Evening getns. I have a 2010 Octavia VRS with standard alloys and tyres - 225/40/18.

Recently the tyre pressure light has came on so I popped the car round to the garage to check the pressures. All of them were different. I couldn't see in the car what they should be so I put them all to 32psi. However the light has stayed on? A few days later none of them appear to be losing any pressure but the light remains on. Any ideas??

Also does anyone know what the correct pressures should be?

**gents!!

Have you reset it as per the manual (think you have to.hold the button in until it bleeps? The tyres pressures are quoted on the inside of the fuel flap IIRC?

If it's not the above it could be an ABS sensor on one of the wheels playing up.

As above

hold down the tpm button till it boings - u should do this everytime u top up ur tyre with air.

Yep, the wheels dont have air pressure sensors in them, the ABS module monitors the rolling circumference of all four wheels and throws a warning if there is any large scale change.

the rather unfortunate thing is the system doesnt tell you which wheel; given each wheel has a sensor it should be able to technically but doesnt.

The set button basically tells the ABS unit to re-learn the rolling circumferences of all four wheels, does it over a period of a few miles after first pressed. Once the alert is triggered it wont go out until a reset has been completed.

best to turn ignition on whilst engine isnt running (might work whilst running but cant say ive tried it) and press set button for a few seconds, as said above you'll get a bong and the light on the dash will go out.

As others have said if it keeps going off and the pressures are ok points to an ABS sensor issue.

...the ABS module monitors the rolling circumference of all four wheel...

I realise this is a geeky question, but how does it do that? Is the rpm of each wheel measured individually and related to indicated vehicle speed?

Also this will happen when you change tyres

I realise this is a geeky question, but how does it do that? Is the rpm of each wheel measured individually and related to indicated vehicle speed?

I read about this when I fitted mine. An underinflated wheel relative to the others will travel less distance (its circumference) every time it rotates. This difference in distance can be detected and reported back. Of course if all four wheels deflate at the same rate (which is quite likely over time) no difference will be evident and so this so called indirect tpms is not a substitute for regular checks.

Adam

This has worked for me well in the past too. Was on the way to work in my old Fabia vRS when the warning threw.....i drove to work and when i parked up i could hear the hissing.....id driven over a nail just before the warning came up. I kept going because i thought it was just throwing a wobbler as it did on my Mk6 Golf.

it was by pure chance that me keeping on with the remaining 2-3 miles of the journey kept enough air in the tyre to get me there. Id say id it ever does go off stop and check as it is pretty reliable.

This has worked for me well in the past too. Was on the way to work in my old Fabia vRS when the warning threw.....i drove to work and when i parked up i could hear the hissing.....id driven over a nail just before the warning came up. I kept going because i thought it was just throwing a wobbler as it did on my Mk6 Golf.

it was by pure chance that me keeping on with the remaining 2-3 miles of the journey kept enough air in the tyre to get me there. Id say id it ever does go off stop and check as it is pretty reliable.

+1 Agreed.

 

My light came on a few weeks back. I thought it was strange as just before that I had been to the garage and topped up the tyres and reset the system. When the light came on I pulled up to find one of the valve caps missing, even though I know I had refitted them. On checking it was down to 20psi. I can only put it down to those pesky kids !!!!. Topped up and reset the system once more and it has been fine for the last four weeks or so and the pressures were all ok when I went to the garage last.

Edited 2 November, 201312 yr by radders567

I agree. Its a useful tool as long as you know its limitations and don't over rely on it.

Mine detected a 5psi drop recently a day after I had a tyre changed. I had checked the pressures immediately after the tyre was fitted so was content that all was ok with my tyres.

It turned out to be a dodgy valve which I might not have noticed for another couple of weeks otherwise.

 An underinflated wheel relative to the others will travel less distance (its circumference) every time it rotates. This difference in distance can be detected and reported back.

I'm guessing that what is actually measured though is wheel rpm, right?

Edited 2 November, 201312 yr by Ultrasonic

Yes I would guess that is probably how the measurement is taken, some kind of magnetic contact made on every rotation perhaps.

What pressures are you setting yours at for you vrs had My car for two weeks Checked pressure today and Mine are set at 30psi Is this correct?

It depends on the wheel size I think. Mine are on the inside of the filler flap.

I realise this is a geeky question, but how does it do that? Is the rpm of each wheel measured individually and related to indicated vehicle speed?

 

The ratio of the rotation speed at the gearbox output to the rotation of each wheel. If the ratio changes, then the rolling radius of that wheel (or those wheels) has changed and it alerts you. Thats how it can tell you if even all four wheels have gone flat at once.

 

So in essence, yes, what you said

That suggests it is not relative differences between the wheels then, which is what I read.

I would have guessed it just counts the revolutions for each wheel over a set distance and compares that to the last count over that distance for each of the four wheels. Over a reasonable distance the effects of steering etc average out so any difference would mean that the tyre pressure had changed.

It is a very useful tool as long as the tyre pressures are also checked regularly. If they are not then there is every chance one tyre's pressure will drift slightly out of tolerance and the alarm will go off. Cue stopping in the rain on a dark night at the side of a busy road to check the tyre pressures, quickly followed by scratching of (cold wet) head to figure out why perfectly acceptable tyre pressure variation was setting off the alarm. Not that I would have had to learn this by experience of course . . . .

The only time that mine has come on was about 10 miles after swapping the front wheels on to the back and the backs on to the front because I hadn't held the button down and reset the system. I'm guessing that the system works by using a phonic wheel or something similar.

What pressures are you setting yours at for you vrs had My car for two weeks Checked pressure today and Mine are set at 30psi Is this correct?

 

Mine are set at 34 Psi all round ( 225/40/18 Toyo Proxy 4 ) Tyre wear is even

Thanks for all the replies.

I never knew about the reset button!.... However, I've pressed it and nothing happens so looks like it could be a sensor? It's in for a service with skoda next month so will get it checked then.

Thanks for all the replies.

I never knew about the reset button!.... However, I've pressed it and nothing happens so looks like it could be a sensor? It's in for a service with skoda next month so will get it checked then.

Press and Hold, about 3 to 5 seconds till it bleeps

you've got to press and hold it until it makes a noise. Have you done that?

 

It basically sets a default value for the car to monitor

I've tried a good few times and held it for up to a minute!