Reprogramming a TCM?
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Joined: May 2008
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I have to agree with you, OP. If I purchased a vehicle with fuel economy as a primary objective, I would expect it to get at least the sticker mileage on economy runs. I would also be a little cranky about a new transmission so obviously hanging up in a gear the way you're describing.
Maybe just a call to your dealer's service department would shed some light on the matter. After all, the problem you're describing could be a number of things.
Maybe just a call to your dealer's service department would shed some light on the matter. After all, the problem you're describing could be a number of things.
Last edited by therewolf; Mar 15, 2010 at 4:44 PM.
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Joined: Dec 2009
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engineers come up with the software... dealers then have access to the updates to flash your trans controller.
The techs dont have the ability to go in and change code and modify shift points and such, they only have the ability to "flash" modules with software designed by guys sitting in an office with pocket protectors and thick glasses.
Yes take it in and make the complaint known, know for sure if it is a software thing.
Also, like I said, dependant on where your at winter fuels WILL cause a decrease in fuel milage. We regularly get complaints of decreased fuel economy in new cars over the winter. Mainly new cars simply because those are the ones that bring it to the dealer as the "repair" should be free and they havent had it long enough to see that change and realize it happens.
The techs dont have the ability to go in and change code and modify shift points and such, they only have the ability to "flash" modules with software designed by guys sitting in an office with pocket protectors and thick glasses.
Yes take it in and make the complaint known, know for sure if it is a software thing.
Also, like I said, dependant on where your at winter fuels WILL cause a decrease in fuel milage. We regularly get complaints of decreased fuel economy in new cars over the winter. Mainly new cars simply because those are the ones that bring it to the dealer as the "repair" should be free and they havent had it long enough to see that change and realize it happens.
Last edited by stupidnoob; Mar 16, 2010 at 3:33 PM.
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Joined: May 2010
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very true,
I do get very low FE on my aveo 1.4 notchback sedan (SE)
my wife bought in Jan this year (2010), it was manufactured in 2006 but only registered in Malaysia in 2008.
somehow darn chevy distributes only 1.4 sized engine in south east asia....well at least for Malaysia and Singapore...
it is really under powered in this region's version, no wonder not much sales in this region of the world. many prefered toyoto vios or honda city instead here due to their good FE in city driving. hell, even the local ****ty cars like perodua and proton have better FEs compared to my aveo...
I am only able to get like 8-9 km/L
which converts to 18.82mpg - 21.17mpg according to this url:
http://www.vangeyn.net/mpg/?km=9&submit=Convert
that is in city driving,
in highway a.k.a freeway doing at average speed of 120kmh
i get up to 12km/L
which converts to 28.23mpg
that is the best it can perform...
for a 1.4 / 1.6 engine car this is very low FE...
perhaps since it is korean made, it is kinda expected....
I do get very low FE on my aveo 1.4 notchback sedan (SE)
my wife bought in Jan this year (2010), it was manufactured in 2006 but only registered in Malaysia in 2008.
somehow darn chevy distributes only 1.4 sized engine in south east asia....well at least for Malaysia and Singapore...
it is really under powered in this region's version, no wonder not much sales in this region of the world. many prefered toyoto vios or honda city instead here due to their good FE in city driving. hell, even the local ****ty cars like perodua and proton have better FEs compared to my aveo...
I am only able to get like 8-9 km/L
which converts to 18.82mpg - 21.17mpg according to this url:
http://www.vangeyn.net/mpg/?km=9&submit=Convert
that is in city driving,
in highway a.k.a freeway doing at average speed of 120kmh
i get up to 12km/L
which converts to 28.23mpg
that is the best it can perform...
for a 1.4 / 1.6 engine car this is very low FE...
perhaps since it is korean made, it is kinda expected....
Last edited by raysky; May 20, 2010 at 10:15 AM.
Thread Starter
CF Beginner
Joined: Nov 2009
Posts: 13
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I have to agree with you, OP. If I purchased a vehicle with fuel economy as a primary objective, I would expect it to get at least the sticker mileage on economy runs. I would also be a little cranky about a new transmission so obviously hanging up in a gear the way you're describing.
