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Child Item

Polo Tire Pressure Monitoring

John.G

Decided to test the TPM on my 3 year old Polo, pumped tires to 2.0 bar, then reset the TPM, reduced RR Tire by 0.5 bar to 1.5bar and went for ~ 2 mile spin, no alarm, returned, repumped tire to 2.0 bar, went for another spin (did not reset TPM) no alarm (and not expected this time). Reset TPM again.

Why no alarm?.

When I purchased the car the tire pressures were 2.3 bar and I didn't pump them until they fell (all uniformly) to 1.9 bar, again I didn't get any alarm in falling from 2.3bar to 1.9bar, but can't confirm if the TPM was enabled/set up when the car was delivered so maybe benefit of the doubt there.

AFAIK the TPM uses the ABS to monitor the wheel(s) speed so any change in pressure flags a alarm, it stores each wheels "details" once reset, Don't know what the trigger difference is but 0.5bar should certainly do the trick?. Again presumably the car does not have to be on the move when the tire pressure changes which would be pretty daft.

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[Deleted User]

https://www.boards.ie/discussion/2058238793/polo-tire-pressure-monitoring

John.G

Did it exactly as the 7 very simple steps shown in 5.1.1.

Atlantic Dawn

When it has gone off in my car it's roughly a 25% drop from the reset figure where it was triggered, both times after a puncture.

John.G

OK, seems a lot of deviation required to trigger it, I dropped mine from 2.0 to 1.5, exactly 25% so will try it later on today at 1bar, a 50% deviation and see what happens.

John.G

https://www.boards.ie/discussion/comment/118837318#Comment_118837318

Reset TPM at 2 bar each, reduced one to 1 bar, drove 2 miles, no alarm. I presume its not something daft like the car having to be moving when tyre pressure changes?

[Deleted User]

What readings the computer can see? Possible faulty sensor... or garbage air like every pump station have (no water and oil separation)

Toyotafanboi

I've seen you slag pretty much everything at this stage, but knocking the quality of air provided at filling stations, you're some operator.

How could "bad quality" air even effect a TPMS system ran off the ABS sensors.

Are you letting down a front or rear tyre?

kirving

The TPMS may be calculating the pressure in each wheel based on rotation speed, and in order to do this they've devised a calibration table where X pressure = Y wheel speed.

This won't necessarily be linear and will be affected by the tyre temperature, ambient temperature, tracking, and probably does a partial reset each time you start the car.

Unless the wheel is very very low, the car will most like want you travelling in a straight line, above a certain speed, for a minimum number of rotations, and other tyre pressures stable. You probably have to run it for longer to get a result.

Does the car tell you each pressure in PSI or Bar, or just which wheel is low?

John.G

https://www.boards.ie/discussion/comment/118838379#Comment_118838379

I use my own (electric) pump checked with a pencil type gauge.

https://www.boards.ie/discussion/comment/118838770#Comment_118838770

I am letting down the rear right tyre.

https://www.boards.ie/discussion/comment/118838836#Comment_118838836

I think I am probably expecting too much from the system too fast maybe?, as in the tyre deflating in the drive and then expecting the TPS warning up as soon as I drive off.

I just think its a general alarm and doesn't say which wheel.

EDIT

The manual states: "After a extended driving time with driving different speeds , the system will automatically learn the new values and monitor them"

Strange how it didn't do this over a 2 year period in falling from 2.3 to 1.9bar but maybe it was because they all fell to exactly the same reading, to the nearest psi in fact.

I have reset the TPS at 2 bar, will run it for a week to give it plenty of time to do some learning, then reduce one tyre by 0.5 bar and see what happens.

kirving

Some systems are more complex, using sensors in each wheel, and are as much about reminding you to have the correct pressure for fuel economy purposes as warning you about a flat.

TPMS in mandated by law in the US, but as far as I know a basic enough software based system is acceptable, so most manufacturers then copy the same software to other vehicles worldwide.

