The noise is not predictable but occurs more on light braking. It sounds like a solenoid chattering from underneath the car. Could it be the ABS modulator? Last year the dealer bled the brakes and the noise disapeared for 6 months, but now the cold weather is here it has re-appeared. Some days it occurs a number of times and other days it doesn't occur at all. It seems to occur more during cold weather.

2011 Lexus R450h

just cap missing. How can I fix?