After having the rear axle seal replaced 3rd time, my 2004 Toyota makes a sound/noise behind the dash, drivers side, in the engine compartment. Noise is intermittent and only when braking. Hard to describe…electronic sound. Brake pedal feels like ABS system is kicking in. But no ABS light comes on. Mechanics all tell me, “when light comes on, bring it back”. Had the brake system flushed today. Still makes the noise.
Not positive about the '04 design, but I think the only brake parts on the front driver side are the power booster, master cylinder and left front caliper. A clicking sound with pedal pulsation suggests–in order of likelihood-- a warped disc, a booster malfunction or a loose caliper. You can check if your symptoms are caused by the ABS engaging by pulling the ABS fuse and seeing if the noise is still there.
It’s difficult to diagnose these things online as we can’t ride along with you…
Ask your mechanic to inspect the ABS wheel sensors. Maybe one has come unplugged. I expect that would cause a dash light to come on, but maybe not, and what you are hearing is a relay clicking due to the missing sensor signal. Easy to do, so worth a shot anyway.