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Toyota/Lexus transaxle shift delay
Mr_Shiftright
Member Posts: 64,481
This topic is more of a technical focus on the causes, characteristics, and speculative solutions to peculiar shifting behavior noted by some of our members in a range of Toyota/Lexus vehicles, various years, various engines. it is open to owners and non-owners.
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one would think the word transaxial is perhaps unnecessary and possibly misleading.
my sincerest thanks shifty that you leave a place open for honest open discussion on this issue.
For instance during coastdown does it upshift due to gas pedal fully released, or does it only upshift if the driver hesitates, only briefly or momentarily, in an intermediate position? Say somewhere between the prior "acceleration" position and the throttle fully closed gas pedal position.
Some of this might even have to do with how often the ECU reads the gas pedal position. Remember that it must make two readings (redundant feedback sensors) virtually simultaneously and cross check the two to verify validity of the position. And what happens if the gas pedal is in motion, moved, between the two readings?
In any case if I'm the driver and I simply release gas pedal pressure slightly I would fully expect the result to be an upshift, absolutely an appropriate reaction to my input.
On the other hand if I release the gas pedal from an accelerating position to fully released, QUICKLY, I would expect the ECU to determine that I want "full" coastdown mode using engine compression braking in the current "low" gear.
(The above theory is quite thoroughly "muddied", of course, by my FWD "safety" theory wherein engine compression braking should never be used.)
But let's go forward with the thought that we happen to have a driver that hesitates, is hesitant, in changing gas pedal positions.
Once the transaxle upshifts into an inappropriate gear ratio for even slight acceleration, only quick, rapid, and CERTAIN repositioning, any position, of the gas pedal and HOLDING that position will suffice.
But that got me to thinking.
For eons upon eons (making a point) the springs used to return the throttle butterfly valve to fully closed had to be quite strong and heavy. If you took your foot off the gas pedal the last thing the manufacturer wanted to have happen was the throttle valve getting stuck open due to a slight cable bind or maybe a wee bit of debris in the way.
But that throttle valve return spring, even if still required, no longer serves to also return the gas pedal to the neutral position. Nor does it provide back-pressure against your foot as you apply gas.
So, with Toyota's implementation of DBW, just how strong is the spring that provides back-pressure against your foot?
For those of you with Toyota DBW, is it easier to leave the gas pedal slightly applied due to a weaker spring when your real intent is to fully release it?
WOW...
Remember the few discussions/rumors early on about left foot braking might be a cause? If you brake with your left foot then might you "rest" your right foot on the gas pedal? A DBW gas pedal with a very light back pressure return spring....
Okay, say you were to do that somewhat consistently, rest your right foot on the gas pedal while applying the brakes with your left foot.
Wouldn't the "learning" algorithm of the engine/Transaxle ECU be perfectly justified in recalibrating the gas pedal neutral position as the one slightly "in" due to foot pressure. Remember the brakes are being applied, why would the ECU "expect" the gas pedal to be anywhere but in the neutral position during braking?
Anyone want to try a strong, really STRONG, return spring on your DBW gas pedal?
RX330 2004 Electrical System Diagram Pub No EWD563U page 177.
As of 2004 it appears that there was/is only one "module", "Skin Control ECU with actuator" controlling all VSC functions, including ABS & Trac.
The above sentence is under:
4. Mutual System Control.
Amongst other things does that senstence mean that the engine throttle might be opened in certain situations to prevent engine compression braking from over-coming ABS brake release, moderation, functionality in lower gears?
Apparently the signal from the "Accel Position Sensor" is ignored if the VSC/Trac/ABS module has to take control of the throttle valve position.
That would certainly help to explain why the vehicle will not accelerate into a tight turn. But might it also help to explain the hesitation symptom?
Page 148 of the same manual...
"...It makes smooth driving possible by shift selection for each gear which is the most appropriate to the driving conditions at that time, by preventing dowing (sp? "downing"), squat and gear shift shock when starting off...."
For those of you having hesitation problems you might try applying a (VERY) light touch with your left foot to the brake in instances where you foresee the possibility of a quick return to "acceleration" mode.
The 2004 RX330 Lexus shop manual indicates that the transaxle will drop out of O/D the instant the brakes are applied. So just maybe it might prevent the upshifting of the transaxle during brief periods of coastdown.
The engine/transaxle ECU firmware appears to be sensing that the driver wishes to go into cruise mode when the gas pedal is released or slightly released (coastdown..) and therefore it quickly upshifts to attain the best fuel economy.
If instead you "apply" the brakes the ECU firmware is more likely to assume your wish is NOT to enter cruise mode but to slow the vehicle. It might therefore leave you in the current gear or maybe even downshift.
