I recently purchased (2 weeks ago) a 2021 RWD Toyota 4 Runner Limited 42 K miles from Dealer. (After much research, checking with other owners, checking reliability scores, etc. and watching some of your reviews, I decided this was the best route to go for reliability.) Before purchase I did all of the checks I possibly could--looked at multiple vehicles, checked VINS for flood, damage, etc. CARFAX, etc. Found this one that was absolutely clean and no rust or damage. (Except for some minor scratches and paint chips.) I also got the platinum warranty.
After purchase I went on a 200 M trip the next day for work. I noticed it was hunting gears between 30 and 40 mph and it would downsift, then upshift, then downshift again, then upshift and when I tried to accellerate, the engine seemed to lag way behind as it did not seem to have a gear.
I took it to the shop and the mechanic drove with me and noticed all of the shifting between 5th and 6th gear. He checked the codes and found none and then said he reset the "adaptive transmission" and it would take a while for it to relearn how I drive and to drive normally on the way home and this should fix the problem.
I drove home and went throug a week of driving and the issue as gotten worse.
On small downhills--even little dips in the road, the transmission downshifts, then upshifts again. I was going around a curve, slowed down and then tried to accellerate out of the curve to keep traction and the transmission was hunting all over the place and my engine was breaking. (If it had been raining, this could have been a wreck.)
I tried to accellerate in slow traffic to move into another lane and I had no power upon depressing the accellerator. I had to wait on it to find a gear.
I telephoned Toyota direct and they gave me a case #. I asked if they had some sort of technical support--for this shifting issue. They said I had to take it back to a mechanic for service. So I am going to make another appointment.
I was wondering if you knew what might be causing this issue. I cannot imagine that this would be the way it is supposed to work, as this has not been the case for ANY car or truck, standard or automatic that I have ever driven.
Thank you, I have some information--finally, after three dealerships and a pile of phone calls.
Update: The shifting issue on the 4Runner is apparently an “intentional” issue. I was able to meet with a Toyota Tech who is a “guru” on these vehicles. We drove together on the roads I drive with all of the tech tools hooked up. He indicated that the ECM was programmed to use engine load as the main parameter for shifting along with throttle position. He showed me the calculations on the computer. He also showed that the timing of my solenoids was near perfect.
This programming results in the transmission shifting in and out of overdrive at 1mph differences in speed and multiple shifts on small inclines and declines. This also kicks out cruise control if you go down a small incline on the interstate, as I found out--again thinking something was wrong with my cruise. It can also give the feeling of loss of power because of the shifting
He said the TCM and the interface with the ECM was programmed this way to “meet emissions standards.” It is not apparent on all vehicles because they may not be as efficient as mine. Also, if I drove a few of the off the lot, they likely had the logic reset after test drives.
This constant shifting around likely the reason I was averaging 23mpg instead of the listed 19mpg. So apparently instead of using aluminum doors and some lighter components, Toyota used the software to meet the environmental standards.
The reason it did not do it on the test drive was likely that they reset the logic. He said it takes about 20-50 miles after for it to kick in again. This is also likely why it worked fine when I drove it back from the dealer after they reset the logic and started again later.
It was nice to get some insight on how the calculations are done and exactly what the software is doing. He indicated that this is why the 2025 is going to be a full re-design.
Apparently, there are other drivers who complain about the issue. The better the vehicle is working the more it irritates the driver.
It would be really nice if Toyota would issue an update to widen the paramaters between up and down shifthing so that when we have to drive on these wavy roads it doesn't do this--because if we are all driving around in S-4 it totally defeats all environmental standards. I am seriously hoping Toyota will consider a softare update.
Scotty doesn't answer follow-up questions, unfortunately. Independent mechanics have very high level scan tools, and a really good one can tell if the transmission it starting to slip without you actually feeling it, especially with these new, ultra-modern vehicles.
Has long as it shifts within a margin of error as dictated by the ECM/TCM, it won't trip a code. That's when you try to problem solve using live data, and it'll come from experience. If you're relatively nearby Scotty, set up an appointment as discussed in the FAQs and road test it with him in the car. Here's the hyperlink.
https://carkiller.com/scottykilmer/postid/158877/
Good luck!
Also, if anyone else is having this issue with no codes, definietly get a technician to drive with you and have all the scan tools hooked up--someone who knows how to use the software. It will save you a pile of money and trips back and forth. The issue is you have to request that--and a good dealership won't argue with that. It costs way less than having them run diagnostics ever week. (A friend just had a situation where the tranny would not go into overdrive at all--turned out it was a sticky throttle-body injector. Becaue engine load was high the transmission would not ever shift--also on a relatively new car--it didn't have a code for a sticky injector--but the scan tool caught it. LOL)
Of course, they're not supposed to work that way. Pat, you should have listened to my advice that I give over and over again and that's this, never buy a used vehicle unless a mechanic like myself checks it out for you first. It obviously has some type of transmission problem and mechanic like myself would have seen that when road testing it and would have said don't buy it. But now you have it so you're stuck in the middle. And realize hardly anyone knows how to rebuild those modern transmissions. Most guys just replace them. They don't fix them. Good luck though. See if you can find a Toyota guy home. Asks with the transmissions and has the Toyota dealer level scanner to see what's going on because for a problem like Dad codes are off in Muni unless they don't trip codes for stuff like that most of the time. But there is a lot of data in the computer that a trandy guy can analyze to tell you what system is starting to fail
Thank you for the advice. Follow up here: I don't know that it would have been discovered if a mechanic drove it, since it was around 100 miles when I first noticed it and they don't let you test drive them that far around here. The diagnostic done at the dealership showed no codes at all when I had it looked at the first time. It qualfied for a bumper to bumper premium warranty when I bought it and I did purchase that premium warranty as an extra.
I took it back to a service center. They scanned for all codes. There said there are no codes. They said they looked at the computer history and there was nothing indicating anything going bad,
They test drove it and saw the problem, they also said oweners of brand new Tacomas are complaining about this same problem--they even said "it started when they changed to the new transmission in 2019". they said my issue was very pronounced, but if they cound not find a code there was nothing they could do.
I asked if they checked the transmission fluid physically--not just for codes. They did not, so I requested they do that. I had to leave it over night because they could not get the transmission to cool down enought to open the transmission ports. I am waiting on those results.
I am covered if the transmission falls apart, in fact, it would have been great if it did that--my big issue is that they don't even acknowledge that there is something wrong. It is like, if it is not "in the computer" it doesn't exist even though at both dealerships, they can clearly see it is shifting all over the place.
I seriously wish Toyota would acknowledge this problem and find a fix--because apparently it would not only make me satisfied, but a lot of Tacoma owners, as well. I am hoping they finds something in the fluid.