How does the tyre pressure monitor system work? I can't figure it out. What does the little switch in front if the gear stick do? Owners manual wasn't very helpful, assuming I was looking at the right pages.....

It uses the abs system to work out differences in the rotational speed of the wheels.

The button resets the system, ie after you have inflated the tyres

A wheel with a flat tyre is smaller than an inflated one, therefore will turn more revolutions for a given distance. The ABS sensors monitor this. The button tells the ECU to do a basic calibration so it has a baseline figure to reference the wheel speeds to.

It's not really that accurate and is not a replacement for internal pressure sensors in that it doesn't actually measure the pressure. It should really be called a wheel size monitoring system.

Can it be disabled?

Can it be disabled?

Why would you want to do that?

Can it be disabled?

 

It could be disabled using VCDS. You would basically just untick the box to tell the car that it doesn't have TPMS.

 

Phil

It probably can by changing the coding in vcds to mark it inactive. However as gadgetman says why? It is good at what it does which is wheel size monitoring as metblackrat says but it is not a substitute for tyre pressure checking. Know its limitations and its good for detecting large-ish drops in pressure.

Adam

Mine activated, when there was a nail in the rear tyre,

So it was very useful, it just prompts you to have a look & check pressures

Why would you want to do that?

Just a question...

It used to be on/off all the while when we first got the car. It's behaving at the minute though, so I'll see how it goes

Everyone, thank you for your replies.

It does work (as outlined above) and IF you remember to reset it after checking your tyre pressures it picks up punctures pretty well. Mine has found a couple of nails.

 

It dosn't warn you if the pressures are dropping in all tyres. It works by measuring the differnces between the wheels. If they're all dropping naturally it won't warn you to fill up.

On my car it seems a pretty useless system.  I hit debris in the road and a tyre completely deflated - no warning from the tyre pressure monitoring system.  Fitted the spare wheel (with correct pressure) and after ½-mile the tyre pressure monitoring system displayed an error.

Its worked on one of mine before, its better than having no detection at all.

The system in the Mk3 is the same but it does now tell you which tyre is affected which is a nice improvement, save you having to check all four. Only thing I dislike about the Mk2 system is not knowing which tyre is affected without looking.

Edited 26 December, 201312 yr by pipsyp

The main comment that gets me is when people say it didn't warn before a blowout.

I don't think any tyre pressure system can do/know that.

On my car it seems a pretty useless system. I hit debris in the road and a tyre completely deflated - no warning from the tyre pressure monitoring system. Fitted the spare wheel (with correct pressure) and after ½-mile the tyre pressure monitoring system displayed an error.

If the tyre completely deflated straight away and you stopped quickly then the system wouldn't have had time to work. That's not how it is intended to work. If you have a space saver spare which has a different total diameter to your normal wheels then the system would pick this up and why it needs to be reset after a wheel change.

The system is designed to spot slow punctures not catastrophic failures. You need to move a sufficient distance for the system to spot a trend in the relative wheel speeds, otherwise it would operate too often as a result of road conditions, turning etc.

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Mines just activated, checked all tyres which were fine pressure wise....turned out my offside rear brake caliper has decided to seize hence creating a rolling resistance

Grrr this 10 plate is causing me more problems than my 03 one

 

Phil

If the tyre completely deflated straight away and you stopped quickly then the system wouldn't have had time to work. That's not how it is intended to work. If you have a space saver spare which has a different total diameter to your normal wheels then the system would pick this up and why it needs to be reset after a wheel change.

The system is designed to spot slow punctures not catastrophic failures. You need to move a sufficient distance for the system to spot a trend in the relative wheel speeds, otherwise it would operate too often as a result of road conditions, turning etc.

Sent from my Nexus 4 using Tapatalk

Thanks - that makes sense.  However. I did have to drive approx. 1/4 mile to get out of a narrow and steep single track lane (not the place to stop to change a wheel).

 

My 205/55-16 spare tyre has a rolling diameter less than 1% different to the original 225/40-18 and was driven on for about 1/2 mile before the warning on 'low pressure' was displayed.  Impressed the system is that sensitive.