Disabling The Vsc For Mot

[anchorman]

I was recently reminded by our good friend Fujisan that as some 4.3s will be due for the first MOT this year that it might be a good idea to review this subject and I will pin it for future use.

The VSC is such that if you use conventional means to test the brakes (brake roller tester with one wheel being tested at a time) it will pick that up as the vehicle out of control as one wheel is turning and three are not. The system cannot detect that the vehicle is stationary because there is a speed sensor on each wheel (used for vehicle speed detection rather than ABS operation - very unusual). The one turning wheel will fool the system into thinking that the vehicle is in motion. For this reason the VSC MUST be disabled otherwise when the first wheel turns in isolation from the others it will try to lock up the transmission in 4WD and the brake tester will force the wheel to turn against the locked transmission. Serious damage could result as you will be trying to haul a ton and a half of RAV out of the brake roller by one wheel against partially applied brakes because the tester is pressing the brake pedal!!! It is a potential RAV transmission/VSC infighting thing!

A main dealer should know what has to be done and will install his DLC3 tester and set it to "brake test" which will disable the VSC/Traction Control. However, I for one will not be going to the dealer for MOT (purely as a matter of convenience) and if anyone else has similar plans then the VSC has to be disabled. It is extremely risky to assume that the independent tester knows about this very unusual system and wouldn't just go ahead and test it in the normal way. There are three ways to ensure the test is conducted without risk. You personally don't have to do it yourself but it would be wise to print this out and take it to the MOT station and make sure they are very aware. Here are the three methods;

1. Use the press brake/hand brake method described here;

Begin with the parking brake off and the engine off.

Start engine.

Apply parking brake and press the foot brake twice then let the parking brake off again.

Press the foot brake and pull the parking brake on and off twice then let the foot brake off again.

Finally pull the parking brake on and press the brake twice.

The VSC light will now come on and stay on until you switch the ignition off again after which the VSC defaults to on again.

2. Use a piece of wire to short out the pins 4 and 12 of the DLC plug shown here;

Here is a photo of the plug just by the bonnet pull;

3. Raising the vehicle off the ground

Then there is this method but it is labour intensive and the MOT tester isn't likely to thank you for it! It requires the other wheels to be allowed to turn while the individual brakes are tested (albeit fail safe as no damage can be done). It means the car has to be lifted to get the remaining wheels off the ground and the handbrake off so that all wheels can turn freely when the transmission locks up - like this;

Remember that this also has to be done when testing the rear wheels and the tester is going to love that too! The easiest way is in disabling the VSC as described in either 1. or 2. above. The first is easy enough with a bit of practice and the second needs a bit of confidence but is also easy. I printed the first procedure and left it in the glove box. Just remember that when taking the car for test to have it disabled and don't worry - the first time the ignition is switched off the VSC will reset itself so do that before leaving.

[nest]

A little hint: for the fist method, don't push the brake pedal to firmly or it will activate the Hill Assist Control.

[anchorman]

A little hint: for the fist method, don't push the brake pedal to firmly or it will activate the Hill Assist Control.

This is a good point Nest and just to clarify - pressing the brake only needs to be hard enough to work the brake lights and working the hand brake only needs to operate the little warning light on the instrument panel. These are the electrical signals that in combination lock out the VSC/TRC.

[kencat]

A little hint: for the fist method, don't push the brake pedal to firmly or it will activate the Hill Assist Control.

This is a good point Nest and just to clarify - pressing the brake only needs to be hard enough to work the brake lights and working the hand brake only needs to operate the little warning light on the instrument panel. These are the electrical signals that in combination lock out the VSC/TRC.

will this enclude the xt 3 ?

[anchorman]

A little hint: for the fist method, don't push the brake pedal to firmly or it will activate the Hill Assist Control.

This is a good point Nest and just to clarify - pressing the brake only needs to be hard enough to work the brake lights and working the hand brake only needs to operate the little warning light on the instrument panel. These are the electrical signals that in combination lock out the VSC/TRC.

will this enclude the xt 3 ?

Yes. Although the XT3 doesn't have VSC it does still have an electronic 4WD system that will sense a wheel turning and as such will operate the traction control and the rear axle clutch.

[didje]

A little hint: for the fist method, don't push the brake pedal to firmly or it will activate the Hill Assist Control.

This is a good point Nest and just to clarify - pressing the brake only needs to be hard enough to work the brake lights and working the hand brake only needs to operate the little warning light on the instrument panel. These are the electrical signals that in combination lock out the VSC/TRC.

will this enclude the xt 3 ?

Yes. Although the XT3 doesn't have VSC it does still have an electronic 4WD system that will sense a wheel turning and as such will operate the traction control and the rear axle clutch.

[didje]

A little hint: for the fist method, don't push the brake pedal to firmly or it will activate the Hill Assist Control.

This is a good point Nest and just to clarify - pressing the brake only needs to be hard enough to work the brake lights and working the hand brake only needs to operate the little warning light on the instrument panel. These are the electrical signals that in combination lock out the VSC/TRC.

will this enclude the xt 3 ?

