TPMS Failure?

[BigRedSwitch]

When I bought my Auris some 6 months ago I checked the tyre pressures and they were all 36psi.  I reset them to 33psi as the manual specifies and reset the TPMS system.  Since then the TPMS warning light has never come on and I assumed all was well.  I checked the pressures a couple of days ago and they were all below 30psi.  So why didn't the TPMS light come on?  Could it be that TPMS only reports loss of pressure when the car is running and that any loss of pressure overnight say, does not?  Anyone any ideas? 

It's due a service next month so I'll ask them to check it if it appears that the system may be faulty..

[FROSTYBALLS]

Think if the system detects that a tyre is a certain percentage below the set pressure, the system will show a solid warning light - commonly I think the percentage is approx 20%. If there is a fault with the system, the light should flash.

Some systems use pressure sensors in each wheel (direct system), some use the ABS sensors to measure rotational differences between the tyres (indirect system).

Could be that the loss of pressure in your tyres hasn't hit the required threshold to trigger the system. TPMS isn't a replacement for regular checking of the pressures and condition of tyres though.

[BigRedSwitch]

Thanks for your reply Mike.  I will revert to my old practice of checking tyre pressures monthly.  I'll tell my dealer and if he reveals any nuggets of information I will report back.

[furtula]

You can easily deflate one tire and confirm that the system either works as suggested above, or it's in fact broken.

[j66]

Set at 36 interesting, I’ve recently set mine to 36 getting better mpg (fully loaded)

Dose it say 36 = eco on your tyre pressure chart @ the drivers door B pillar.


Sent from my iPhone using Tapatalk

[BigRedSwitch]

On 8/24/2018 at 9:47 AM, j66 said:

Set at 36 interesting, I’ve recently set mine to 36 getting better mpg (fully loaded)

Dose it say 36 = eco on your tyre pressure chart @ the drivers door B pillar.

No "eco" setting at all.  The only other pressure it mentions is 38psi for speeds > 100mph.

[BigRedSwitch]

On 8/22/2018 at 11:02 AM, FROSTYBALLS said:

Think if the system detects that a tyre is a certain percentage below the set pressure, the system will show a solid warning light - commonly I think the percentage is approx 20%. If there is a fault with the system, the light should flash.

Asked in my Toyota dealers yesterday and they said that if the pressure was set at 33psi then they wouldn't expect TPMS to alert me until pressures were down to around the 26psi mark.

Frosty was bang on the mark again!

[furtula]

So basically this system is useless when you compare the hassles of it. If the pressure is down that much, you would definitely feel and could see it. The car i presume would also probably pull a bit to the side.

 

[FROSTYBALLS]

TPMS isn't intended to help you keep a regular check of tyre pressures, it is supposed to warn of a large loss of pressure compared to the pressure it is set at. As regards hassle, one just needs to press the reset button after one has checked and changed the tyre pressures. 

We've got TPMS on both cars - on the i20 the system has shown no warnings, and once last year on the Aygo the system warned of a loss of pressure (which turned out to be a nail in one front tyre).  Both cars are checked regularly as regards tyre pressures and condition.