Constantly monitor the gas pedal position via the OEM hall effect sensors. If/when the gas pedal returns to the "neutral' position check to see which gear the transaxle is currently in and automatically change the "shifter" electrical gear control contacts (there is no mechanical connection) to "command" a one-level downshift.
If the brakes are applied simultaneously with the gas pedal being returned to neutral then "command" a downshift all the way into first. The vehicle will not downshift until the appropriate lower speed is reached.
In both cases while the transaxle may not actually downshift due to roadspeed being too high it certainly would not upshift and later leave you waiting 2 to 3 seconds for it to downshift back into the most appropriate gear ratio for the acceleration level dictated by the new gas pedal position.
If these were RWD vehicles I wouldn't hesitate to bring such a product to market but with FWD we would be incurring the liability that arises from FIRM engine compression braking on the front wheels.
For what it is worth, I have an 05 V6 AWD Highlander that drives perfectly, with no hesitation problems at all. I have two coworkers who also have that car (04 and 05) and have no problems at all, and love their cars as well. You will find many, many very satisfied owners who love their cars, like we do. There are two million cars on the road with the V6 5 speed drivetrain and those who actually report a problem are a very small minority.
Also, you should be aware that the majority of the posts about this issue are by people who don't actually own one of these cars and have never personally driven one to experience the hesitation first hand. They enjoy speculating about the issue and are mostly well intentioned, but it is all based on second hand information.
And finally, there are also some posters with an obvious anti-Toyota agenda who may provide you information that is not exactly unbiased.
With that in mind, I personally think you should still give the Highlander a close look with an open mind, I love mine!
Good Luck
this is a problematic post though:
frogg, "Toyota Highlander Owners: Problems & Solutions" #3294, 11 Jan 2006 9:20 am
there was at least another post in the forum that was shut down where an owner didn't experience the issue at the time of purchase. perhaps he/she wasn't being sensitive to it while being distracted by being in a new vehicle, etc, etc. that's a possibility.
this is why it is so important for someone to capture objective data that we could graph and review sequence of events to get a better handle on what is being commanded and when, and what is the response and how much later.
i thought the other day of going down to a dealership and driving one of the vehicles in question to see for myself if i instantly noticed a problem, or could get the vehicle to exhibit the behavior. i just don't want to lie to one of the sales reps about why i want to take the vehicle for a spin. if i were looking for a vehicle for purchase, i would.
too bad we couldn't get some posters shopping for cars to do some helpful "lifting".
Just before race time, really too close for comfort, the car was finally re-assembled and when the engine was started it immediately went WOT and luckily was shut down before anything was damaged.
For some reason the engine control ECU had "forgotten" the parameters for the DBW gas pedal/throttle control system.
Picture this....
A technician laying upside down, butt on the drivers seat, head and shoulders in the brake/clutch/gas pedal "tunnel". At the same time the Saleen factory engineer, white shirt and tie, is standing behind the cab with one foot on each exhaust manifold of the big-iron Ford V8, laptop computer laying on the cab top in front of him.
The Saleen engineer has the technician alternate the gas pedal position between "neutral" and WOT while he manually moves the throttle itself to the same, appropriate positions, meantime using the laptop to "tell" the Saleen's engine ECU to "trap" the sensor signals to save the positional parameters to coordinate the throttle valve position with the gas pedal.
Often wished I had made a video of the procedure.
So, how does your car "learn" these DBW parameters, for learn it must. And does it continuously re-adjust those parameters from time to time if it decides the previous parameters are for some reason no longer valid? Floor mat laying lightly on the gas pedal for instance.
Or someone left foot braking???
I can imagine a VERY confused engine/transaxle control ECU should the gas pedal suddenly go "negative" from the previously memorized neutral position established while that floor mat was in place and now removed or someone's right foot being finally removed from the gas pedal after "resting" there even with the brakes applied.
I have no doubt that the previous "false" neutral gas pedal sensor parameter would be immediately scrubbed, erased, but how long would it take, and HOW would it, go about re-establish a "certain", for sure, neutral position parameter?
And just how would the transaxle "act" until a new gas pedal neutral position parameter is memorized?
I have no doubt that the previous "false" neutral gas pedal sensor parameter would be immediately scrubbed, erased, but how long would it take, and HOW would it, go about re-establish a "certain", for sure, neutral position parameter?
there you go. many moons ago, i suggested maybe we were dealing with a non-linearity in the accelerator or throttle position sensors. of course, they could be loosing their calibration due to mechanical slop or similar.
