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Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Mon Nov 11, 2019 3:55 am
by littlescrote
Do we know that the wheel sensors actually measure and transmit pressure, or are they just a binary switch that is either above a pressure or below it?

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Mon Nov 11, 2019 4:05 am
by Regulo
The fact that you can re-calibrate the trigger point for a warning suggests they're not a simple on-off switch, but transmit real-time variable readings.

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Mon Nov 11, 2019 10:25 am
by STS134
littlescrote wrote:Do we know that the wheel sensors actually measure and transmit pressure, or are they just a binary switch that is either above a pressure or below it?
The sensors actually measure pressure. And the transmitters transmit pressure (as well as temperature). The system uses FSK modulation and 100 kHz bandwidth to transmit its data at either 315 MHz or 433 MHz. http://i56578-swl.blogspot.com/2017/08/ ... -tpms.html

This guy created a software-defined radio that can see both values:
https://www.youtube.com/watch?v=bKqiq2Y43Wg

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Tue Nov 12, 2019 8:54 am
by littlescrote
STS134 wrote:The sensors actually measure pressure. And the transmitters transmit pressure (as well as temperature). The system uses FSK modulation and 100 kHz bandwidth to transmit its data at either 315 MHz or 433 MHz. http://i56578-swl.blogspot.com/2017/08/ ... -tpms.html

This guy created a software-defined radio that can see both values:
https://www.youtube.com/watch?v=bKqiq2Y43Wg
Interesting but not PHEV specific is it? You are assuming (probably correctly given that there are very few different standards for these things) that the OEM sensors do the same.
Regulo wrote:The fact that you can re-calibrate the trigger point for a warning suggests they're not a simple on-off switch, but transmit real-time variable readings.
Can you? Where? Or is that dealer (or ETACS) only?

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Tue Nov 12, 2019 10:15 am
by Regulo
Lifted from a previous post on here:

Reset of low tyre pressure
warning threshold

The threshold is set based on the tyre pressure which the reset function is executed by following procedure.

1. Operate the multi-information display switch to switch the information screen to the menu screen.
2. Lightly press the multi-information display switch to select “ ” (reset of low tyre pressure warning threshold).
3. Hold down the multi-information display switch for about 3 seconds or more, the buzzer sounds.
4. The warning lamp start flashing slowly.
5. Drive for a while. The reset is completed if the warning lamp goes out.


I presume (it's not clear from the text), that this will reset the threshold as a set amount below whatever the pressure in the tyres is when this reset procedure is done. If that makes any sense? So the sensors must be transmitting a value that the software interprets as a "starting point" for the warning function. You can't actually set a value of pressure, just a base point, from which the software calculates pressure drop. I've never fiddled with this, so I can't say whether this is actually how it works or not.

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Wed Nov 13, 2019 4:22 am
by littlescrote
That makes sense, if you can do that then they must be transmitting pressure.

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Wed Nov 24, 2021 3:17 am
by oscarmax
I regularly check and amend my tyre pressure, however due to commitments I have not check the pressure since the end of September. Front tyre down to 28 psi rear down to 33psi (Rear tyre pressure normally set to 38 psi due to carrying a heavy Motability scooter), I don't have the confidence or ability to mess with the tyre menu settings so I brought one of these, I have an older version on our caravan for the last 6 years it simple/ easy and extremely accurate.

I decide to buy one off these £98.00 including my discount, easy to set up just fit the sensors in place of the tyre valve cap and the system does the rest, I now can monitor both the tyre pressure and temperatures.

https://www.tyrepal.co.uk/product/kit-b ... so-sensors

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Wed Nov 24, 2021 8:59 am
by jaapv
I have the Steelmate system for that.

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Thu Nov 25, 2021 3:56 am
by littlescrote
Claiming to be able to measure any meaningful temperature at the valve cap is a joke.

Re: TPMS on the PHEV - no pressures, what a joke!

Posted: Thu Nov 25, 2021 1:14 pm
by AndyInOz
I fitted internal tyre pressure and temperature sensors to mine.

(A little solar powered unit on the dashboard gives a constant display of temperature and pressure for each tyre while the car is in motion, or if you press a button on the side of the dashboard unit.)

I had the steelmate valve top type for a while and found them to be excellent, they gave me early warning of a slow leak which meant that the tyre could be repaired before the tek screw had done too much damage.

I only replaced them because I was sick of removing them every time I wanted to put air in the tyres.