[S_P_Y]

I posted in another thread but I haven't heard back from anyone so I thought I would start another discussion to see if anyone else has had this issue and see if there was a resolution.

I have a 2017 Pro 4x diesel and have had this issue twice already. I am taking it into the dealership 7/9/2020 and I'm sure they won't be able to recreate this condition so I'm looking for areas to push them towards.

Local Temp was in the 70's at about 10,xxx foot of elevation. I was on a trail with about an 8% grade, in 4 low and the RPM's wouldn't come up even when floored. It was a rocky trail but I wasn't losing traction the RPM's just wouldn't rise.

I had to turn off the A/C compressor, back up to the flat ground to be able to rev the RPM's, and gun it to make it up. I saw someone mention the possible issue is the ECM?

Has anyone else experienced this before? Were you able to find a resolution?

Thanks for all the relevant advice.

 

[RoadLessTraveled]

I think in the past this type of problem was traced back to traction control/vehicle dynamic control intervention. You may not feel the traction slipping but the sensors detect something and based on the attitude of the vehicle and everything else it starts limiting power. If you try the same maneuver with VDC/Traction Control turned off I bet you'll have more power.



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[S_P_Y]

I think in the past this type of problem was traced back to traction control/vehicle dynamic control intervention. You may not feel the traction slipping but the sensors detect something and based on the attitude of the vehicle and everything else it starts limiting power. If you try the same maneuver with VDC/Traction Control turned off I bet you'll have more power.



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Thanks for the information! That didn't even cross my mind.

 

[Jayce]

I thought traction control turned off automatically when 4wd was switched on?

 

[QuikCoastie17]

I thought traction control turned off automatically when 4wd was switched on?

nope.

 

[huZZah]

Nah cause some scenarios the TCS actually helps you climb obstacles without gunning it. Then I would think that heavy diesel engine would help as well.

And I actually keep mine on when pulling boat out if the water. It really helps if you leave it in and ease the gas in 4wd. Like, it’s easier around lakes here where the ramps are always muddy/mucky and shallow so you’re dragging your back end in the water. Guys always say turn it off but they are flooring it and slip around.

 

[S_P_Y]

*Update

This happened again. I didn't try to turn off the traction control because I honestly forgot to test it.

However, I did notice the trans temp shot up. I let it cool for about 20 min on the side of a trail. As I resumed and the trans temp jumped back up, it happened again. This happened a total of 4 times on a single trail.

I'm at the dealership now doing a trans flush to see if there is an issue. I was told there isn't a sensor in the trans that will put the truck in creep mode.

Has anyone else seen their truck respond like this to give me another direction to look in case the fluid change doesn't work? Thanks!

 

[RoadLessTraveled]

[QUOTE="S_P_Y, post: 548021,

... trans temp shot up. I let it cool for about 20 min on the side of a trail...

....I was told there isn't a sensor in the trans that will put the truck in creep mode.....

Has anyone else seen their truck respond like this to give me another direction to look in case the fluid change doesn't work? Thanks![/QUOTE]


I cannot speak to the possibility of there being a problem with your transmission or cooling system.

These are big heavy trucks & I don't think they are well suited for rock crawling & grinding long periods of time at slow speeds on difficult trails, it could just be that you are asking more of it than Nissan originally designed it for? (I'm not saying I don't think they should have considered that type of use, just that they didn't design for it)

I can say that there most certainly IS a temperature sensor for the transmission (note: we actually have gauges showing that although they aren't fantastically accurate) and the truck's system most certainly WILL detect an overheating situation & put the truck into a type of limp mode.

 

[phlfly]

Next time watch your transmission temp.

 

[JBouy]

I have experienced a similar situation. And it was the transmission temp that caused the de-rate.

I experienced it recently while pulling my boat (7k lbs) up an 8-10% grade with 8-9 people in the truck cab/bed from a near stop (coming out of a hair-pin corner). Probably overloaded a bit based on payload, but it was in a campground and the speeds were 20mph max. Usually, when I hit the hair-pins I manually shift into 1st to control the shift point coming out of the turn, but forgot this time. When the truck decided to shift into second the RPMs raced for a bit while trying to lock up the torque converter. It seems that if the torque converter does not lock up quickly, like within a few seconds, the trans temp starts to climb very quickly. Which is what happened. And I lost power as the truck de-rated to protect the transmission.

I stopped in the middle of the hill climb, put it in neutral, and revved the engine to about 1200 RPM to cool the transmission. After the temp gauge (bar) reduced to the half-way point, I shifted into 1st and off we went with no additional issues.

What appears to be happening to me is that the torque converter does not fully lock up at certain loads/speeds which causes a lot of slippage. This heats the fluid very quickly and the cooler cannot keep up.

Your problem description does not state if you are in "drive" or if you manually shift the truck your situation, but I would recommend manually shifting to keep the RPMs up and making sure the torque converter is fully locked up.

 

[S_P_Y]

@JBouy Thanks, it's sounding like I may need to add a secondary trans cooler then. You're the first person to have noticed this. Now that you mention it, these are tight turns and I'll try switching to manual to see if that resolves anything.

@RoadLessTraveled The dealerships don't seem to know a lot about diesel Pro4X in general. So, I wouldn't be surprised if the temp sensor does control an RPM creep mode. Do you know for a fact there is a temp sensor to place it in a creep mode? I'm trying to isolate any potential issues. Should there be, it's confirming a secondary trans cooler maybe my best go-to.
Very few trucks are factory designed for trails that I do, so the goal is to improve the truck so it is capable. The problem is, knowing what to improve because there isn't a ton of documentation for them.

 

[JBouy]

I do not know, nor do I think, there is a sensor to control RPM creep mode specifically; the ECM is trying to protect the transmission from cooking itself. There is a temp sensor for the transmission and for the torque converter. If the temperature gets too high, the ECM de-rates to engine to protect the transmission. I have seen these PIDs and actual temperatures when using the auto agent app with EZ Lynk, so they are there even if most OBD 2 scan/read tools do not "see" them (I've tried 2 others - Blue Driver and OBD LX - and they do not have trans temp or torque converter temp).

I would suggest before investing in a secondary trans cooler, try the trails manually shifting and see if the problem occurs. Based on your description, I am guessing these are low speed trails. I would start in 1st and not up-shift until RPMs are above 2500. If it feels/sounds like the trans is not locking up within a second or two, shift back down. Tow mode may also help as it moves the shift points to a higher RPM

 

[phlfly]

Yes it's great idea i do off road I keep low and 2 second and or third gear all time . But I noticed on H it will overheat