Tpms problem

[Johnlex]

So I have tpms sensors on my Lexus IS 250c.

i put my spare wheel on which is a standard valve. 
There’s no light on dash or warning to say there’s a problem with the tpms. 
there should be a icon constantly flashing ??

 

does anyone know what the issues could be please 

[NemesisUK]

Is the TPMS equipped wheel in the boot?

[Johnlex]

2 minutes ago, NemesisUK said:

Is the TPMS equipped wheel in the boot?

No it’s a another 5 spoke Lexus alloy with tyre I bought as I have a 250c I have gel pump in boot

[Johnlex]

What’s strange @NemesisUKis that the dash light should of come on but hasn’t 

[Texas]

Does this system work with a wireless remote sensor in each of the car wheels tyre valve or via the abs ring detecting a out of sync wheel motion due to a different wheel diameter and calculating a pressure drop?

[LenT]

19 minutes ago, Texas said:

Does this system work with a wireless remote sensor in each of the car wheels tyre valve or via the abs ring detecting a out of sync wheel motion due to a different wheel diameter and calculating a pressure drop?

I think this Lexus article on the TPMS may answer these questions.

https://mag.lexus.co.uk/tyre-pressure-monitoring-system-what-is-tpms-and-how-does-it-work/

[Malc]

I'm understanding that on a 2009 car, even tho' it has TPMS it is not compulsory to function for the MOT ...  so you're ok on that score whatever issues you have with it's electronic wizadry functionality 

Malc

[Texas]

1 hour ago, LenT said:

I think this Lexus article on the TPMS may answer these questions.

https://mag.lexus.co.uk/tyre-pressure-monitoring-system-what-is-tpms-and-how-does-it-work/

Ok, appreciate the link and it calls the two systems ‘Direct’ and ‘Indirect’ it also states that all Lexus cars after 2012 are fitted with ‘Direct’ system. But Johnlex has a 2009 ( according to his profile!

[Johnlex]

The point I’m making is I’ve put a non tpms sensor wheel on and it’s registered as if everything is ok ??

why ??

[LenT]

1 hour ago, Johnlex said:

The point I’m making is I’ve put a non tpms sensor wheel on and it’s registered as if everything is ok ??

why ??

Could it be that the system simply responds to the TPMS valves that are sending a signal?  In other words, it doesn’t recognise that one valve is missing,  but only that the signals it’s receiving are correct.

Just my guess!

I suppose you could check by deliberately deflating one of the other wheels and see if that now comes up as a fault.

[Johnlex]

1 hour ago, LenT said:

Could it be that the system simply responds to the TPMS valves that are sending a signal?  In other words, it doesn’t recognise that one valve is missing,  but only that the signals it’s receiving are correct.

Just my guess!

I suppose you could check by deliberately deflating one of the other wheels and see if that now comes up as a fault.

Yes maybe the unit is confused 

I’m told it’s behind the stereo head unit

i will deflate tyre near a pump at the petrol station to see if your theory is correct 

very strange 

[Johnlex]

On 6/9/2022 at 4:25 PM, LenT said:

Could it be that the system simply responds to the TPMS valves that are sending a signal?  In other words, it doesn’t recognise that one valve is missing,  but only that the signals it’s receiving are correct.

Just my guess!

I suppose you could check by deliberately deflating one of the other wheels and see if that now comes up as a fault.

The light has now  come on afte 100miles of driving. Must of been a glitch in the system. 
panic over everything works as it should

 

[LenT]

8 minutes ago, Johnlex said:

The light has now  come on afte 100miles of driving. Must of been a glitch in the system. 
panic over everything works as it should

 

My system has a reset button under the dash and there is a procedure for its use.

However, when I did have to reset it after having new tyres, the tyre fitter simply said “Just drive around for a bit and it’ll reset itself.”

In my case it didn’t, hence how I discovered the reset button (it was tucked away in the Manual).  But the Fitter might have been right about other systems.

Whatever, glad to hear its been resolved.

[NemesisUK]

In the RC300h (and I'd imagine other Lexus models with active TPMS) the TPMS "reset" button simply sets the current tyre pressure as the benchmark which the system checks against. When tyres are renewed and presumably inflated to the correct pressure, the system doesn't need to be "reset" as the benchmark level hasn't changed.