Reprogramming a TCM?
 

Does anyone know what is involved in reprogramming a transmission control module (TCM)?

I have a 2009 Aveo, practically new with 2000 miles, and from what I've read it is shifting into 4th gear much later than it should, at around 45 mph. Consequently, it has a negative effect on gas mileage. The tranny is the Aisin 81-40LE.

Hi Thymeclock,

Welcome to the Chevy Forums.

Have it adjusted by a Certified Tech. I see many bad things about TM going to hell after people start doing adjustments themselves.

You may just need a physical band adjustment. You really want to get this done by somebody you can return to, who can be held responsible for any following problems.

Save money on something else, like a tuneup.

The car is practically new with less than 2000 miles on it. I have no intention of doing anything to it myself, as it is under warranty. But I would like to gain the knowledge of how it is done.

From reading the Aisin service manual for that transmission it verifies that it's going into fourth gear later than it should. If I take it to a dealer I expect the usual runaround or denial routine. I expect to be told "they are all that way", which may actually be true if the modules were not programmed correctly. If so, they probably won't want to do anything about it.

You could always just go to the sales department at the dealer, test drive a new one, and see how that vehicle shifts.

I know that - but even if they all exhibit the same characteristic, that doesn't mean the control module is programmed correctly. So ultimately that won't prove what it should be. The graph of shift points in the Aisin manual tells what they should be. According to the data, mine is shifting into high late, and I suspect others are too.

I've read numerous complaints of many Aveo owners who are disappointed with their FE, especially in city driving. These cars were originally estimated by the EPA as 27 MPG city. Then they revised it downward to 25 MPG. The best I have been able to do is 22 MPG with a very conservative driving style. Others have reported even lower FE.

The bottom line is that since it doesn't go into 4th gear until 45 mph the car will spend most of it's time in the lower gears, no matter how it is driven (unless the driving is exclusively highway at speeds of over 45).

Apparently it isn't the transmission itself that's causing it - it's how it is programmed.

I can promise you, unless you spend 99% of your driving at 43mph the late shift is not where your loosing the 5mpg your thinking your down. Realistically the estimated fuel economy figures are never accurate... my 99 volvo v70xc came with the window sticker when I got it, i believe it said 22mpg freeway +/-. I always kept the vehicle maintained, only quality supreme fuel (its turbocharged) and the best fuel economy I EVER got was like 19mpg and we regularly took it on trips via the freeway. Also keep in mind dependant on where you live that winter fuels are used and you will notice a decrease in fuel economy and sometimes other drivability concerns.

All I ask is that you understand its not the techs whom write this software. If its a problem I can assure you chevrolet is working on it, where I work we regularly get customers whom cruise the forums and when a problem is mentioned by others it instantly justifies you declairing all out war on your local chevy dealers service department. Bringing the car in OVER AND OVER will do NOTHING but put the poor tech in the middle of your "problem". The techs dont have a magic wand, so you comming in and pestering them with a problem they cannot fix means they are not getting paid to drive your car and verify it might be a slightly late shift but he cannot do anything about it. When a software update comes out, sure have it updated. All I ask is that you have a little respect for the poor tech your putting in the middle of this.

Again, I can assure you if your think a transmission software update is going to give you 5mpg, your slightly loony. I say this only because when and if chevy comes out with an update I have a feeling you will be very dissapointed.

The point is if the car you test drive shifts normally, they can no longer claim they all shift as yours does.

Actually, a good portion, if not most of the driving IS being done between 25 and 45 MPH. Most cars go into high gear at just under 40. This one stays in 3rd for the entire time between 25 and 45. It doesn't harm the car or the transmission any - just the FE. And the specifications of the manufacturer of the transmission show that it should upshift sooner.

I didn't say they did, did I?

So tell us, who did write the programming?

You sound very defensive. I haven't even brought the car to a dealer yet, let alone bring it "in OVER AND OVER". If they end up telling me nothing can be done I will pursue resolution on a different level. But in light of it being not within specifications and that it is staying in 3rd gear for a span of 20 MPH before upshifting, I do expect the problem to be addressed, not denied or ignored.

If you had read and understood what I wrote you wouldn't be calling me "loony". Maybe the fact that you also label yourself "stupid" illustrates your propensity for name-calling.

I came here asking what is involved in re-programming it. If you can't answer the question, fine - but extraneous arguments are not what I am seeking.

I apologize for coming across argumentative, I didnt mean to... I sincearly apologize.

Its not you and I (again) apologize if I came across this way, but like I said, I work in a dealership and deal with customers complaining about non existant problems absolutely denying that it "works as designed" for example the newer jeep grand cherokees with the 5.7l hemi engine, it has MDS (multiple displacement) where it de-activates cylinders in "economy" mode (idle or cruise), one customer in specific brought his car in multiple times taking hours of our best techs time in datalogging, and speaking with tech support because it didnt go into eco mode as glassy smooth as he wanted it too and the light in the cluster constantly comes on and off.

in that situation there was no fix, unfourtunatly to take a gas guzzler and make it get a couple mpg better there are SLIGHT downsides (to some people).

All I was saying was from a techs point of view it is AWESOME that you know your car so well (hell the toyota drivers cannot even get their trans into neutral and you know the name and the fact that its shift is delayed). I was offering advice as some people (obviously UNLIKE yourself) whom dont have respect for the fact its the tech working for free to diagnose the motherships design flaw.

I appreciate your respect, that is ALL I was trying to say.

(btw loony? come on man, there are a dozen other words that would have come up as **** if i ACTUALLY was trying to insult your intelligence, but i apologize for that too if it offended you).

Apologies accepted.

Actually I do respect techs, as I am one myself (but not in the automotive trade).

But to return to the issue at hand, there is a reason why the Aveo gets such inadequate fuel economy in city driving, and the very delayed upshift into high gear would account for it.

My asking who wrote the program for the TCM is not a rhetorical question. Obviously it was the transmission manufacturer (Aisin) that wrote the specs calling for lower shift points that I am experiencing. Chevy did not design or manufacture the transaxle. If it was Chevy engineering that programmed the TCM, it needs to be addressed.

What I am asking is can the TCM be custom reprogrammed by a dealer or is the programming a fixed package, incapable of being changed?