Van Jackknife

Submitted: Thursday, Oct 09, 2008 at 00:15
ThreadID: 62388 Views:4630 Replies:11 FollowUps:13
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Just purchased New GX Prado with opt pack 2. When towing 20' van downhill (not far out of Tamworth heading towards Armidale for those interested) I entered a long left hander only to hear the dash sound a warning beep then appear to near lock up rh front wheel or loose traction on rear wheels which ever. This in turn jacknifed the van and by luck more than anything else we sraightened up some 30 meters later. Scariest crap I have had to deal with in my 31 years of driving. The beep I believe was the "slip indicator light" but not sure as I had my handfull keeping the car and van on the road at the time. The brakes would have been pretty warm at the time also. Although I feel nearly 99% that I had finished braking and was simply cornering at the time. I can only assume it had something to do with the "active traction control system" Can you advise me if van pushing from behind would compromise the system?

Sent above enquiry off to Toyota and was told to take vehicle off to dealer for inspection. I responded with below email in mid August and still awaiting response.

Thank you for your suggestion

I had the vehicle inspected by a Toyota dealership just after occurrence (as you would having nearly wiped out me and my family) but of course nothing abnormal detected. And there has been nothing wrong when driving the vehicle normally. The problem only occurs whilst towing caravan downhill. There has been 2 occasions where there has been a warning beep and because I have been cornering it has been difficult to avert me eyes to the dash to see what’s illuminated. One of these occasions it appeared to be the "slip indicator light". And the other time I didn’t get a chance to see any warning lights (this was the incident where it appeared as if major traction was applied to the RH front wheel, this in turn jackknifed the van).

After the vehicle inspection by Toyota I asked if any of these “driver assist” functions could be disabled.
After looking for switches on the dash and console the reply was “no”. It appears to me that the only time that any functions of this nature can be disabled is when you switch over to engage the centre diff lock. Is this correct?

Have you any explanation to what may have occurred in the van jackknifing incident outlined in my initial email and what actions could be taken to avoid such a situation again? I know this is a big call but nobody has been able to explain to me exactly how active traction works under certain circumstances i.e. when vehicle is getting pushed on an angle from behind by a caravan. I must at this point mention that I am only assuming the “active traction” somehow kicked in or ceased thus causing the situation.
And what possible combinations a warning beep from dash indicates. Just as a reminder it is a 2008 GX Prado turbo diesel auto with option pack 2.

As you can understand I don’t take this incident lightly as it had the potential to be a fatality for both my family and any other oncoming vehicle occupants at the time. Any comments will be viewed with great interest.

End of Toyota correspondence.

I am also currently seeking feedback from various avenues including Insurance Companies . I remember when I sat down with the Toyota sales rep he told me of a nice retired Italian couple who had just been in the previous week after rolling and totally their relatively new Prado and van. He said to them that there were two good things to come out of the ordeal. One being the air bags and seatbelts worked fine and injuries were minimal. The other being that their insurance cover meant they stepped into new car with more features and better economy. Now at the time I thought that being old retirees they may be new to towing so I put it down to inexperience but after my episode I’m not so sure. Whilst up at Brunswick Heads our neighbour told me he had just come down from Cairns and saw a similar accident and heard of another within the following week. (Tow vehicles not specified) Now don’t get me wrong I don’t feel it’s common to the Prado but in my case it was definitely “vehicle stability control system” which brought upon my near accident. And as near as I can make out the “traction control” must have been the culprit

Sorry explanation is so long. Has anyone heard of any similar incidents and anyway you can disable all this rubbish for towing conditions only? (never had this grief when towing same van with the 1991 fairlane)

Thanks
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Reply By: Motherhen - Thursday, Oct 09, 2008 at 01:11

Thursday, Oct 09, 2008 at 01:11
Sure is scary. What is the weight of the van and the weight of the vehicle? I am not familiar with vehicles that give audible warnings, and have done only very limited driving not towing in ones with traction control, so cannot help you as to why this occurred.

