Tyre pressure warning lamp

[bonerp]

keeps coming on but erratically, like every few days to weeks.

is this a sign that one (or all) needs replacing? Is there a way to tell which one is suspect or just to change the lot at next tyre change?

thanks
Paul

[X5Sport]

Have you got TPM Sensors in the wheels? I know some versions (4.8is?) have or had. Could be the battey needs replacing in them?

Our E53 3.0d only uses the ABS sensors, but that occasionally throws a light if there's a weather change. Not as often as you are seeing. It's never actually come on when there's been a real flat though

[bonerp]

abs sensors for tyre pressure? How do they work then?

Mine has the tyre pressure sensors yes. Can just batteries be purchased then?
thanks

[weirdfish]

[quote=""bonerp""]abs sensors for tyre pressure? How do they work then?

Mine has the tyre pressure sensors yes. Can just batteries be purchased then?
thanks[/quote]
ABS sensors work by detecting the rolling radius of the wheel/tyre, as a tyre deflates the rolling radius changes, as for the batteries in the valve type sensors, I think it's a bit more involved, for a start you have to know which one is playing up, and for that you need diagnostic equipment.

[CondorX5]

I *think* I saw a thread on xoutpost about this - as I recall, the battery-type sensors were on the 4.6is. My 4.8is, a 2005, has the ABS sensors, not sure if it was a date related change or if just the 4.6is had the battery-powered ones. The ABS ones also give the occasional random light - easy enough to reset once checked and possibly weather related, that's true.

Weirdfish, just to clarify - both types are "tyre pressure sensors" - one works on the rolling diameter of the wheel - ie the ABS type - if there is a change in rolling diameter, ie the wheel loses pressure, the sensor light comes on. The battery ones as said are somewhat more involved, generally viewed as a PITA if they go wrong, and are expensive little jobbies to replace, for what they are.

[x555]

[quote=""bonerp""]abs sensors for tyre pressure? How do they work then?

Mine has the tyre pressure sensors yes. Can just batteries be purchased then?
thanks[/quote]
Im pretty sure that yours will have abs wheel speed sensors (also known as pulse generators)and not the battery wheel type as only the older x's had them mate.