Dwrav4.3

Disable VSC/TRC for brake test at MOT

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So I've just read this and it seems to me that based on method 2, shorting the pins, we can easily fit a switch into the wiring loom so that when it's pressed the pins are shorted and the vsc is turned off, when is not pressed the vsc is untouched and works as normal... Whats wrong with that plan? Have I missed something? 

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Does anyone know if I'm right or wrong? 

Seems simple so maybe someone would have done it before? 

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Perhaps we haven't read what you have (you didn't give a link), so we don't know what you are asking about?

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It's in the title, on the rav4 guides page on this forum there are two posts about vsc and turning it off for Mot testing. Just thought it'd be a well known thing but no one knows what I'm on about! 

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OK. here's a link so others don't have to search around.

My view is that rather than just a "press switch" which the tester would have to remember to keep pressed whilst he was testing, wire the shorting circuit through a hold-on (aka latching) relay which would open when the ignition was switched off.  That way it stays on whilst the engine is running.  The relay would need to be a double pole single throw.

Quick and dirty sketch:

Brake-test.jpg

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Tens of thousands of permanent 4 x 4 vehicles are MOT tested every year. The system flags up to the tester what precautions need to be taken on a particular vehicle. Many stations have 4 wheel testing systems. In some cases the station will refer you elsewhere. The regulations also allow a Tapeley meter to be used - this involves a short drive in the vehicle.

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I saw the thread on the guides page and thought it was some sort of problem, I've only just got the rav so I don't know the details but I just thought to solve it an easy way would be an on/off switch, on it's shorted off it's not.

Not really sure why there is a guide to something that doesn't really matter then!

Thanks for the replies though. 

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A switch could be forgotten in the wrong position 😧

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That's true it could be left shorted if not careful, I'm not sure how the system works, if you short it briefly is the vsc off until ignition reset or is vsc only disabled while the short is in place?

Would there even be anything on the display to tell you it's disabled? 

I also read something from Toyota saying that if you get stuck off road, turn off vsc and you'll get more power to rock yourself out of the predicament! 

But they didn't (in this model at least) fit a way of turning it off.

It's all a bit strange and possibly unnecessary.

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The way I read it, the light stays on and the VSC is disabled until the ignition is turned off.  It isn't entirely clear whether the short can be removed whilst the engine is running.  The words are hard to read and don't really make sense.  It suggests that, although the ignition is off when the short is applied, there is a reaction (can't read the last word) from the light.  Surely that would only occur when the ignition is turned on.

Actually, the hokey-cokey with the handbrake and footbrake is pretty easy to memorise, so I would just go with that.

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On second thoughts, my guess is it works like this:

Apply the short with the ignition off.  Nothing happens. Keep the short in place and turn the ignition on.  The lamp lights and VSC is off.  Remove the short and the lamp stays lit with the VSC still disabled.

Turn ignition off, the lamp goes out, and VSC will work next time ignition is turned on.  You could try that and see what the lamp does.

If I'm right, you would not need the relay circuit above, just a momentary press push to apply as the ignition is turned on.

EDIT:  On third thoughts, it doesn't say apply a short.  It says "connect the SST", whatever that is..  There's an assumption that that applies a short but I don't like assumptions with electronics, so I would not try it without being sure what an SST is.  

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I really don't know why owners are concerned - the peculiarities of different vehicles is built into the MOT software which dictates what needs to be done - it isn't the case that a plethora of vehicles with ABS, TC, SC etc are being damaged during testing.  

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It looks more and more like trying to solve a problem that doesn't exist! 

Sorry I brought it up! 

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47 minutes ago, Dwrav4.3 said:

It looks more and more like trying to solve a problem that doesn't exist! 

Sorry I brought it up! 

No problem ... in his opening sentience Don (Anchorman) says "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" - i.e. the concern was raised some time in 2008 / 2009 when the first of the 4.3s, with their then 'new' AWD system, became due for their first MoT. A decade on we know from experience that it really isn't a concern - and probably wasn't then either - and MoT testers really do know what they are doing ... 🙂

The 'tutorial' is still useful as it explains how to disable the VSC (should you ever want / need to do so).

Enjoy your RAV!

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On 7/23/2019 at 7:01 PM, philip42h said:

MoT testers really do know what they are doing ... 🙂

Knowing a few testers personally, I would disagree 😂

Ironically my Dad took the 4.3 that’s been relegated to dog walking duties/tip runs for it’s MOT Monday last, clean pass, no advisory. This Monday, after doing all of 20 miles since the test, the rear tyre blew... it was down to the canvas/belts in two places on the inner edge, the other side was almost as bad.

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Simply not acceptable and the DVSA should be informed via their complaints procedure. It might seem that complaining that a vehicle passes unjustifiably is not in your best interests. The reality is that it's your safety at stake and an unjustified pass is certainly not in anyones best interests. 

As in all walks of life there are those who are diligent and honest and there are those who are not. We all have a duty to report testers who we know could be putting lives at risk. The DVSA have systems and procedures for monitoring the quality of testing and have upped their game in recent years. The number of examiners and testers being banned or warned increased dramatically last year. 

Your experience also supports regular checks by owners on tyre pressures, tyre condition, brake fluid level etc etc. Clearly tyre deficiencies need to be spotted well before parts of a tyre are down to the canvas!

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