A software based system would struggle to detect all wheels dropping simulatiously. Sure, wheel speed vs engine speed ratio would not be the same as it was months before, but this ratio also varies as you drive and tyres heat up, and also due to ambient temperature and humidity.

They can't (for example) reliably go so far as to use the external temperature sensor as yet another correction factor for the engine/wheel speed ratio to detect minor fluctuations in pressure. But a gross change will be detected and allow you to slow down before a blowout.

I got a blowout in the right rear of a RWD E-Class and barely even felt it to be honest. I understand why many people keep driving until it disintegrated. Took a few hundred metres before the (software / ABS) warned me, if I remember correctly, and the steering just felt a bit loose at 120km/h.

[Deleted User]

https://www.boards.ie/discussion/comment/118839421#Comment_118839421

True, they make everything cheap as possible. It gives to people the false feedback like everything is ok.

Toyotafanboi

I dont think he meant that.

You dont want anything too super super sensitive in a TPMS warning system anyway. The end user really only needs to know is it dangerously low or not, a bit like oil or coolant level warnings.

Dont need the TPMS warning coming on when the tyre loses 1 psi.

Irish Steve

https://www.boards.ie/discussion/comment/118839520#Comment_118839520

Please, give us a rest, you've done nothing other than spout irrelevant drivel all over this thread, and contributed nothing positive to actually help the original poster to determine if their system is working correctly or not.

Some of your more outrageous comments force me to wonder if you actually have any real motor trade experience, or if you spend your time using Google search in order to try and justify your often questionable opinions about so many subjects. Yes, there are bad apples in any barrel, but the motor trade is not full of people trying their hardest to defraud people on a daily basis, and your posts are all too often a very hostile and discouraging opinion of a trade that is under huge pressures from all sides as a result of the many events that have happened over the last few years. If you can't say something positive in a thread, please, don't say anything, it will make the site a much pleasanter read for all involved.

[Deleted User]

https://www.boards.ie/discussion/comment/118841223#Comment_118841223

What a heck...

John.G

Looks like the car must be in motion while the pressure changes to flag a alarm.

I reset the system with all tires at exactly 30 psi, did over 120 kms, reduced pressure in one tire by 14 psi, to 16 psi, drove another 10 kms or so, no alarm.

John.G

Hallelujah!!, Tyre ptrssure monitor flagged a alarm this morning " Right Front Tyre Low Pressure" checked all tyres which all had been pumped to 32psi (2.21bar),

Right Front: 18psi

Right Rear: 29psi

Left Front: 26psi

Left Rear: 30ps

Tyre alarm up when R.Front was 10.33psi (0.713bar) lower than the averaged other 3, or 18psi lower than the 32psi reset, 36.5% of the averaged other 3 (now) or by 43.8% of the original reset at 32psi.

zg3409

Without a sensor on each tyre actually monitoring the pressure all the car can do is monitor the relative rotation of each hub in all 4 corners to see if there is an imbalance in rotation. It can probably only do this while driving straight as when cornering each wheel will rotate less or more on bend.

If all 4 tyres slowly drop pressure then the relative difference in speed will be the same. It's meant to be a low cost rough alert to a sudden large pressure change while driving, and may give false alerts if wheels swapped or wrong size tyres. Many cars don't even show the driver which wheel is suspect, so all 4 wheels may need to be checked which is hard to do visually. After pumping up all tyres to correct value you need to reset system so it knows what normal looks like.

For cars with a pressure sensor on each tyre tube, they only wake up when car is moving to save battery life, and they only send a radio message to the car at start up and then if a sudden pressure fault is noticed. If you move wheels around it may report wrong place on car, but some systems can auto relearn the location of the tyres based on radio signal strength. I think the newer laws require a sensor on each tyre as the older systems were not great at speed of alert and giving details of location and actual pressure.

John.G

Friends Kia Sportage displays all 4 tyre actual pressures.