Cruise control drops speed when activated - is this common?

[5logs Junior Member Find all posts View Profile Close 5logs]

This gets a bit more interesting as driving around today I have confirmed it drops speed even after 'holding' the speed with the accelerator for a while - after locking it in using the cruise control. But the kicker for the day is it appears there is a definite fault as it has now twice dropped out of its selected speed completely on the same right hand slipway turn from one freeway onto another at close to 100kph.

Interesting my cruise has dropped out twice in the same location also, a left hand turn with a slight bump in the middle, wonder if the stability control is kicking it off, as a very early intervention measure.

[RB80 Junior Member Find all posts View Profile Close RB80]

According to toyota service mgr it is a safety measure when the sensor reads too much roll plus other computery things he didnt elaborate on. Mine was doing way more with slightly larger tyres, presume more body roll and higher cg. Ecu calibration and it is back to normal.

[odarprado Lurker Find all posts View Profile Close odarprado]

5logs, I think you are correct in that it seems to be related to the stability control in some way - I've now been able to replicate it on a right and a left hand turn at speed - no need for bumps - it just seems to dislike the rather modest 'G' forces.
RB80 - Yes to your first point, ie it drops the 'Set' icon and cruise speed is lost. Re your second comment - did you have Toyota recalibrate your ECU? If you did - did that get rid of the dropping out on corners (the roll issue) and the losing speed when you engage it? (Or didn't you have the losing speed issue?)
I was seeking to turn the traction control off to test it without that doing it's thing - but it seems to re-engage automatically when you exceed 60kph, it the light saying it is off goes out. So no ability to prove any more there at the moment.

[Gordon Member Find all posts View Profile Close Gordon]

Eau de Prado you might be just disengaging TC when you need to switch off VSC to test this theory. Assume it's the same in the 2.8 but on the 3.0 to disengage stability, I have to press and hold the VSC button til VSC illuminates. Maybe that won't automatically re-engage...

[RB80 Junior Member Find all posts View Profile Close RB80]

Odarprado, yes by toyota. I had a thread incorrectly titled something like "power steering cuts out mid corner" where i went into a bit. Was free at the dealer, fwiw.

Edit: cruise is still slow to engage

[K & M McF Senior Member Find all posts View Profile Close K & M McF]

My Prado 90 series locks immediately on the speed when it is set. My wife's Suburu Forester is the same. Over the past 10 days we drove a Nissan Patrol in the Northern Territory and it behaves like the OP's 150 series. I have also driven a number of other vehicles that do the same.

[odarprado Lurker Find all posts View Profile Close odarprado]

Ok. Gordon - you are of course correct - flicking the switch just kills of the Traction Control - to get rid of TC and VSC you need to hold the button for 3 seconds (amazing what you learn when you read the manual) - and then your cruise control won't work at all until you restart the car and TC and VSC are again enabled.
RB80 - thanks for your response - may come in handy in future interaction with the dealer. I had the first inspection done today and told them about the cruise control issues and they took it for a test drive but couldn't identify it. This makes some sense as the local highway is limited to 80kph and at that speed the difference is about 1 point something kph that it loses. So I'm now booked in to test drive it with one of their technicians in a couple of weeks to demonstrate the problem.
K&M McF thanks for your comment I have driven a number of vehicles and they all seem to have accurate cruise controls - as did my Prado 90 - so to me it's a fault - especially when the owners manual states the cruise control will lock in the speed it is set at. RB80's comments are encouraging - as I would expect they can fine tune it - if they know how to and can be encouraged to do so.

