Cruise control and the vehicle dynamic control system

The Gas and Diesel Engines - VQ40De, VK56DE, YD25DDTi, V9X, Transmission, Transfer Case, Oil, Differentials, Axles, Exhaust...

Moderator: volvite

Marc89GTi
Posts: 17
Joined: Thu Jun 21, 2007 10:22 pm
Location: Prince George, BC, Canada

Cruise control and the vehicle dynamic control system

Postby Marc89GTi » Fri Nov 16, 2007 2:36 pm

When we first got our 07 Pathfinder LE when using the cruise on the highway anytime going down a big hill it would maintain the set speed. You could feel it applying the brakes to maintain that speed. Recently when using the cruise control it hasn't been doing this.

Was just curious what most of you have observed while using the cruise control and going down hills.

And the other night it was snowing here and the roads where quite slippery. I pulled out of a parking lot onto a road where there was a small hill, I had it in auto 4wd mode, gave it alot of gas, the back end started to swing out so I steered into the skid, when caused the truck to spin and do a 180 turn. I didn't feel the brake pedal pulsate and the steering wheel was easy to turn when I was turning into the skid. I didn't notice the slip light come on. The only time I can get the slip light to come on is when I leave it in 2wd mode and gun it on some ice.

I'm starting to wonder if the VDC system is working properly. When I pull away from a red light when its slippery I can feel the front trying to pull to one side. This happens when accel faster than I probably should, but I've been trying to see what this vehicle can do in icy situations so I know how to deal with it in an emergency situation properly.

Maybe some of you guys have played in snow and can let me know your experiences.


User avatar
RacerZX
Site Admin
Posts: 869
Joined: Wed Jun 14, 2006 10:00 am
Location: Silicon Valley, CA
Contact:

Postby RacerZX » Fri Nov 16, 2007 6:47 pm

The cruise doesn't apply the brakes, but it will downshift sometimes. It's not consistent, I haven't figured out when it decides to do that and when it doesn't...

As for the VDC, maybe because you were in auto-4wd the truck sent power to the front wheels just when you were counter steering causing you to overcorrect and spin? Try to find an empty parking lot and play, no better way to learn how it'll respond...

Marc89GTi
Posts: 17
Joined: Thu Jun 21, 2007 10:22 pm
Location: Prince George, BC, Canada

Postby Marc89GTi » Fri Nov 16, 2007 6:57 pm

I have found that applying the brakes going down hill a couple of times or so will cause the transmission to downshift, thus thinking that you don't want to go any faster down the hill.

In the summer time I have found that when this happens and I put my foot back onto the gas nice and easy the transmission will rev up even though you would think that it would want to up shift because your no longer wanting that gear, but when it does shift, the shift is a bit rough, especially if you blip the throttle.

The service manager at one of the dealers said this is normal and can be caused by a high temperature in the transmission, it tries to prolong the shift so that the transmission can cool down (more fluid circulating) and thus the hard shift.

But it terms of going down hills, the cruise would maintain a very tight speed control of the set cruise speed. That would make sense that its just using the transmission to make the vehicle slow down.

boogyman
Posts: 519
Joined: Tue Jul 04, 2006 6:04 am
Location: Jersey

Postby boogyman » Mon Nov 19, 2007 10:51 am

It sounds like the truck wasn't in 4wd but in auto when you went around the corner. The front wheels should have been pulling and preventing you from having the backend slip out. It should have been in 4wd hi. Auto doesn't kick in till it senses slip. Although it should have before the backend started coming around on you. That is why there wasn't tension on the steering wheel. You can definitely tell the difference when 4wd is active.

Marc89GTi
Posts: 17
Joined: Thu Jun 21, 2007 10:22 pm
Location: Prince George, BC, Canada

Postby Marc89GTi » Mon Nov 19, 2007 9:15 pm

It was in auto mode when the back end kicked out on me. The roads that night were extremely slippery.

I did some playing yesterday in an empty parking lot. I left the truck in auto mode, accelerated then turned the left then the right. The vdc was applying the brakes the appropriate wheel was able to stabilize the vehicle. I did notice however it will let you do a power slide when turning around, this only happened when I was turning around to head in the opposite direction. I think the vdc looks at the steering angle so probably knew that I was turning around. It's pretty neat the was that it works. The bottom line is that the all seasons won't help you at if you have 0 traction. Next year I think I will get some Nokian winter tires.

I was reading in the shop manual and I can't see anything that talks about maintaining vehicle speed while going down a hill and using the cruise control. Just curious about others experience with cruise and going down big hills.

User avatar
RacerZX
Site Admin
Posts: 869
Joined: Wed Jun 14, 2006 10:00 am
Location: Silicon Valley, CA
Contact:

Postby RacerZX » Mon Nov 19, 2007 9:56 pm

I played a bit with the latter today, and it appears that it'll do it even if not on cruise, just be going down hill at least 45-50MPH, apply the brakes gently and let them off again and it'll downshift to 4th from 5th by it's self to try and maintain speed.

User avatar
ralphwiggums
Posts: 59
Joined: Mon Jan 08, 2007 12:05 am
Location: vancouver BC

Postby ralphwiggums » Thu Nov 22, 2007 2:34 pm

RacerZX wrote:I played a bit with the latter today, and it appears that it'll do it even if not on cruise, just be going down hill at least 45-50MPH, apply the brakes gently and let them off again and it'll downshift to 4th from 5th by it's self to try and maintain speed.
i've found this to be the case too. I do have a big complaint on the way Nissan programmed the transmission to pick when it shifts up or down. it always seems to be either in too high or too low a gear for me - i REALLY wish I had a manual transmission.


Return to “R51 Engine, Driveline and Powertrain”