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Follow Up By: Jayko - Monday, Oct 13, 2008 at 22:08

Monday, Oct 13, 2008 at 22:08
Van is 1630 kg and car 2900 kg. Have not taken over weighbridge so unsure what it comes to when loaded. I don't cart water in van when towing and we travel relatively light. Two adults one child.
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Reply By: _gmd_pps - Thursday, Oct 09, 2008 at 02:23

Thursday, Oct 09, 2008 at 02:23
If you brake and the trailer brakes are tighter and uneven than the vehicle this can happen. the Prado is relatively light and if your trailer has uneven brakes (one side more than the other) this happens. I don't think its the car (other than it being light) .. more likely to be the trailer. The whole experience might have been increased by traction control but most likely not caused.
Generally I find peoples car choices questionable. 90% are unsuitable for the load towing. You need to have a safety margin in the combo and in most cases (even CTs) that safety margin is non existent or even negative. I would check the trailer brakes on a test stand.
Good luck
gmd
AnswerID: 329002

Follow Up By: Jayko - Monday, Oct 13, 2008 at 22:29

Monday, Oct 13, 2008 at 22:29
Your advice makes sense and I can see that happening. I feel that I had well and truly finished braking and was 3/4 of the way around the bend, yes a little faster than I would have liked but didn't have that unnerving feeling about the speed at the time. I am aware that LHF wheel on van is braking a tad more than the other three but have not got around to adjusting. I will do so before next trip. Had the brakes on the van adjusted via the Hayman Reese controller very weak at the time of the incident and have cranked them up a little since. I know I said the van to be 20' but it is sold as 17 1/2' so I was going by the external measurements. Car rated to tow 2500 kg and unloaded van comes in at 1630 kg I should take it over weighbridge some time when we are all loaded up.
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Reply By: Member - Russnic [NZ] - Thursday, Oct 09, 2008 at 06:33

Thursday, Oct 09, 2008 at 06:33
Hi Jayco
A bit scary when that happens. Seen a wreck or two with trailers jack knifing, worst case while towing horses up through Burkes Pass in the Mackenzie country, a woman had a 20 foot or so van tied on the back of Nissan Fairlady, the van took over on the last sweeping bend. "Wreck"
The tow vehicle was totally unsuitable for the task required.
A few questions.
Weight of tug / trailer ratio?
Why were the brakes pretty warm? I presume the tow vehicle is an automatic, does it hold down in the shifts, had you selected a low enough shift down to avoid the brakes heating?. If the tow vehicle brakes were pretty warm perhaps the van brakes were even warmer and had stopped working.
Had you braked before the bend and did you accelerate out through the bend..
My F250 truck, auto has a tow/haul mode, i was a little sceptical at first, not now, came down through Arthurs Pass with my 30 ft 5er on, only touched the brake pedal coming into a few corners, the auto down shifted as required, I don't think I would have done much different driving a manual. I do set the trailer brakes so you can just feel them come on before the truck brakes.
Good luck
Cheers
Russ
AnswerID: 329007

Follow Up By: Jayko - Monday, Oct 13, 2008 at 22:56

Monday, Oct 13, 2008 at 22:56
Van is 1630 kg and car 2900 kg. Have not taken over weighbridge so unsure what it comes to when loaded. I don't cart water in van when towing and we travel relatively light. Two adult’s one child. Mentioned that brakes would have been warm because I thought I recalled in the owner's manual that heated brakes may cause problem with the traction control system. On further investigating I see that it is the "brake actuator" getting too warm which can cause the "active traction control" to stop working. So in answer to your question yes the brakes would have been warm but not too warm. Yes auto in car. Had I had the time over I would have cogged it back one more gear. Had braked coming in to the bend but was simply cornering at the time had not touched the accelerator pedal.
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Reply By: Member - Tessa (NSW) - Thursday, Oct 09, 2008 at 07:53

Thursday, Oct 09, 2008 at 07:53
Jayko
I have a 2000 model Prado Auto with Traction Control. I don't know, but assume that the system is the same. I have towed my CT and now caravan - both weighed about 1500kg loaded - for about 100,000k's. The vehicle has now done 164,000k's. The only time I have had a problem was when, out with the 4wd club and not towing, we came to a very loose gravelled, very long steep climb. I didn't engage the centre diff lock and after about a kilometre and a half of constant use of the traction control it overheated and the warning beeper came on. This was a continuous beep, beep, beep which stopped as soon as I stopped the vehicle. Waited about 5 minutes, engaged diff lock and no more beep. On reading the owners manual ( obviously an absolute last resort) I discovered that the beep sound is simply an indicator that the traction control has overheated and has turned itself OFF. Bearing in mind that the traction control operates by actvating the brake on a particular wheel under certain circumstances, and your statement that the brakes would have been pretty warm at the time I agree with what has been said above that your problem is more likely to be the tail wagging the dog.

tessa
AnswerID: 329015

Follow Up By: Member - Tessa (NSW) - Thursday, Oct 09, 2008 at 09:38

Thursday, Oct 09, 2008 at 09:38
Jayko
I don't know if this will help. But I just found this on american forum. It sounds somewhat similar to what you described.
slip indicator light

tessa
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Follow Up By: Member - Russnic [NZ] - Thursday, Oct 09, 2008 at 12:04