Don't think so, that way IMMHO the problem would be pervasive, more widespread. Additionally wouldn't that be a problem that Toyota could quickly address?
No, I think its a human factors issue exacerbated by a poor or flawed firmware design.
imagine as a supplier you maintain tight control on the mechanicals / electricals of both the pedal and the throttle body position sensors, some fallouts in hundreds of thousands applied to this manufacturer's vehicles seems statistically likely. the devices (if not optically encoded) would definitely exhibit non-linearity. if totally electrical (hall effect for example), well there has to be some transformation of the signal into the desired output characteristics, and we know semiconductors and the printed ckt boards they are mounted on can go flakey...imagine a bad solder joint, or a temperature or pressure sensitive ckt board trace fracture.
i'm sure you'll agree: there *has* to be a mechanical to electrical translation and back with these two assemblies. you're not going to be able to replace just the electricals or mechanicals, so you have to swap the combination most likely. who knows, those assemblies may actually be more expensive than the TCM.
another thing i found interesting re: that particular post is that the service manager went as far as to replace the valve body in the transmission, which didn't solve the problem, and i can't figure out why the TCM wasn't swapped next; but KUDOS to that SM!
wish i new more about transmission mechanicals. it would be funny if they replaced his whole transmission / torque convertor assembly and it still did it. seemed like the SM was really working for the customer until someone else said "enough".
hey, can a torque convertor be at root cause for lazy shifting?
i know it costs $$ to continue swapping stuff, but you'd think somewhere, they'd continue to swap until they identified root cause and fixed the vehicle.
for them to recommend arbitration is pretty interesting. that problem must be way outside the norm, and they are giving up.
It seemed clearly headed in that direction, and it was refreshing to see that. For the most part, it still seems headed in the right direction.
I was a little surprised though to see this totally unwarranted and untrue comment appearing in your post User77: for them to recommend arbitration is pretty interesting. That problem must be way outside the norm, and they are giving up.
I sincerely hope that statement--the last part completely untrue BTW-- isn't the beginning of a distinct change in the direction of this topic, and that irresponsible mud slinging which prevailed in other discussions won't continue here also.
I just think it's a good idea to try and avoid saying anything which might precipitate sidetracking what could turn out to be the best discussion yet. Pointing fingers and making rash conclusions isn't the way to go.
On a related topic, I don't think any company would recommend or even go into arbitration if they firmly believed they would loose. It would seem to me that it would be far less expensive to simply drop a whole new transmission into the car.
I also think that poster's complaint is a different situation and not necessarily a hesitation related issue.
With regards to the issue of over-revving being a separate issue/problem if you browse the various forums on the internet you will discover that seemingly one of the TSB revisions had this result. Some owners incurring the additional symptom have had the dealer revert the firmware to the previous revision and apparently that cures the over-revving portion.
My only reason for jumping in here was to correct a misunderstanding re who actually said what about arbitration in the discussion about frogg's case.
what sort of recourse do you think frogg has when clearly the dealership has shown an effort to work on some things to address the problem, then they won't do any more to track it down and fix it? can frogg drive the vehicle over to another dealership and tell them what has been done so far, or is the VIN / owner flagged in some way?
i'm not trying to sling mud. the other post was an honest mistake. but in the box the owner is in, it will be difficult to succeed with arbitration if there aren't subsequent attempts to fix it, correct?
You asked what recourse I thought frogg might have?
First and foremost I would tell him what I said in another forum just recently:
"Some advice. This is the internet. Impeccable sources don't necessarily amount to impeccable information. Hearing from the horse's mouth means little when the horse may have reason not to be truthful. Use your own judgement, and be cool."
Next I would suggest he contact Toyota regional rep and get something going at a higher level.
The owner states:
The dealership has acknowledged in writing that a problem existed (and that they thought they had fixed it).
It sounds to me like the dealership says they have fixed the problem and the owner contends that they have not. I would think at this point that after talking to the regional rep, if no resolution is reached then arbitration would be the next logical step. A third party arbitrator could make the determination that a problem does still indeed exist, and if so, what actions to resolve the issue the manufacturer must pursue.
Carefully document every step taken thus far, and document every result. Do the same from now on.
Consider getting an independent confirmation of symptoms experienced.
Keep cool, be polite but rigorous, and above all be honest and realistic.
Lastly, keep one's own council. Don't go into this thing with preconceived expectations (good or bad) one might get from these forums.
I am not a Lexus 'hater', and I DO own one of these cars. I actually love my Lexus - if I just didn't have to leave my driveway with it
I am in the process of a DTPA suit against the dealer, as well as a lemon law claim against the manufacturer - and I'm not just doing this all for the 'fun' of it. This is a REAL issue for me.
