S Mode & ECT Use for Mountain Driving

The engine brake feature is accessed in S mode. Owners’ Manual, pg 186:









 

no, you can't do harm. the ECU won't let you. Use whatever gear you want. you'll figure it out.

 

Ok. Well I did S4 so I guess I’m good. But I noticed zero engine braking. RPMs didn’t really jump. Stayed around 2 to 2.5k going 45 to 50 mph. Guess I’m fine.

 

I tow a 5,000lb trailer a lot. The only time I’ve used S2 for engine braking was descending Wolf Creek pass in CO, it was a 25mph speedlimit on a 7% grade.
Generally I tow in S5 and only use ECT for engine braking.
Another thing to pay attention to is transmission temps, the pan temp and torque converter temps. The torque converter only locks up in 4th, 5th & 6th so if you’re climbing a hill on 3rd your temps will rise quickly…
Photo of my OBD fusion app dashboard as I summited Wolf creek pass showing various info.

 

There’s a portion on the Mauna Kea ascent that is gravel and requires 4wd, I’m not sure 4lo is a requirement.

However there is another road that goes down to Waipio valley that is the steepest paved road (40/45% grade) in USA and that also requires 4wd (guard at the top stops vehicles) and that does have hairpins. You just have to selectively use 4wd, although you do hear pops and tire squeals from other people that don’t

 

i didn't even know that screen existed

 

To think of it simply if in D the car will choose 6th gear and lower.

If in S4 the car will choose 4th gear and lower by default. So if cruising at 50mph and slow to 20mph the car will choose the correct gear but won’t show you on the dash. If you come to a stop and start off again the car will start in 1st, 2nd, 3rd and go to 4th.
Same goes for S3 and S2.

If you want to see what gear you’re in whilst in S mode you need an app like I showed earlier.

 

Did you have ECT on? ECT will hold the gear at higher revs and will select a lower gear compared to without it switched on.
If you still do not feel engine braking (which is essentially just the engine reving high when going down hill without your foot on the accelerator) then select the next lower gear, S3. The car does not know what speed you want to be doing so you have to guide it by selecting the different gears and occasionally using your brakes.

 

Since I was in 4th that whole time, was I in any danger temp or lock up wise?

 

are you talking about brakes, engine, or transmission? your brakes might get a bit hot if you are using them a lot. your engine and trans temps are fine. if you are worried you can buy an OBD2 bluetooth adapter and monitor them with your phone.

 

I didn’t have ECT on. The dealership told me that was mainly for towing. I was tempted to use it on the uphill climb but didn’t.

 

try it next time. it's not just for towing. it's for enhanced performance basically. Think of normal mode as economy mode tuned for MPGs. it really shines when climbing mountains.

 

No, temps will rise when climbing and the torque converter is unlocked... This is a whole different subject and quite difficult to understand/learn/teach. Ultimately unless you're towing or driving big loooong climbs into a headwind you will not need to worry about overheating the transmission.

Yes it's mainly for towing as it holds the current gear higher into the rev range and will downshift more frequently compared to not having ECT selected.

When I'm towing at 63mph in S5 for example it'll stay in S5, if I switch ECT on it selects 4th gear which I don't want. I only use ECT for engine braking down hill. When towing I use S5, S4 and S3, tbh I wish I had a manual gearbox but my truck configuration does not come in a stick shift.

 

ECT can be for engine braking? Man - just when I thought I couldn’t get anymore confused. I’m about to just stick with regular old D going up and down the hills and let Jesus take the wheel. Lol

 

ECT is mainly focused on changing the shift points. Typically the transmission is looking to be its most fuel efficient and will change gears as often as it wants to make that happen. ECT tells the transmission to go ahead and hold the revs a bit more and really only shift when needed rather than for efficiency. This is better for keeping your transmission temps low and also happens to make it a bit more "sporty" in normal driving!

 

S mode = Sequential Mode. Its a limiter for what gear your truck will be in. S4 = Truck will shift from 1st gear through 4th as needed but will not up shift to 5th or 6th gear. S3 = Truck will shift from 1st gear through 3rd gear as needed but will not shift to 4th, 5th, or 6th. S2 = Truck will shift from 1st gear to 2nd gear but will not shift higher to 3rd, 4th, 5th, or 6th. S1 = Truck will not shift above 1st gear.
1st Gear I believe is generally thought of as the crawl gear. Meaning its for low speed use only. Think max 10 mph. 5th & 6th gear are overdrive gears essentially that are there to help you with fuel economy.
ECT = Electronically Controlled Transmission (I believe). It changes the shift points a little to allow you a little extra power when you need it such as when you're towing or when you're ascending/descending steep hills in the mountains.
Regarding your fears of using said modes, I wouldn't sweat it. The computer won't let you do anything ridiculous as long as you don't do it intentionally. If you're driving 65 and try to use S2 to get it into 2nd gear, it won't let you do it because that would probably grenade your transmission. Pressing ECT while driving won't magically shoot you out of the front window lol. You're fine. I highly recommend playing with them in a safe environment where you are comfortable however if that would make you feel better.

The only thing you should be careful of in my opinion is using cruise control in the mountains or any time you're descending. With cruise engaged, the truck will brake without telling you, the only way to know is by paying attention and feeling it brake or by observing your speedometer. As long as you are aware of that, you should be fine. I wasn't aware of it and like I said in my previous post, I almost lost my braking power because of it. I was under the impression the cruise was using engine braking only but it seems it also engages the physical brakes and given enough distance descending, it can cook your brakes. Besides that, using cruise in the mountains (at least radar cruise control, not the regular) will annoy the shit out of you. It constantly revs up to catch up to the car in front, then inevitably brakes then when it feels it needs to speed up, it goes back to giving it full throttle and that gets annoying fast not to mention possibly dangerous. Not sure if it would cause any extra mechanical depreciation but I imagine over time if you do it enough, it would degrade the life of the engine.

Other people far smarter and educated than me can correct me if I'm wrong in any part of my analysis.

 

Excellent write up. Thanks.

 

Thank you. Very helpful. Curious about this part - “The computer won't let you do anything ridiculous as long as you don't do it intentionally.” —— what could you do intentionally other than red line it at the top or the cruise control thing? It sounds pretty foolproof. Which is good. Because I’m a damn fool.

 

in a manual, you can downshift at too high of speed and overrev the engine. the automatic won't let you do that if are you in s-mode. so if you try to downshift into 1st while in s-mode at 80 mph it will just not let you do that.

 

In the automatic - what happens if you set it to S2 but red lined it? Would it auto shift to S3 to protect itself or would it allow you to continue to redline it since you chose S2 and it’s not supposed to go higher than that gear?

I wouldn’t do that. Just curious. For my purposes, it seems S3 to come down a steep hill with lots of switch backs will work. I’ll be around 40 mph when I bump it to S3, which should be fine, and I can just bump it back to D at the bottom of the hill from S3 as long as I’m under 60mph, right? Other than that. I don’t see myself using this feature.