Thursday, Oct 09, 2008 at 12:04
Hi Tessa
Don't get confused with a centre diff lock and axle diff lock, the centre diff lock basically puts the vehicle into 4WD and does not lock front and rear diffs. Traction control brakes the slipping wheel slightly to even traction loss, engage centre lock and you have 4 wheels driving , much better.
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Follow Up By: Member - Tessa (NSW) - Thursday, Oct 09, 2008 at 18:38

Thursday, Oct 09, 2008 at 18:38
Russnic
no confusion thanks - the Prado is constant 4wd and the centre diff lock locks the drive ratio between the two axles. Takes some of the strain off the traction control.

tessa
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Reply By: Sacred Cow - Thursday, Oct 09, 2008 at 08:36

Thursday, Oct 09, 2008 at 08:36
Jayko,

We have a similar Prado/caravan rig and at the beginning I thought it was on the brink of instability. The questions I would be asking are:
Do you have a Hayman Reese weight distribution hitch?
Is it set up correctly?
Do you have a Hayman Reese dual-cam anti-sway device?
Have you got most of your payload in your caravan over the axles?
Have you added things on the A frame or rear of the caravan?

If the rig starts going unstable, use only the caravan brake over-ride switch.

Regards
Glenn

AnswerID: 329022

Follow Up By: Jayko - Monday, Oct 13, 2008 at 23:58

Monday, Oct 13, 2008 at 23:58
Yes I have Hayman Reese weight distribution hitch fitted
I feel it is set up correctly going by the instructions on their web site.
Don't have a Hayman Reese dual-cam anti-sway device will look into this.
Have got as much a physically possible over the axles?
Have not added things on the A frame or rear of the caravan. Have kept the boot at front of van free of heavy items. Can't remember ball weight but was well under the 250 kg (did the bathroom scales method)
Thanks
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Reply By: Robin Miller - Thursday, Oct 09, 2008 at 09:04

Thursday, Oct 09, 2008 at 09:04
Jeez Russ that would scare the hell out of me to.

I can't imagine sitting in front of a salesman selling
me the good points of their Prado/Van rollover.

I agree that you need to know and deserve a proper explanation from Toyota.

Its a bit of an emotional subject but the Prado has a relatively high centre of gravity, signicantly more than your 1991 fairlane.

The bottom line from my experience in heavy industry electronic
control systems is 2 points.

1/ In the vast majority of times the electronic systems will benefit the driver.
2/ There can be special circumstances in which they won't.

From your description it seems that to much back pressure from a van which may not have had enough of its own braking effort would have lightened the inside rear wheel.

The car doesn't know theres a van attached.

There's usually a threshold at which the sensors react.

For the car to have taken action - means it must have had an initiating input.

I presume it was dry bitumen so the above should not have been enough to have any wheel slip, and hence no need to apply the front brake to even the car out.

So It did something else, noting that the brakes were warm !

The only things I can think of (outside of a malfunction) to cause active intervention like that would be that car/van hadn't settled down thru the turn and that the van may have pushed then pulled on the trailer coupling.

Questions- were you well into the turn ?
Could you say if the car/van was stable at the time (not jerking) ?
I believe you felt that you had just finished braking, so were you accelerating (even lightly) ?
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Follow Up By: Jayko - Monday, Oct 13, 2008 at 23:31

Monday, Oct 13, 2008 at 23:31
Read your response with great interest given your experience with electronic control systems. Would love to know all the ins and outs with the vehicle stability, downhill assist, active traction control systems. Still not sure which part of the system kicked in to “help me out" of the perceived problem. Van fitted with Hayman Reese weight distribution bars. In relation to your questions:
The car and van appeared stable.
Had finished braking and was nearly all the way round what I would term as a long sweeping (not particularly tight) bend.
Had not accelerated and was still in a decline. Road dry at the time.
I was going a tad faster than I would have liked but didn't have that unnerving feeling about the speed at the time. Did hear slight rubber squeal from front wheel about same time or just prior to dash warning beep. Not sure if this will help you come up with a likely explanation to what caused the initiating input you speak of.
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Follow Up By: Robin Miller - Tuesday, Oct 14, 2008 at 09:03

Tuesday, Oct 14, 2008 at 09:03
Hi Russ

We don't have a good working description of that particular control system , to see where it puts its emphasis first and no obvious answer comes to mind, but I think its worth pursuing.

Spoke also to another friend in same area and we both zeroed in on just what could have been the impertus.

A possibility is input from the van via the trailer coupling.

I.E. lets imagine an intermittant connection thru the trailer coupling that indicated brake action - this could definately initiate your front wheel snatch.

However for this to be a valid possibility the trailer connection would have to be shut that feedback could get back to the ECU and
we don't know this.