Yes. Although the XT3 doesn't have VSC it does still have an electronic 4WD system that will sense a wheel turning and as such will operate the traction control and the rear axle clutch.

Hello is this just scaremongering

Toyota/Rav is not the only vehicle with this type off brake/fwd system the principle is very common,anyone who thinks your MOT station is going to start shorting wiring connectors and tying your car down is mistaken can you imagine the possible consequences.Every testing station should have a Bowmont or similar brake testing system(google it) and will be familiar with its use on 4wd systems of all kinds

Didje

[PhilGee]

I take them down a quiet road and perform a brake test with a decelerometer.

[anchorman]

A little hint: for the fist method, don't push the brake pedal to firmly or it will activate the Hill Assist Control.

This is a good point Nest and just to clarify - pressing the brake only needs to be hard enough to work the brake lights and working the hand brake only needs to operate the little warning light on the instrument panel. These are the electrical signals that in combination lock out the VSC/TRC.

will this enclude the xt 3 ?

Yes. Although the XT3 doesn't have VSC it does still have an electronic 4WD system that will sense a wheel turning and as such will operate the traction control and the rear axle clutch.

Hello is this just scaremongering

Toyota/Rav is not the only vehicle with this type off brake/fwd system the principle is very common,anyone who thinks your MOT station is going to start shorting wiring connectors and tying your car down is mistaken can you imagine the possible consequences.Every testing station should have a Bowmont or similar brake testing system(google it) and will be familiar with its use on 4wd systems of all kinds

Didje

I'm not aware of any other vehicle that has this sort of 4WD system but I am always willing to learn. I have a friend who has a Merc E Class and his hand book makes a point of forbidding the use of a normal brake roller test. That vehicle is RWD but has VSC!

As for the use of a Bowmonk (I have one in my garage and the other popular one is the Tapley Meter). They will measure overall braking deceleration but they cannot determin which brakes are doing what. They certainly wouldn't show if one brake was low in effort and they would not show an imbalance. They are also not very accurate and depend very much on where they are positioned and how well they are set up. In my previous job as a brake system testing and development engineer they certainly wouldn't have been accepted by any current vehicle manufacturer.

Is it scare mongering? I can only tell you that the RAV 4.3 manual makes a big issue about it. It may be that only the right conditions would cause damage but I imagine they have gone to such trouble because there is a risk. I'm not advocating that all owners should attempt to disable the VSC for MOT by shorting wires - there are several options anyway (although there are many competant owners that are capable of doing it) but if you print the post out and take it to the test station they should be able to do it quite easily.

The bottom line is I have attempted to make people aware that the makers of the vehicle consider it important. If anyone wants to try brake testing without taking the recommended precaution it is up to them.

[didje]

I take them down a quiet road and perform a brake test with a decelerometer.

Thats what i meant to say but had trouble spelling it desell / diesel /deceloo/ oh you know what i mean

[snowjoke]

Presumably not a problem for 4.2s with VSC (XT4s, XT5s and XTRs), since no-one's mentioned it?

[junebug1701]

1. Use the press brake/hand brake method described here;

Begin with the parking brake off and the engine off.

Start engine.

Apply parking brake and press the foot brake twice then let the parking brake off again.

Press the foot brake and pull the parking brake on and off twice then let the foot brake off again.

Finally pull the parking brake on and press the brake twice.

The VSC light will now come on and stay on until you switch the ignition off again after which the VSC defaults to on again.

2. Use a piece of wire to short out the pins 4 and 12 of the DLC plug shown here;

I tried this and all it does is make my P/S light flash rapidly. The handbrake method works fine.

[anchorman]

Snowjoke

Yours is a different setup altogether although brake test time should be kept to a minimum. For 4.1s the diff lock button should be set to off. For 4.2s go ahead with the test as briefly as possible. Refer to the following info on page 9. You will also see on page 10 that there are special requirements for high speed dyno testing but perhaps the most important is that later info on towing. I have seen many gearboxes completely destroyed by incorrect towing methods. This is because the gearbox relies on the engine running and the wheels turning to keep the internal oil pump working and the shafts lubricated.

James

Maybe the ECU is different for yours but as long as the handbrake method works that is OK. I don't know what the test requirements are for the US. I thought there was only a moral obligation to keep the brakes serviceable to avoid litigation issues?

roller_test.pdf

[HEMI]

when it comes to MOT time,VOSA's info knows that the car cannot be roller brake tested(RBT) and will put a note on the testers test sheet that this car must be Tapeley Tested(that thing they put on the floor of the car and drive then brake and look at the reading)any full time 4WD has to be Tapeley tested unless you can safely turn off the 4WD,even if the car has a LTD slip diff you cant RBT it,it has to be tapeley tested(deceleration test,as its properly named)

[luke4x4tech]

Don't go sticking wires into the dlc3 socket!!!

just take it to any MOT station and let them get on with it.

as an N.T myself we are all aware of 4x4's and the brake roller tester it also gets flagged up on the VSI ,

so if a tester puts it in the rollers and breaks it he/she should learn to read or go on a refresher day.