Maybe just a call to your dealer's service department would shed some light on the matter. After all, the problem you're describing could be a number of things.
Maybe just a call to your dealer's service department would shed some light on the matter. After all, the problem you're describing could be a number of things.
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<!--[if !supportEmptyParas]--> <o></o>
The transmission is the Aisin 81-40LE, an ordinary 4-speed, with torque converter lockup. It is found on all Aveos made from 2004 to 2010. I recently obtained the Aisin service manual for this transaxle. There is a graph indicating the manufacturer’s specification for shift points. (The graph is stated in KMH, so I’ve converted the figures to MPH for this discussion.) The points vary slightly according to the throttle position (TPS) reading. On my car I have a scan gauge that reports the actual TPS reading. Slow acceleration is about 25 TPS; brisk acceleration is about 35 TPS.
According to the graph, at 25 TPS the shift points should be at about 11, 20 and 27 MPH. At 35 TPS it should shift at about 12, 22, and 32 MPH. Here is what I am actually getting on my car at about 30 TPS, which is moderate acceleration: it up-shifts at approximately 15, 25, 32 and the torque converter lockup does not occur until 45 MPH. In other words, all the shifts are delayed. Most 4-speed transmissions shift at approximately 10, 20 and 30 MPH and reach converter lockup by 40 MPH. This very delayed TC lockup, which does not occur before 45 MPH, accounts for the poor city fuel economy.
I live in suburbia. On major roads here the typical speed limit is 40. In traffic it is usually impossible to reach 45 – thus our Aveo is spending most of its time in the lower gears and the TC lockup is never actuated. If it were to lockup sooner it would yield much better fuel efficiency. Without engaging converter lockup there is no way this car will ever yield the estimated 25 MPG in city driving – no matter how it is driven.
<!--[if !supportEmptyParas]--> <o></o>
Transmission shift points are entirely determined by the transmission control module (TCM), which was designed and programmed by Chevrolet. The shift points with which it is programmed differ widely from the documented specifications of Aisin, the transaxle manufacturer. When I visited my Chevrolet dealer to ask if the TCM could be reprogrammed they told me that they could do nothing to change it, unless Chevrolet had issued a service bulletin for an updated program. This has not been done in the past five years that Chevy has been using this transmission in the Aveo. In other words, unless and until Chevy engineering rewrites the programming of the shift points and offers it as a software update for dealers to install, nothing will rectify this engineering deficiency. I then visited my local transmission shop (AAMCO) and asked the same questions. They confirmed that there is no way to reprogram the TCM unless Chevrolet rewrites the programming for it.
<!--[if !supportEmptyParas]--> <o></o>
From information I have obtained, this is a very common complaint for Aveos. Most owners are unaware that their cars are late in shifting, but are expressing frustration with their poor city MPG. Since the actual TCM programming is divergent from the documented specifications of Aisin, this amounts to a defect in that the car does not up-shift when it should. I intend to pursue this complaint with Chevrolet until it is resolved.
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Joined: May 2010
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Wow, u really do research a lot on this,
good luck with the complaint, do make sure they send the update world wide to Malaysia too! I want the updated reprogramed TCM too
by the way is TCM the same as ECU?
sigh....i guess it's better off to go for a manual car heh? given the fact that all these transmission control stuffs are getting programmed badly...
good luck with the complaint, do make sure they send the update world wide to Malaysia too! I want the updated reprogramed TCM too
by the way is TCM the same as ECU?
sigh....i guess it's better off to go for a manual car heh? given the fact that all these transmission control stuffs are getting programmed badly...
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I took the car to my local dealer. Diagnostic testing indicated a problem with the accelerator pedal assembly, which they replaced under warranty. Before the repair was done I could not feel the car shift into fourth gear at all; since the repair I can now feel it shift into fourth, but the poor fuel economy remains the same.