Along the same lines , even an intermittant or half on hand brake
that made a momentary connection could signal the ECU, but this
should normally be a low likelyhood event.







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Reply By: andoland - Thursday, Oct 09, 2008 at 09:27

Thursday, Oct 09, 2008 at 09:27
Just a thought, but is it worth checking that you don't have an electrical fault in the caravan wiring, brake controller or trailer plug that could be causing the issue with the Prado's traction control system?
AnswerID: 329031

Reply By: Nav 8 - Thursday, Oct 09, 2008 at 11:33

Thursday, Oct 09, 2008 at 11:33
Reading through your post I don't see any weights mentioned for your van. I have a 20 Ft full van and the only vehicle I can legally tow with is a vehicle with a minimum of 3000Kg towing capacity. I could be corrected here but your vehicle has a maximum towing capacity of 2500Kg. It maybe a case of the vehicle being too small for the job. Regards ...Nav.
AnswerID: 329046

Follow Up By: Member - Graham H (QLD) - Thursday, Oct 09, 2008 at 12:05

Thursday, Oct 09, 2008 at 12:05
Completely agree with Nav 8

Read this thread 61630 about a guy

who bought a van weighing 2600kg ATM
.
The salesman told him he could tow it with a Prado.

Dead wrong

A Get the van weighed with everything you take away in it.
B Look at the plate in the boot for the ATM weight.

If the answer to either A or B is over 2500kg be prepared to buy another vehicle to stay legal cos if it is more than that and you prang it " NO BINGO" no money from claim.

In reference to your original query about jacknifing.

It is usually caused by the tow vehicle pushing because its brakes arent workin or are coming on, too little too late or you drove down the hill in too high a gear and overheated everything.
The truckies anology of whatever gear u climb in use the same going down the other side is well worth following



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Reply By: Steve Ellis - Thursday, Oct 09, 2008 at 20:39

Thursday, Oct 09, 2008 at 20:39
I believe that the old principle of heavy tow vehicle towing lighter van should apply still. A few years ago they changed the rules so that we could tow a trailer that is heavier than the tow car if the manufacturer of the tow car said it was OK. How stupid was that? Now we have underweight and underpowered cars includig 4wd towing overweight caravans and trailers around the country. A recipe for disaster. The old rule said dont give a boy a mans job. They changed that rule and now we have problems. Is anyone really suprised?
AnswerID: 329123

Follow Up By: Nomadic Navara - Friday, Oct 10, 2008 at 15:10

Friday, Oct 10, 2008 at 15:10
The old van loaded maximum weight not exceeding the tare weight of the tug only applied in NSW(and per haps one or two other states.) Other states allowed you to tow 1.5 times the tugs tare weight. I do not know any manufacturer that rates the maximum tow weight of their vehicles at or near 1.5 times their tare weight. The result of the unified legislation is that in some states you can tow more than the old rules and some less.

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Reply By: awill4x4 - Thursday, Oct 09, 2008 at 23:15

Thursday, Oct 09, 2008 at 23:15
I'm assuming you are using a Hayman Reece WDH to level your van?
If so, you may be taking too much weight off the rear wheels, I found when I 1st started using the WDH that if I raised the back of the vehicle up to where it originally sat without the van I was actually taking too much weight off the rear and the van would push the rear of the car particularly going downhill around corners under brakes.
Using just one less link on the WDH gave the rear a little more weight and the van never pushed the rear of the car again.
Regards Andrew.
AnswerID: 329160

Reply By: Jayko - Thursday, Oct 09, 2008 at 23:41

Thursday, Oct 09, 2008 at 23:41
First up thanks to all your replies i will respond to all individually after i get back from short trip (4 days) close to home with the said van and Prado. Need some shut eye as i take off in morning.
AnswerID: 329167

Follow Up By: Gone Bush (WA) - Thursday, Oct 09, 2008 at 23:56

Thursday, Oct 09, 2008 at 23:56
Not sure about what sort of electronic stabilty controls are on the Prado, but on my 200 series I turn the Vehicle Stability Control OFF when towing.

It's programmed to stabilize the vehicle by itself, not the huge great pendulum of a van hanging off its butt.

I'm glad I ain't too scared to be lazy
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Follow Up By: Jayko - Monday, Oct 13, 2008 at 23:46

Monday, Oct 13, 2008 at 23:46
Would love to have the ability to turn it off on my rig, lucky you. The only way I can see that happening for me would be to pull a fuse but am sure that would send the computer into orbit and mean a trip to Toyota to have fuse put back in and system reset. Fuse controlling system involves disabling ABS, air con, power windows you name it.
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