[anchorman]

There are different points of view on this one so maybe I should just reiterate one or two points;

Although using a decelerometer for a brake test is at the discretion of the tester for "special applications" it is not a good method of measuring brake performance as it only indicates overall deceleration and would not show any imbalance or single brake deficiency. For this reason the use of this method should be discouraged.

I accept that sticking wires into the DLC tester is also not good practice for anyone other than somebody who is confident or competent and if not the owner can print the info in post 1 and take it with them to the tests station. In most cases the tester will know what to do but I'm not sure I like the idea of having to sort out who is going to pay for a broken RAV after they have learned how not to test it.

It will certainly say to the tester that the owner is aware that special requirements apply and is going to know just what has happened if they take any unnecessary short cuts.

This post is pinned as "beware" info, not an instruction.

[Nightstalker]

Hi all...

Big Red just flew through her first MOT... Wouldn't have expected anything else to be hoest...

One thing though...

I did mention the VSC issue mentioned above and they (Octagon in Reading) were not aware of needing to set the system to break test.

I was adivsed that their break test system is programmed by them entering the reg number of the car and all else in magic that happens in the 1s and 0s domain...

Anywho, nowt reported as faulty and as all breaking seems ok I guess nowt has happened to the VSC system either....

regards

Rob

B)

[Fujisan]

Big Red just flew through her first MOT...

regards

Rob

B)

Nice one Rob

[anchorman]

I have moved this back into the RAV section but put a link from the maintenance section to tidy the top of the RAV page.

[HEMI]

There are different points of view on this one so maybe I should just reiterate one or two points;

Although using a decelerometer for a brake test is at the discretion of the tester

its not at "our" discretion,its stated on the "test paper",when I get back to work on tues I'll quote it from the vosa paperwork that we get for 4wd vehicles,basically it states blah,blah,blah,this vehicle must not be RBT,unless it can be safely turned off,so we just taperley them

[ormi]

has or is any one a tec for toyota or a mot tester for toyota wrote on this topic???????

i have mot'd 00's of ravs new and old and never have i ever had any problems ever(the rbt doesn't turn fast enough)and as you can see from my sig i'm not a stranger to toyota.

most of this sounds like scare tactics.

the only cars i have really seen go wrong is anything permanant four wheel drive.

[anchorman]

OK I understand but I also reiterate that a tapley meter test is wholly inadequate as it only measures total decel and not the individual wheel brake force. You could easily have one wheel well down on output and the tapley meter wouldn't find it.

You can safely turn it off and do a definitive brake test by following the above instructions - that is the whole point of this post.

[ormi]

i'll get the boss in on this one hes a member too and worked with toyota for over 20 years he also is a mot tester and also has been on the same rav 4 courses as me.

our brake tester mesures all 4 wheels individual ie as long as say the left front is turning on its own in the rbt and the reading is 0 before pressing the brake you are testing that individual wheels force but if the wheel has a reading then you either have a sticky caliper or the machine is getting a reading from the diff(ie diff wind up)the rav doesn't suffer from diff wind up nor do you get a reading when testing individual wheels(unless pressing the brakes)their isn't even any tec bulitins on this from toyota.

i supose its a good what iff topic though.

[anchorman]

Blimey, I didn't realise that moving this old chestnut would generate such a reaction but hey ho - into the breach!

In the first place I know what the brake roller test is all about and how to detect a rubbing brake so I'm not quite sure what you mean by that. Secondly I can assure you that although there may not be a TSB on this subject there is definitely quite a long section on it in the Genuine Toyota workshop manual of which there are several references right at the top of this thread. I can only assume that you haven't read this information during all your years of working for them.

Now let me put this into perspective. I am not suggesting for one minute that if you fail to heed this warning which your employer has issued that you will definitly wreck a transmission but the fact that they have issued it suggests that if the conditions are right you most certainly run the risk of causing extensive damage otherwise I can't imagine why they would publish it. If you would like me to post the article that gives this warning just say and I will do so or you can look in your own system.

Next, in my set of vehicle engineers top trumps cards, 17 years in brake testing and development for most of the worlds vehicle manufacturers beats yours and your bosses time of working on brakes for some of the time and if your gonna get your boss I'm gonna get my mate and he's bigger than your boss.

Only joking ormi but I intentionally avoid getting too heavy on this subject and with respect you might be better letting this go ;)

[ormi]

i was only going to ask him due to the fact he has and loves working on 4x4 and has done for many many years and we have had no issues with damaged diffs etc so i was going to ask if he ever has had any diffs/gearboxes give up the ghost. but as said i know audi 4x4 systems hate the rbt as do the golf 4x4 and almost everything permanant 4x4.i was mainly pointing out that things weren't as bad as what was being posted.