Question about tyre pressure monitors 08 C5X7

[aerodynamica]

I've had no end of trouble with tyres lately and keeping them inflated and it turns out the issue is with the TPMS valves leaking due to corrosion. Chain tyre place said they didn't have those type of tpms seals etc in stock so tried to seal them but it failed with one of two new tyres going down overnight. Best thought was to buy a set of chinese tpms replacements as one of the four originals doesn't connect to the system anyway and I hoped the replacements can work... long shot possibly. Anyway, the new tpms has sealed properly and the tyre stays up now. Plan is to replace all the others with these new ones and hopefully reprogram them.

I only have the old lexia 3 diagnostic that recognises the tpms units and shows faults if they have them but I do not think i can program the new units with it. I was wondering if anyone knows if it's possible to change the way it programs the tpms valves so that they are no longer specific location , Front Left etc as its annoying when changing tyres around that the locations are wrong. They're already wrong right now. I believe some cars have a tpms that simply says 'A tyre is deflated '. It's that possible for the C5x7?

Secondly, anyone in the Glasgow area have the diagbox system that might be able to program mine?

[GiveMeABreak]

Hi Graeme

Unfortunately not, the system is as it is, and programming is required whenever new TPM sensors are replaced or the wheels are rotated. You can also programme a second set of these (for when people have a spare set of wheels for winter).

The later system you mention is called an 'Indirect' TPMS system, where there are no actual sensors on the wheels, ECU or aerial - it's all done by the wheel speed sensors and the ESP ECU by analysing any change in the diameter of the wheels or in the physical behaviour of the tyres to determine a puncture or total deflation. Most of these don't have a location system, so you would have to locate the actual wheel with the low pressure if not obvious yourself.

I refer to these systems in my recent post here:

viewtopic.php?p=815734#p815734

[aerodynamica]

Thanks Marc, yes o did kind of expect that. We'll it's fine I'll just go with plan A and that's to simply replace the remaining ones and reprogram them hopefully

[GiveMeABreak]

Hopefully they will be compatible - the originals are made by Siemens, so you've had a good 16 years out of them (or the car has at least)

[aerodynamica]

It's not bad. Actually looking at the old tyre sensor it seems to have worn the years well. I notice that the electronic potting/ resin used to enclose the electronic board and presumably the battery is in good nick except for one area that a bit soft and 'squeezy' and I suspect that the location of the battery. Although this particular unit was one of the three which still functioned, just that it leaked air. The Chinese replica items look identical so I hope they're good. Like that they actually have electronics in there!

[GiveMeABreak]

Good point, that always helps!