Tyre pressure sensor and alarm

[WillBarna]

Well, many thanks all, for your detailed replies and photos.
I will try bypassing the switch and see if that helps.
But I've tried every combination of pressing the button and the light remains on, whatever I do.
Oh well.

[Flash2]

Off the top of my head...on the switch connector you'll probably find a grey wire (illumination supply), a brown (earth) and another wire (don't know colour). The other wire is the signal wire leading to the ECU. You want to disconnect the switch and use a thin piece of wire to bridge the brown and the signal wire together. Leave the bridge piece in for a few seconds to simulate holding the button down and see if the warning resets.

Jim.

[RichardSEL]

Before shorting anything to anything else (there's the button illumination supply there too as Flash2 says) see whether there's any more info on Bold2's site as to what wire colour wire does what. I don't have ELSA to see the circuit for wire colours. They sell this loom for an aftermarket fitting of the SET switch:
TPMS Loom.jpg

If you safely want to check the switch operation, better you disconnect it and with a multi-meter set to Ω range prod around for a short continuity that's only there when the button's pressed

[Flash2]

You can do the multimeter test on the switch if you prefer that method. Disconnect the switch and connect your ohmmeter between pins 4 & 5 on the back of the switch. Now press the button and see if you get a "short circuit".
I prefer the bypass method of testing because it's easier, quicker and will actually achieve the goal of resetting the warning if the switch is faulty...but each to their own.

From the circuit diagram the switch connector wiring is : (Pin3) Grey - illumination supply, (Pins 5&6) 2X Brown - earth, (Pin4) Black/White - signal wire to ABS ECU.

Jim.