<!--[if !supportEmptyParas]--> <O></O>
The transmission is the Aisin 81-40LE, an ordinary 4-speed, with torque converter lockup. It is found on all Aveos made from 2004 to 2010. I recently obtained the Aisin service manual for this transaxle. There is a graph indicating the manufacturer’s specification for shift points. (The graph is stated in KMH, so I’ve converted the figures to MPH for this discussion.) The points vary slightly according to the throttle position (TPS) reading. On my car I have a scan gauge that reports the actual TPS reading. Slow acceleration is about 25 TPS; brisk acceleration is about 35 TPS.
According to the graph, at 25 TPS the shift points should be at about 11, 20 and 27 MPH. At 35 TPS it should shift at about 12, 22, and 32 MPH. Here is what I am actually getting on my car at about 30 TPS, which is moderate acceleration: it up-shifts at approximately 15, 25, 32 and the torque converter lockup does not occur until 45 MPH. In other words, all the shifts are delayed. Most 4-speed transmissions shift at approximately 10, 20 and 30 MPH and reach converter lockup by 40 MPH. This very delayed TC lockup, which does not occur before 45 MPH, accounts for the poor city fuel economy.
I live in suburbia. On major roads here the typical speed limit is 40. In traffic it is usually impossible to reach 45 – thus our Aveo is spending most of its time in the lower gears and the TC lockup is never actuated. If it were to lockup sooner it would yield much better fuel efficiency. Without engaging converter lockup there is no way this car will ever yield the estimated 25 MPG in city driving – no matter how it is driven.
<!--[if !supportEmptyParas]--> <O></O>
Transmission shift points are entirely determined by the transmission control module (TCM), which was designed and programmed by Chevrolet. The shift points with which it is programmed differ widely from the documented specifications of Aisin, the transaxle manufacturer. When I visited my Chevrolet dealer to ask if the TCM could be reprogrammed they told me that they could do nothing to change it, unless Chevrolet had issued a service bulletin for an updated program. This has not been done in the past five years that Chevy has been using this transmission in the Aveo. In other words, unless and until Chevy engineering rewrites the programming of the shift points and offers it as a software update for dealers to install, nothing will rectify this engineering deficiency. I then visited my local transmission shop (AAMCO) and asked the same questions. They confirmed that there is no way to reprogram the TCM unless Chevrolet rewrites the programming for it.
<!--[if !supportEmptyParas]--> <O></O>
From information I have obtained, this is a very common complaint for Aveos. Most owners are unaware that their cars are late in shifting, but are expressing frustration with their poor city MPG. Since the actual TCM programming is divergent from the documented specifications of Aisin, this amounts to a defect in that the car does not up-shift when it should. I intend to pursue this complaint with Chevrolet until it is resolved.
ate; margin-top:0in; margin-right:3.0in; margin-bottom:0in; margin-left:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan lines-together; mso-layout-grid-align:none; punctuation-wrap:simple; text-autospace:none; font-size:11.0pt; mso-bidi-font-size:10.0pt; font-family:Arial; mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman";} p.SignatureName, li.SignatureName, div.SignatureName {mso-style-name:"Signature Name"; mso-style-parent:Signature; mso-style-next:Normal; margin-top:48.0pt; margin-right:0in; margin-bottom:0in; margin-left:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan lines-together; page-break-after:avoid; mso-layout-grid-align:none; punctuation-wrap:simple; text-autospace:none; font-size:11.0pt; mso-bidi-font-size:10.0pt; font-family:Arial; mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman";} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> </STYLE> Time has passed, and here's what has transpired in the past two months:I took the car to my local dealer. Diagnostic testing indicated a problem with the accelerator pedal assembly, which they replaced under warranty. Before the repair was done I could not feel the car shift into fourth gear at all; since the repair I can now feel it shift into fourth, but the poor fuel economy remains the same.
<!--[if !supportEmptyParas]--> <O></O>
The transmission is the Aisin 81-40LE, an ordinary 4-speed, with torque converter lockup. It is found on all Aveos made from 2004 to 2010. I recently obtained the Aisin service manual for this transaxle. There is a graph indicating the manufacturer’s specification for shift points. (The graph is stated in KMH, so I’ve converted the figures to MPH for this discussion.) The points vary slightly according to the throttle position (TPS) reading. On my car I have a scan gauge that reports the actual TPS reading. Slow acceleration is about 25 TPS; brisk acceleration is about 35 TPS.
