Its the sensor on the front nearside.
Jack up and take the front wheel off, you'll see the box, its held on with standrd cross head screws.
Remove the cover, disconnect the rod that attaches to the box, disconnect the connector to the box and remove.
Take it inside and remove the 4 screws that hold the lid on- dont shake it about as there are 3 gold springs inside it- there 'should' be some corrosion on 1 or all of the springs.
Remove the corrosion with fine sandpaper- gently- dont break, or stretch them!
Check the inside where the spring sits and clean out with some contact cleaner.
Reassemble (dont over do it when you put the lid of the box back on), and all should be working again...
Did it on my IS300 a couple of times.
J