I will also tell you that between loaners during service and test driving other Lexus models in an effort to find one that doesn't do this - I have driven each of the following: GS, IS, ES, RX, and GX. A mixture of 06 and 05 model years, and I have driven each multiple times except for the IS. The ES is the only one that exhibited the hesitation issues at discussion here and in the other forum - and it exhibited it in each and every one I drove, except for one.
On a side note - I experienced a completely different transmission problem with the GX which I took home for the weekend - gear hunting in cruise control at about 80 mph, with no significant hills or other terrain changes.
I took both the local dealer General Manager, and on a separate occasion the Manufacturers representative, on test drives and they acknowledge that the issue exists. The Mfr rep actually drove my car while I was in it, and was able to get an even worse reaction from the car that I was. So, Lexus knows this is a problem - it just seems that they either don't know what to do about it, or are choosing to ignore it. In either case, I don't understand why they won't work with those of us that DO experience the problem. Only reason I can assume is that there are too many people with the problem, and therefore it would be too costly.
I can't wait until I can get a car that doesn't make me so unhappy - unfortunately, I can't do that until my claims are resolved.
Not much chance of success taking this route. I don't think DPTA is intended for these types of complaints.
Given this is about the umpteenth time we've heard how he hates his car, maybe it's a desperation move? Not a happy camper at all.
The voltage output from these sensors certainly, absolutely, should not "flutter" due to the input reference voltage nor to any design flaws within the sensor themselves, at least none that I can think of off-hand.
So the only thing left to consider as a source of "flutter" is the driver's foot.
P2120 and P2125 are the two codes used to designate that the accelerator pedal has been determined to be "fluttering" at the fully released position.
http://www.siennaclub.org/forum/index.php?showforum=39
Haven't heard much about hesitation in Sienna's here at Edmunds so was kind of surprised to find this forum where it is discussed so prominently.
I don't think it's so much a prominent topic (as in "widely discussed"). Rather, my sense it's a topic that is discussed prominently among a few (as in "narrow focus").
A poster who contends that he could demonstrate the problem in any car raises other questions. Would he hate my car, and those of my coworkers just as much as he hates his own? We think our cars drive just fine and are very happy with them. Makes me wonder.
Or as wwest suggested, the fix will result in violation of an emissions or fuel consumption regulation.
BTW, best not to respond to those who want to argue and make it personal.
I was curious if the intake noise from the Atkinson cycle's reverse airflow, combustion chamber back into the intake manifold, in a 3.3L V6 might be at least part of the reason the RX400h doesn't make use of this fuel economy method.
Inadvertently found:
July, 8th, 1999 Final report by SRI, Sierra Research Inc, on "Alternative and Future Technologies for Reducing Greenhouse Gas Emissions from Road Vehicles"
One of the conclusions is that if the industry switched to 5-speed automatic transmissions, made use of ASL, Aggressive Shift Logic (quicker upshifts), early torque converter clutch lockup, and shift into neutral with brake application and engine at idle, a 9.8% improvement in fuel economy would result. Industry response was that "driveability" would suffer.
Welcome to 2006.
I have found that I fully release the gas pedal in this car much more frequently than I do in other cars I drive. I noticed this before even reading this website. That is part of the 'problem' with the car and its hesitation that I have complained to the dealer about - the gas pedal does not respond proportionally to either pressure, or release of pressure. As a result, I find I have to completely take my foot off of the gas pedal frequently.
After reading your posts that this may contribute to the 'problem', I have tried to not do this as often...but given what I described above, this is very difficult for me to do.
The other thing I have noticed, is that the gas pedal (and brakes, for that matter) do not respond in the same manner consistently. For example, when you drive a car that has very sensitive brakes, you automatically adjust your pressure to the brake pedal within a few miles - and you don't notice the sensitivity anymore until you switch back to a car that isn't as sensitive; and you adjust again. The problem I have with my car, is that I cannot just 'adjust' to the way it drives, because it always reacts differently.
the "shift into neutral with brake application and engine at idle" sounds like what is happening as I come up to a stop sign and do not stop, or negotiate a parking garage.
And the "quicker upshifts" sounds like what happens when at speeds around 40 mph or so.
In both cases, when the car shifts into the proper gear, not only is there an inappropriate hesitation, there is a jerk/clunk when it does shift to the lower gear.
very interesting.....
My Internet research reveals there are at least Four (count 'em---4!!)Aftermarket Suppliers of "Transmission Performance Programmers", also called "Power Control Modules", sometimes called "Automotive Performance Computers" which are able to modify shift performance, shift points, shift firmness, and a host of other parameters for 4,5,and 6 speed automatic transmissions on every make or model of vehicle on the planet.
