2015 Nissan Rogue, Colorado. Can't make it up I-70 into the mountains (and home!).

I end up at 40 mph, accelerator full down, it won't go above 2800 rpm and can't accelerate uphill. Some times it fluctuates in the 2700 rpm range, 2600-2700-2600-2700.... We installed the 4-port beehive and the transmission oil cooler, but yesterday, post install, same issue. On long segments of uphill, it won't downshift, and I slowly lose velocity and well, it's dangerous. At one point, I pulled over, and then, after stopping, couldn't even get above 1000 rpm. After turning the car off for 10 minutes, it started and worked. What should I try now...post oil-cooler install? ideas? (Yes, I got the letter from Nissan, but the 2015 doesn't qualify for it.) Any thoughts would be greatly appreciated! TIA.

What kind of cooler did you install? If it's one with a built-in H-valve (bypass valve), ditch it for one that's a straight-through with no valve. I've discovered some rude things lately about H-valves on Nissan products with van and SUV body styles. They heat up more than they should under heavy load conditions and don't shed heat the way they should when the H cracks open. To monitor what's going on, do yourself a huge favor and get a copy of the CVTz50 app and a VeePeak VP11 bluetooth adaptor for your OBD port, so you can spy on both your CVT and engine.

no H-valve on the cooler I believe, just in and out....in an S type design, it is a Hayden, 7 1/2" x 12 1/2".
I bought the VP11, had already purchased the CVTz50app but couldn't get it to work with my current adapters. We shall see!
Thank you VStar!
Linda

I have received the VP11 and found these codes with the cvt: P0725: Eng Speed Sig and P0744: A/T TCC S/V Functn
are these codes typical for overheating CVT temps and inability to get up a big, long-a$$ hill?

Around town, my CVT temp appears to be between 82-85 C, which if I read correctly in this forum, the best range is 80-105 C, so that's good, right? (I live at 8500' MSL if that makes a difference.)

The CVTz50 also shows that for 07/22 and 08/22, I had zero CVT Fluid deterioration, but for 9/22 , my CVT fluid deterioration jumped from zero to 105,724. I had my uphill driving problem on 9.1.22, so I guess that could be accurate? but then on another screen it shows Average and Max CVT Temps for 9/22 as both being 82 C. So hmmm?

What is this CVT A/B count that I see people write about and what should I be paying attention to there? I only see CVT Temp/Count and it being at this moment 86 C/171

should I just wait til next time I drive back up into the mountains and see what the CVT temp does? or is there anything else I can check? or maybe winter will fix my problem...

Thanks for any help! suggestions, ideas!

To get CVT-A/CVT-B you need to go to "CVT INFORMATION" from the CVTz50 home screen.

There's more than one thing going on here. P0744 is a torque converter lockup code, it means the TCC solenoid worked electrically but the TCM didn't see pressure to the TC clutch. That should NOT cause a hill-climbing problem, just reduced performance and no TC lockup. The P0725 is a different animal, it isn't really a tranny code. It means something went south in your engine which caused the ECM to stop transmitting an engine speed signal to the TCM. There's probably a C1130 in your ABS for the same reason. Read your ECM codes, there will be something in there that caused your engine to go failsafe.

No engine ECM codes. just the two CVT codes above.

Well anyways, today I drove 2 hours slightly downhill, and yes it was freakin hot (98F) and only slightly downhill, but over the 2 hours my CVT temp went from a nice 85C to 116C...no fail safe mode as far as I could tell, but it was slightly downhill and I was maintaining 1800 rpm for 60 mph, not trying to accelerate, so who knows?

On the way back home, only 85F outside, slightly uphill, but got to 106 C on the CVT. No issues with fail safe, but I know these temps are too high.

I had installed a Hayden 7 1/2" x 12 1/2" vertically in front of the radiator (per instructions), but maybe I should get a bigger Hayden? temps seem high. Any suggestions?

That P0725 must have been a leftover from some past incident, then. Only loss of comm can cause that code, it never occurs without a problem in some other system, usually a DTC in the engine.

Yah, a bigger cooler or maybe continuous forced air through the one you have. You're not the only one here with a van or SUV having that issue, so I have to think there's some hidden design issue with ventilation on those body styles which is causing this. I did a test recently which showed the radiator outlet tanks on an R52 Pathy got much warmer after an uphill WOT run than a Max or Altima. Differences in plumbing between the Pathy and Max are minor, so airflow is the only thing which can account for that. The Quest seems to be most vulnerable based on what you guys are telling me, but the gen2 Rogue seems to be vulnerable too.

