2022 Transmission High Temp Alarm

Ah got it. Thanks for the reply.

 

I'd be a little surprised if there isn't a TC sensor, too. Hopefully the scangauge folks can find a way to read it.

 

Hopefully ODBLink/OBDFusion come out with the 2022 Enhanced diagnostics for Toyota. I have the 2011 one for my Lexus and the amount of PID's available are insane. I can see PID's for the module that controls my drivers seat.

 

Well my truck is having a sleep over at my Toyota dealer today and they are checking over the transmission.

The service manager was a really nice guy and we actually went for a ride and replicated the issue on the same FSR that my second event occurred. It happened at the exact same place as well with cooler ambient temperatures too.

He was honest tho, and documented my 35” tires and the camper on the back, for Toyota Engineering to make an assessment. He did agree however that the road conditions really shouldn’t be bringing in that warning condition, even in 4Hi.

He said he was back and forth with Toyota today and hopefully I’ll hear an answer one way or another tomorrow.

Possibilities include:

1. Normal, but exacerbated by being at max gross weight.
2. Transmission Cooler bypass not functioning correctly.
3. Software, as in its keeping the cooler closed too long.
4. Low Fluid level
5. All of the above or a combination.

I will report back.

 

from what i remember usually its best not to let the transmission sit in auto but to leave it in a selected gear that is 1:1 ratio. for the 22 tundra its 7th gear. that way the TC wont lock/unlock all the time. kills mpg though.

use to do this on my 16 tacoma and 14 4runner.

 

That’s not how this transmission works. It locks up in low gears, lockup will engage in 2nd with low throttle and 3rd with mid throttle, but definitely locks up in 4th gear. If you put the selector in S7 from D, it still behaves like D except you’re just telling it to not shift up beyond 7th. If OP was driving 20 mph, they were probably in 3rd with high throttle so the TC was unlocked. Driving 25~30 mph would probably put the transmission in 4th with lockup. That would greatly reduce the heat generated in the ATF.

 

Does the TC lock up in first gear? I have a steep hill coming up from our barn where I store our camp trailer and just put it in 1st thinking it would lock up but the truck actually does it in 2nd if I don't manually shift it to 1st.

 

I don’t think it does. Even if you select S2, the transmission may remain in 1st depending on the TCM’s shift point tuning.

 

If its that steep and the tranmsission temps are a concern I would be in 4Lo. I move my trailer around my relatively flat yard in 4Lo. Makes it a brake modulation thing instead of a throttle modulation thing.

 

It’s not really that strep though. Just standard FSR grade that logging trucks use.

In 30 years of driving trucks I’ve hardly ever used 4Lo but there’s always time to change ones habits

 

Seems the dealer needs another day to crunch on the issue. Toyota Engineering is making up their mind with a path forward.

 

on 2.5 gen's the alarm point is 302F.

This scenario can happen across many vehicles even with an auxillary transmission cooler. For example, many "overland" built 4 runners will still hit the temp alarm even with factory in-tank cooler.

The main issue that folks have correctly pointed out is that in 4 hi and low speed you have a great combo of things to work against keeping the transmission fluid cool. Low speed has minimal air flow (yes the fans are working but compared to 30+ mph it is a pittance) and 4 hi gearing isn't low enough to reduce load on transmission and the torque converter. in 2.5 gen's in 1st gear the TC doesn't lock, ever (at least in 2019+).

Overall, all OEMs are pushing transmission temp limits higher and higher. The good news is that Toyota builds an amazingly tough transmission.

 

Seems they didn’t find much wrong with the transmission or cooler. Toyota engineering is going to mull it over a bit.

They did however weigh my setup and it is approx ~150lbs overweight (with driver and 1/2 tank of gas) in current configuration, which unfortunately opens the door for them to deny warranty down the road. I saw that coming but meh. I certainly won’t be the only customer who has some excess weight onboard.

The tech took it back out and did replicate the alarm condition however the coolant temp was only 212F, which shouldn’t ring in any alarm. They then reset the computer and tried again, at which point it did not go into alarm.

All the cooling lines were inspected and all are normal as well as the fluid level.

So back into the void I go. I’ll be extra prudent and either manually shift or use 4Lo going forward in similar situations.

 

I am interested in a high quality aftermarket cooler. However are they universal? Or do I need a custom one made for the new Tundra transmission?

This truck is so new that the aftermarket is way behind.

