Any ideas ? It started about 3 days ago - about 2 or 3 times it briefly appeared when pressing brake. This morning it appeared about 6 or 7 times and stayed on a lot longer.

Blimey, I thought you had sold the GS - good to see theres still one here!

Anyway, check the oil fluid level - exactly the same happened with me and it just needed topping up

Be careful, your light is coming on probably because the fluid is low, the first cause is your pads are worn out allowing the pistons to move further. Check your pads first, when fitting new pads the pistons will be pushed back and if you have previously topped up the fluid you will find the excess lying in the engine bay!

Its either brake fluid is low and perhaps the pads are worn, or there is a brake light out at the back as this uses the same circuit.

i had this problem but i solved it by replacing the front brake pads

If it's worn pads then it's just the fluid level a bit low causing the light to come on.

Funny but I thought Gary C had sold his GS too ? Anyway it's only the brake light bulb if you press the brake and the light stays on ... otherwise suggest fluid level, caliper (sticking ?) and worn pads ...

Went through all this myself over past few months, starting with brake pads, fluid etc. As it was intermittent, I dismissed the bulb being blown, but knew that when the warning light came on, my o/s brake light went out.

I ended up re-soldering the bulb holder wiring/housing and replacing the cable with new. 2 days later the warning lamp came on again!

Turned out to be a faulty bulb after all (not blown - but had a dodgy fillament connection)

Regards,
Steve J.

I had this same prob. a month ago, it was a burnt out single filament light at the back (GS300 II sport) took a long time to suss out.