Let me think about this, maybe there's a way to fool the ECM into turning the fans on full speed based on CVT temperature and not just engine temp. On a highway run with the A/C on, they were probably only running at low speed. Extra air is probably the right answer if there's a reasonably-painless way to accomplish it.

I installed the Hayden directly in front of the radiator, which is in front of the fans. So the Hayden is the first thing to see the ram air. Was that correct? I see info on the Hayden site that says to maybe put it behind the radiator (but there's no room for that). Maybe I run a hot wire to that fan to have it on all the time, or maybe include a switch so that I can turn it on/off high speed?

My work commute is 2 hours down and then back up into the mountains! really hot here in Colorado these days, but last night the CVT temp of 106 happened with outside air temp of 70 deg F. on a 45 min drive, relatively flat terrain.
Thank you!

torrc wrote: ↑

Thu Sep 08, 2022 6:32 am

I installed the Hayden directly in front of the radiator, which is in front of the fans. So the Hayden is the first thing to see the ram air. Was that correct? I see info on the Hayden site that says to maybe put it behind the radiator (but there's no room for that). Maybe I run a hot wire to that fan to have it on all the time, or maybe include a switch so that I can turn it on/off high speed?

My work commute is 2 hours down and then back up into the mountains! really hot here in Colorado these days, but last night the CVT temp of 106 happened with outside air temp of 70 deg F. on a 45 min drive, relatively flat terrain.

Take a look at EC-48 here and you'll see the root of the fan problem:
https://www.nicoclub.com/service-manual ... 5%2Fec.pdf
Notice that unless the A/C pressure or engine temp go way up, the ECM shuts the fans down completely at anything above 50mph. That's fine for the engine and for gas mileage, but on a 100 degree day at 80 mph, the engine is working fairly hard and outlet tank temperature rises even though the coolant temp is still within bounds. That causes a loss of heat exchange efficiency to the tranny, but the ECM isn't programmed to react to that.

Even putting in a fan switch won't be particularly simple because of the way Nissan configures their 2-speed fans. Here's how it works, The first WD is low speed, Relay2 turns on, Relay1 and Relay3 are off. Relay 2 puts the fans in series, electricity follows the red and orange paths to ground (blue). Because they're in series they each get half the juice and run at half speed:

Now here's how it works on high. Relay1 and Relay3 are on, Relay2 is off. Each fan gets power and ground from a different leg, Fan2 has permanent ground but now gets power through Relay1, Fan1 has permanent power but now gets ground through Relay3. This makes them into separate parallel circuits and each runs at high speed. But this setup means you need two separate double-pole throws to put in an override switch. One throw needs to connect A-B and disconnect B-C, the other needs to connect X-Y and disconnect X-Z. Doable, but pretty complicated.

However, that may be the only option. I was thinking perhaps the output from the A/C pressure sensor could be tinkered to make the ECM think the pressure was "high but not excessive", since the fan kicks on high above about 220 psi but doesn't force compressor shutdown until above 300. The problem is, the compressor is a swash plate type and that would also make the IPDM dial back the swash, greatly reducing your A/C output. So the tranny would cool down but you might swelter. Tinkering the engine temp reading is also possible, but that will screw up the gauge reading and maybe cause the ECM to declare an overheat when it isn't really hot. Aargh. Go ahead, ask me why I hate all this integration!

I'll keep thinking about it, maybe something better will come to me.

Aargh!
Sorry, duh, I have no idea why this didn't occur to me sooner. I had the same issue with the wife's Altie. There's a thermostat for the beehive and I bet yours is stuck.

Try pinching one of the beehive coolant lines off with a hemostat or small C-clamp and see if your temperature problem improves. If it does then the 'stat is probably causing your issue.

OK! spouseman out of town, will try when he gets home (he loves small spaces!) Thank you VStar!

VStar650CL wrote: ↑

Fri Sep 09, 2022 8:42 am

Aargh!
Sorry, duh, I have no idea why this didn't occur to me sooner. I had the same issue with the wife's Altie. There's a thermostat for the beehive and I bet yours is stuck.

Vstar - Is this a common issue? What's the failure symptoms? Just that the CVT runs hotter? Do you see this across all models?

It made the wife's car run about 20F hotter than it should have. It's a hard-to-check condition, so I'm frankly unsure how prevalent it is. From what I've discovered lately about ventilation in the Nissan van/SUV body styles, people who live in hot climates or routinely drive mountains might be better off putting a ball valve in the coolant lines to block the beehive entirely under most circumstances. Outlet tank temps on those body styles, especially your Quest, seem to run much higher than on sedans with the same powertrain. That would imply a generic ventilation issue, and since outlet tank temps govern how efficient the heat exchanger can be, that's bad news.