 

Looking through the data it does appear the 22+ Tundra only reports one transmission temperature. The rest of the supported data looks the same as previous years. If there's anything in particular anyone would want to monitor that the ScanGauge III doesn't currently report I'd be happy to look into it.

 

This was talked about on another thread. My reply was that the only reason the 2.5 gen has an almost OEM looking cooler kit is because one of the members here put in the leg work and made a kit. It is a badass kit, like I said it looks OEM and uses the OEM parts from previous tundras that did bring an actual standalone cooler. I have it installed in my truck and still haven’t seen over 195*. To this day, I have never seen an actual kit specific to the 2.5gen or many other trucks for that matter. I wouldn’t wait for one either. So I would start digging and see how you can add one. Like you said, the dealer notice the tires, camper and overweight. Definitely a denial of warranty. And I am 100% positive that that trans isn’t cheap.

 

I agree with you completely. I’ve got a trip to Colorado coming up from BC and back and will monitor the temp on my Scangauge 3.

When I get back I’ll see if I can get a kit similar to the one mentioned in my other thread.

The Derale unit looks promising to me. It’s just a matter of mounting it…

 

That kit is nice, but a fan isn’t really needed. Look over on the 2.5 forum and search for the kit. Never mind here is the site. Those are good coolers.
https://genuinecoolingsystems.com/

 

True enough on the need for a fan most likely, but at slow speeds it'll help. It's on a thermostat set at 185F I think so if it's cooling enough it won't even be on.

 

The previous gen also has a t-stat built into the trans and is also 185. Fan is nice, if it fits then yes. Only thing it can do is help.

 

Are you getting the "Transmission Oil Temperature" warning? I got that towing a 6,000lb travel trailer up a steep grade doing 70mph. I brought it down to 65mph and that seemed to resolve the issue. The air temp was 90 degrees.

 

My '12 holds around 203-208 in the trans pan no matter what the conditions. It gets there in a hurry too. I think it's a 200° thermostat. I guess there is the possibility it changed with model years. That would be interesting to know. I'd definitely swap to a newer t-stat if it opened 15° sooner.

Fwiw. I added an additional cooler after the stock cooler. My return line is cold even after heavy towing in 2nd and 3rd up a steep pass. It was 60°F ambient, however. Still 200 in the pan.

 

Yes that’s right.

Transmission management seems to have abated the issue. « Tow Haul »
Mode keeps the temps down quite well, as well as 4LO if I really need it.

 

Not sure on the t-stat temp. Other years could be higher temps. On my 20, after installing a cooler it goes up to around 189 and stays there. Obviously it fluctuates but not much. So yours might be a higher temp setting.

 

On my last big trip to Colorado from BC the transmission would cruise at 80mph with the camper at 95C (203F), which is right around the same temp as the rad coolant. The highest I saw on the trip was 100C (212F).

It my understanding that these transmissions run hotter than previous, being a completely different unit.

Im still not convinced that an external cooler with an electric fan isn’t a good idea long term though. Shouldn’t hurt.

 

my personnal opinion the the radiator end tank cooler is that they have a fatal flaw, which is that they rely on the coolant to be flowing through the radiator. The problem is that there are situations where the transmission needs lots of cooling and the engine does not and so the thermostat closes and cuts off most of the flow through the radiator. Then the trans fluid is just looping through the radiator with minimal heat exchange.

I am fairly certain this is what happened when I towed my trailer with my GX. The transmission would get up to like 240F on climbs. I would pull over to let it cool, but the temperature just wouldnt come down. It would literally take 10 or 15 minutes. The engine coolant temp would drop almost as soon as I pulled off the road and the fact that the engine was just idling meant the thermostat was just barely open so most of the coolant was just bypassing back through the motor.

I know Ford now has a liquid/oil cooler under the truck and has its own cooling look which doesnt involve the radiator. They still can get hot though.

 

The tranny will have been designed with an optimal temp range in mind. I doubt an additional cooler would pose any issue under most conditions but it is possible to have temps too low as well. I believe the most recent 2.5 gens ran a heat exchanger for the tranny that doubled as a cooler and "warmer" to get the tranny up to optimal temp quickly.

 

This may be irrelevant to your comment, but....

The 2nd gen tundras did not rely on in-radiator cooling. It is a separate unit appended to the A/C condenser.

The exception to this was the 19-21s that rely solely on coolant that is piped back to a small heat exchanger on the side of the tranny. It's actually called a "warmer". Earlier trucks also had the warmer.

If I ever buy a 19-21, I would make sure it hasn't towed and I'd install an aftermarket right away.