[odarprado Lurker Find all posts View Profile Close odarprado]

I took a Toyota technician for a test drive last Monday and demonstrated the two issues, ie:

1. Cruise control on, required speed selected, speed drops (typically 1-2kph) and then slowly increases until it regains the selected speed
2. Cruise control on, required speed selected turn longish corner (think open sweeping bend at 60kph plus), selected speed drops out (cruise control still activated)

The Toyota technician was a lovely Japanese gentleman who I was having some difficulty understanding - but he did his best to explain that he felt '1.' was due to the vehicle being a manual and that was just the way they behaved. (I struggle to believe that given my old 95 series never behaved that way - it had cruise control that just worked the way it should.) For '2.' he went off and did some homework and advised that the cruise control computer is linked to the traction and stability control computer and that they are collectively set to cancel the set cruise control speed when the steering wheel turns past 45 degrees from straight ahead. (I can believe that is what is happening - but disagree that it should work that way. This appears to be a recent/current model thing as an assertive test drive of an earlier 150 series (manual D4D) identified you would have to put it on it's side before the cruise control would cancel out.)

Anyway - at the end of all that we agreed he would reset the parameters of the cruise control - back to baseline and off I would go and see if that made any difference. It appears to have slightly reduced the drop in speed that occurs when the cruise control is activated - but I could be imagining that. There is no ready ability to adjust any of the factors that are driving the issues stated here in the TechStream diagnostic software they have.

Overall - I'm not sure what to do next - I will probably at least seek to escalate this with Toyota because I don't think either issue is acceptable - a cruise control should readily and accurately lock in the selected speed - and the 45 degrees off-centre simply shouldn't happen in my opinion - or it should be more intelligently linked to the traction/stability control so that it is dropping out if the vehicle is really and truly losing traction - not simply cornering at a decent speed.

I suspect this may all land in the too hard basket - but I'll plug away for a little longer.....

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

Both my 90 & 120 hold the speed as set however the new triton at work does the same stupid drop 5kmh and then ramp up again. Probably wouldn't have cared but after reading this thread it is now more noticeable.

[yowie Advanced Member Find all posts View Profile Close yowie]

My petrol auto 150 kicks back rather hard.

If it is set on say, 100, will cruise along fairly easily. Heading up a hill, the speed will drop to about 90, then the auto will kick back into 2nd and take off, maybe move to 3rd, but keep accelerating until over the top of the hill, when the speed will hit 120 to 130, before slowing back to 100. I have to disengage the cruise before heading up some hills.

When I was working and driving Commodores, Falcons and Magnas, none of them had such extremes in their cruise control operation.



As for the cruise control dis-engaging when the steering wheel is turned at a sharp angle, it may have something to do with changes engineered due to older drivers having a medical issue, with the cruise engaged, and not being able to control/stop/steer the vehicle which will become an out-of-control missile.

[RB80 Junior Member Find all posts View Profile Close RB80]

The cruise dropping out is a safety thing, when the car senses the body roll etc warrants more driver input.

I don't think it's 45deg though, and far more complex sensors than steering wheel angle. When it was first exhibiting the symptoms after the 265/70 tyres I could be driving at 60 and with a quick/firm tug on the wheel it would disengage it. The angle of the wheel would be less than 6in of wheel movement, but sufficient to upset the car and disengage the cruise. & that's driving in a straight line, at 50 or 60, tug the wheel firmly & let the tech observe the cruise light now disengaged. He was surprised but seeing is believing.

OP my slow cruise engagement is on an auto, not manual. So your guy is 2 for 2 wrong I'm afraid.

[Gordon Member Find all posts View Profile Close Gordon]

I don't think it's 45deg though, and far more complex sensors than steering wheel angle. When it was first exhibiting the symptoms after the 265/70 tyres I could be driving at 60 and with a quick/firm tug on the wheel it would disengage it. The angle of the wheel would be less than 6in of wheel movement

6" of wheel movement is closer to 90 degrees than 45, and after experiencing OP's issue first hand i can say it feels more like a SAS response than body roll or yaw (which are really minimal during this manoevre). It's not a savage yank on the wheel at all. For what's it's worth I wish RB80 was right, cos I would appreciate cruise being switched off by an unstable car, but a 45 degree turn of the wheel with no hint of instability is a bit boring. Maybe in the 180 series....