I'm thinking to modify an inline heater valve (like the A60 Titan heater shutoff) to respond to ambient air and engine temperature, which would cut off beehive flow at ambient temps above 60F with a warm engine. Dunno what it would cost, but let's say under $100 plus the cost of a heater valve. You'd t-tap the existing ECT sensor and "teach" the unit the warm-engine signal. The ambient sensor would locate next to your existing one. Let me see a show of hands about who's interested. If I hear from 5 takers, I'll design and build it.

VStar650CL wrote: ↑

Sat Sep 10, 2022 5:22 am

It made the wife's car run about 20F hotter than it should have. It's a hard-to-check condition, so I'm frankly unsure how prevalent it is. From what I've discovered lately about ventilation in the Nissan van/SUV body styles, people who live in hot climates or routinely drive mountains might be better off putting a ball valve in the coolant lines to block the beehive entirely under most circumstances. Outlet tank temps on those body styles, especially your Quest, seem to run much higher than on sedans with the same powertrain. That would imply a generic ventilation issue, and since outlet tank temps govern how efficient the heat exchanger can be, that's bad news.

I'm thinking to modify an inline heater valve (like the A60 Titan heater shutoff) to respond to ambient air and engine temperature, which would cut off beehive flow at ambient temps above 60F with a warm engine. Dunno what it would cost, but let's say under $100 plus the cost of a heater valve. You'd t-tap the existing ECT sensor and "teach" the unit the warm-engine signal. The ambient sensor would locate next to your existing one. Let me see a show of hands about who's interested. If I hear from 5 takers, I'll design and build it.

I'm in my friend

VStar650CL wrote: ↑

Fri Sep 09, 2022 8:52 am

Try pinching one of the beehive coolant lines off with a hemostat or small C-clamp and see if your temperature problem improves. If it does then the 'stat is probably causing your issue.

I can't just hit that CVT heater thermostat with a hammer a couple of times?? (wink wink)

Just a clarification pls...you mean to C-clamp one of the original lines from the beehive and NOT one of the new lines that now goes to my new Hayden, right?

Yes, one of the coolant lines (fat ones), not a transmission fluid line (skinny ones). You want to pinch off coolant flow to the hive so it can no longer warm the tranny fluid.

Okay, I decided to do this a little bit differently. I found out the Widget Man gauge trimmer circuit board already has everything needed to make a full thermostatic cutoff, so I'm going to pirate a few of their boards for prototypes. I found a nice, reasonably small solenoid with Viton seals that can replace the Nissan CVT thermostat...
https://ussolid.com/u-s-solid-electric- ... -seal.html
...and is normally-closed, so its failsafe mode will be to keep the tranny cold. Then a Ford Ranger/Mazda B4000 ECT sensor in a brass tee will directly monitor the CVT fluid temperature at the beehive outlet...
https://www.carid.com/maneki/coolant-te ... r020s.html
...acting to cut off the beehive above 165F fluid temperature. I'm going to use the wife's Altie for a guinea pig, and assuming it works well, I'll let everyone know and probably offer a kit.

VStar650CL wrote: ↑

Sun Sep 11, 2022 10:53 am

Okay, I decided to do this a little bit differently. I found out the Widget Man gauge trimmer circuit board already has everything needed to make a full thermostatic cutoff, so I'm going to pirate a few of their boards for prototypes. I found a nice, reasonably small solenoid with Viton seals that can replace the Nissan CVT thermostat...
https://ussolid.com/u-s-solid-electric- ... -seal.html
...and is normally-closed, so its failsafe mode will be to keep the tranny cold. Then a Ford Ranger/Mazda B4000 ECT sensor in a brass tee will directly monitor the CVT fluid temperature at the beehive outlet...
https://www.carid.com/maneki/coolant-te ... r020s.html
...acting to cut off the beehive above 165F fluid temperature. I'm going to use the wife's Altie for a guinea pig, and assuming it works well, I'll let everyone know and probably offer a kit.

Hey VStar - Found this in the specs for the above solenoid valve:
"OVERHEATING WARNING: Not designed for continuous operation(not a 100% duty cycle). While energized, under normal operating conditions, solenoid valve will get HOT. The coil will reach a maximum temperature of about 176°F (80℃), which is fully complied with national standard: JB/T7352-2010. If energized continuously for more than 8 hours the coil may burn."