According to the graph, at 25 TPS the shift points should be at about 11, 20 and 27 MPH. At 35 TPS it should shift at about 12, 22, and 32 MPH. Here is what I am actually getting on my car at about 30 TPS, which is moderate acceleration: it up-shifts at approximately 15, 25, 32 and the torque converter lockup does not occur until 45 MPH. In other words, all the shifts are delayed. Most 4-speed transmissions shift at approximately 10, 20 and 30 MPH and reach converter lockup by 40 MPH. This very delayed TC lockup, which does not occur before 45 MPH, accounts for the poor city fuel economy.
I live in suburbia. On major roads here the typical speed limit is 40. In traffic it is usually impossible to reach 45 – thus our Aveo is spending most of its time in the lower gears and the TC lockup is never actuated. If it were to lockup sooner it would yield much better fuel efficiency. Without engaging converter lockup there is no way this car will ever yield the estimated 25 MPG in city driving – no matter how it is driven.
<!--[if !supportEmptyParas]--> <O></O>
Transmission shift points are entirely determined by the transmission control module (TCM), which was designed and programmed by Chevrolet. The shift points with which it is programmed differ widely from the documented specifications of Aisin, the transaxle manufacturer. When I visited my Chevrolet dealer to ask if the TCM could be reprogrammed they told me that they could do nothing to change it, unless Chevrolet had issued a service bulletin for an updated program. This has not been done in the past five years that Chevy has been using this transmission in the Aveo. In other words, unless and until Chevy engineering rewrites the programming of the shift points and offers it as a software update for dealers to install, nothing will rectify this engineering deficiency. I then visited my local transmission shop (AAMCO) and asked the same questions. They confirmed that there is no way to reprogram the TCM unless Chevrolet rewrites the programming for it.
<!--[if !supportEmptyParas]--> <O></O>
From information I have obtained, this is a very common complaint for Aveos. Most owners are unaware that their cars are late in shifting, but are expressing frustration with their poor city MPG. Since the actual TCM programming is divergent from the documented specifications of Aisin, this amounts to a defect in that the car does not up-shift when it should. I intend to pursue this complaint with Chevrolet until it is resolved.
CF Active Member
Joined: May 2009
Posts: 119
Likes: 1
From: Daggett CA
i have a 08 with the 5 speed. if your only getting below 25 mpg it's due to the auto trans. what little city driving i do, i getting about 30 mph. but i get between 36-38 highway @ 70 mph. with the AC in. if i run 55 to work i can see almost 40 mpg.
good luck on your fix..but a lot of people have reported poor fuel millage. i think a lot has to do with where people live, and the biggest is how they drive..
good luck
good luck on your fix..but a lot of people have reported poor fuel millage. i think a lot has to do with where people live, and the biggest is how they drive..
good luck
CF Beginner
Joined: May 2010
Posts: 7
Likes: 0
latest measurement i get = 13.56km/L 80-90% highway with some amount on city driving and traffic jams in the highway (yes, we paid to go on tolled highways to get jam in my country)
this converts to about 31.9mpg
not too bad i would say...but the problem still lies in horrible traffic conditions where it is only about 20mpg in my case....
this converts to about 31.9mpg
not too bad i would say...but the problem still lies in horrible traffic conditions where it is only about 20mpg in my case....
i have a 08 with the 5 speed. if your only getting below 25 mpg it's due to the auto trans. what little city driving i do, i getting about 30 mph. but i get between 36-38 highway @ 70 mph. with the AC in. if i run 55 to work i can see almost 40 mpg.
good luck on your fix..but a lot of people have reported poor fuel millage. i think a lot has to do with where people live, and the biggest is how they drive..
good luck
good luck on your fix..but a lot of people have reported poor fuel millage. i think a lot has to do with where people live, and the biggest is how they drive..
good luck
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