C5 X7 tyre pressure sensors

[RichardW]

That's the MK2 C4Pic from 2013 on - our new one has that system, not had to reset it yet....

[GiveMeABreak]

It seems that it has to rely on the system being reinitialised every time the pressures are adjusted and that the tyres have been filled to the correct pressures to start with; and reset after every warning once the tyres are at the correct pressures...

The under-inflation alert can only be relied on if the reinitialisation of the system has been done with the pressures in the four tyres correctly adjusted.
The under-inflation detection system does not give a warning if a pressure is incorrect at the time of reinitialisation.

[osx]

What about these? Not metallic but have the screw to attach the sensor.

https://www.ebay.co.uk/itm/253691960232

[GiveMeABreak]

Are you serious? This is more Chinese junk and nothing at all in common with the C5 TPMS system, past, present or future.... despite their ridiculous claims of compatibility

I suspect what they actually mean is the valve part only - which is therefore not a sensor and as they obviously don't know the difference I would steer clear.

[osx]

Yes, only the valve part. Can be used with existing sensors and replace a valve that is corroded or worn.

[GiveMeABreak]

Thought as much

[XUD9]

Guys, I just activated the TPMS with Lexia in BSI menus on my 2012 X7 (facelift) . I don't have valve sensors, so I chose "Indirect type" .
Now when pressing Check button, there is additional screen with tire pressure information (displaying: Pressures OK) .

I tried to reduce the pressure of rear right tire, with 0.5bar (from 2.4bar to 1.9bar) . 5km later, with speed about 100km/h, driving on a straight road - no indication. Again: Pressures OK.

Of course I checked all tires before my little experiment - the difference was 0.5bar between the rear one and the rest.
So, can I make it work, or there is different type of ECU for ABS/ESP? Or 0.5bar is not enough for reducing the radius of the wheel?

[GiveMeABreak]

Indirect and direct are 2 different systems.

Bespoke indirect system uses the engine ECU, ABS/ESP ECU and the wheel speed sensors to calculate if there is a pressure loss - it does not tell you the pressures. This system was never fitted tot he X7, so that won't work.

The system fitted tot he X7 was DIRECT TPMS which uses wheel Tyres Pressure sensors and a separate ECU fitted to the rear of the vehicle. The system monitors and polls the sensors at regular intervals. Enabling the system is useless if you do not have the actual equipment fitted.....

[XUD9]

So it will not work...

The main disadvantage of the "indirect type" is, that it can't detect if all tires are flat, or over inflated (same pressures for 4 tires, both cases) .
It's strange that it wasn't fitted as an option (indirect type) It's not something complicated as hardware - just a couple of additional lines in the code of the ECU...

[GiveMeABreak]

...and the BSI and the instrument panel ECU and the Engine ECU etc. etc.

TPMS has become a legal requirement in EU countries from 2014, so they looked to save money of course as having direct TPMS cost a lot more.