Maybe a motorized ball valve might be better? Like this:
https://www.amazon.com/Motorized-Valve- ... 136&sr=8-1

Max coolant temp for this ball valve is 100C, but I've seen others with higher media flow temps. Just a thought...

Paul

No, I'm building PWM into the solenoid. I don't like the notion that a ball valve can stick wide open if there's a system failure, then it's no better than the idiot OE thermostat. That's why, on further thought, I rejected the A60 valve as well. An NC solenoid is failsafe cold, and that's critically important. I just need to get an actual valve to determine what PWM level will hold the valve open once it lifts, that depends on the coil and shuttle characteristics and can only be determined empirically when the OE doesn't specify it (which in this case they don't). Trust me on this one, I did a lot of solenoid PWMing on farm equipment in my last life. It will work fine.

PS - It will also have a second low-current output (200mA) which can drive an LED warning lamp or a relay for an auxiliary fan or motorized diverter valve. I'm thinking to have that kick in at 195F. Thoughts?

VStar650CL wrote: ↑

Mon Sep 12, 2022 6:37 am

PS - It will also have a second low-current output (200mA) which can drive an LED warning lamp or a relay for an auxiliary fan or motorized diverter valve. I'm thinking to have that kick in at 195F. Thoughts?

I get it. I defer to your experience with solenoid valves, but if the valve is energized it will create heat. I just thought a ball valve might be better because it is not energized in either position - only when it's activated.

Also - Please define "PWM"?

And isn't the purpose of the OEM beehive Tsat to remain open below a set temp (165F?) and close above it? The point is to prevent hot coolant from circulating through the beehive at higher ambient temps, right? Looks to me like they just engineered the cheapest solution. I like your idea...

PWM is "pulse width modulation", you basically switch the power on and off very quickly so that it looks to the subject device like a variable voltage. I'll probably go with something around 1 KHz frequency for this device. The amount of "on" versus "off" time in the signal determines how high or low the voltage looks to the coil. With solenoids, the mag flux to keep the valve lifted is always much less than the flux required to pull it in initially, especially if you add a freewheeling diode which slows down the collapse of the magnetic field. Generally 30~40% power will keep most solenoids happy. So the idea is to only give it full current long enough to lift it (usually a second or two) and then begin pulsing the power at a lower level.

The one thing I absolutely want to avoid in this system is any possibility of the valve sticking open because of a power failure. That can happen with any motorized valve. The solenoid is spring-returned, so if the power drops out the solenoid will close. It still isn't 100% failsafe because the driver FET could melt and lock the solenoid on, but the potential for damage would be limited to the 8 hours or so it would take the coil to fail. That's an acceptable failure mode, unlike sticking open.

You're quite right about the operating principle, but what will be different from the OE system is that the feedback will be direct. The beehive 'stat governs the temperature based on how hot or cool the coolant exiting the hive is, basically an indirect measurement of how much heat was soaked off by the tranny fluid inside the hive. You don't need rocket science to see why that's a crappy way to do things. This device will actually measure fluid temp and not need to rely on inferred temperature values.

For those who might be interested in the process of developing a gadget, here's the schematic and preliminary code. I decided to create actual proto boards instead of pirating the WM boards, they're on the way along with the other needed hardware. When it all arrives, first step will be assure the heat profile for the solenoid.

Cool project VStar. Never knew a CVT oil heater was a thing.

Well, so far so good. Solenoid has been running at 9KHz / 54% off a NAND test oscillator for about 2 hours and it's basically a handwarmer. I don't have my IR shooter at home but I can hold the coil retainer nut (hottest part) for about 20 seconds and the coil body indefinitely, which puts the temps around 45C / 35C respectively. I'll let it run overnight and IR it tomorrow after work, but right now I'd say coil temperature looks like a non-issue. The solenoid itself is quite strong at 54%, so I think dialing the frequency up and duty down won't be a problem either. Looking like this valve is a go!

Nice!

Data is in and it's excellent. Turns out the finger gauge was pretty accurate, it feels somewhat warmer after 20 hours run time and the IR confirms it, 44C body, 54C retainer nut. Given that the solenoid will basically be right in the radiator fan outflow (where the beehive thermostat is now) and have plenty of ventilation, I don't foresee any heat issues. The proto circuit boards should arrive this afternoon and the rest of the hardware by Friday, so very shortly this will be game on.

Proto PCB's stuffed and programmed. Let the tests begin!