyone know how to adjust our computer mpg to a true reading?

 

Speaking of gas mileage, does anyone know if it's bad for the G37 auto transmission to be shifted into neutral when rolling? As us auto-tranny drivers know, the 7AT really drags the speed down when the foot is taken off the gas. I can roll a LOT farther without giving the car gas if I shift to neutral.

I seem to recall that rolling in neutral with the 7AT was not recommended but I can't recall the truth of that.

 

it's bad to put your car out of gear on any automatic transmission regardless of what car you have

 

I've read through and searched for updates on the 7AT and for the sake of saving me from reading 165+ pages...

Is the latest update ITB12-027D? This encompasses all 2011 and 2012 models? My car is a 2012 G37x with 33,500 give or take. Is there a way to check the VIN to see if I've already received the update?

Also, when I called the service department of two dealerships they quoted me $100-140 for the service charge to just look at it since my basic coverage is up. Is this right? Been a while since I've brought a car to the dealership (08) but they're charging for TSB / Service bulletins now??

A friend of mine works at AAM and has put me in contact with his friend who performs UpRev tunes. Since I'll be getting it tuned soon, is this something I will even need to look into and worth the headache of a dealership or will the tune fix any AT gremlins?

 

It should be covered under the powertrain warranty. But, according to the PDF below. Unless you have a convertible it doesn't apply to 2012 coupes and sedans.

http://www.infinitig37.com/TSB/ITB12-027d.pdf