That tells me (1)There's no mystery or black magic to this issue, (2)The so called "unknown fix" isn't unknown--likely Toyota included, (3)A lucrative market exists for people to change the way their trannys work--not just Toyota/Lexus, (4)Cost is modest--prices range from $125 to $400 depending how sophistcated one wants to go.
All the confusing technobabble aside, in layman's terms, I no longer believe it's the mysterious and elusive quest we've all been obsessing about.
That said, here's what I think this issue boils down to.
All manufacturer's DBW throttle/transmission systems have unusual or unfamiliar characteristics. I believe those Service Tech's comments about it being a "normal" characteristic are probably correct. I believe it's likely a consistent phenomenon across the board--typical to a greater or lesser degree to all manufacturers. Auto manufacturing consistency today is higher than it's ever been, so anomalies like some suggest this may be aren't too prevailent any more.
So I believe that complaints we are seeing have more to do with a few owners having adverse sensitivity to the issue, and most owners not noticing it nor being bothered by it.
More research results. A small sampling to be sure, but revealing nonetheless.
Since coming into this issue last October, I've driven 12 Toyota/Lexus products with 5 speed BBW in addition to our own two cars. Lexus 330 and RX series, Highlander, Avalons, and Camry. None has exhibited any of the delay, lurching, seeking, or prolonged hesitation. All have been seamless, smooth and quiet. I have yet to experience any of this phenomenon, and I have yet to speak directly to anyone who has.
I appreciate that information and do find it informative. It also makes me wonder why Lexus continues to say nothing can be done. I also wonder why they haven't suggested such a product, since the local dealer and the Lexus representative both acknowledge and can repeat the symptoms in my car (unless there are warranty issues associated with such an aftermarket product...).
But I must vehemently disagree that I am just experiencing an 'adverse sensitivity to the issue'. I do agree that most owners are not 'noticing it nor being bothered by it'. But it is definitely more than a perception or sensitivity issue.
After reading some of the other observations and suggestions, I have been messing around with different driving 'styles', for lack of a better word. And the symptoms are definitely more pronounced under certain driving conditions and/or driving 'styles'. It is definitely some type of reaction by the software or hardware to the 'inputs' from the driver.
Having said that, I have not been able to find a 'style' where the symptoms are completely gone - THAT may be a function of my 'sensitivity to the issue'. But as noted in a previous post, the car doesn't react the same to the same inputs - so modifying my driving 'style' permanently has not been effective. Not to mention, I do not see anywhere in the manual where the driving 'style' required for this car is discussed.
I completely understand that you and others do not experience the symptoms that I experience, and I have event talked to others who do not experience this problem. But trust me, what I am experiencing is much more than just being 'sensitive to the issue' - and I am not the only once experiencing this, so it is definitely more than just sensitivity.
Good luck with your Lemon Law process. You have formed your opinion of the issue and based your action plan on that opinion--your choice is made; now let the chips fall where they may.
Nevertheless my perception on what this is all about has not changed, and likely won't, at least not in the near future. If it turns out my assessment is in some way incorrect, so be it. What I think about it is just my opinion. For now, I'll stand firm on what I feel is going on here. I'm quite happy with my vehicle status, and as I said earlier, I have yet to meet anyone who hasn't. I've actually met quite a few who agree with me. I don't expect that status to change much either.
I posted info about "performance enhancers" as simply info, and wasn't implying that anyone should rush out and buy one.
It simply proved to me there are numbers of commercially available devices out there, unrelated to Toyota/Lexus, which change transmission shift characteristics. Therefor the issue is fixable, changeable, modifiable, or whatever, and isn't the elusive and mysterious quest being bantied about by us. Toyota/Lexus have also offered a mod in the form of a TSB for those who want their transmission characteristics changed. For anyone not wanting to use what's already available, that's their call.
How you choose to resolve your "itch" is entirely your choice, and it's not my intention nor my place to interfere with it. I hope things work out for you.
Toyota and Lexus have long been ahead of the curve in implementing these new aspects before they become law and I suspect that this is just another case of their "leading the pack".
The only answer I can see for the future is to only buy cars with the sequential shift feature and then always run it under at least that level of manual control.
For those of you who might be interested it appears that ALL of these new 5-speed transaxles have the three electrical inputs required for sequential shift mode/operations but no connections to tyhe cockpit.
Good luck.
it's even responsible and realistic to assume the TCM or ECM or whatever of a particular manufacturer, applied to an OEM vehicle of one make and applied to other makes have different firmware.