Brake Fault

[AudiA8Quattro]

My 2007 Sharan comes up with 'Brake Fault - Check Manual' under heavy braking. This only comes up intermittently.
The fluid level looks fine, there are no leaks at the calipers. I have put it on VAG com, ABS brakes show no faults.
The brakes work absolutely fine, ABS cuts in when it should. I can't get the warning to come up again, it has come up a few times now randomly.
There is separate warning for fluid level, so what does this warning mean?

[topher]

check the wiring for the pad level sensor

[AudiA8Quattro]

Thanks mate.
Forgot to mention as well front pads are still ok. There is separate warning for brake pads, but this isn't lit.
I've tried googling, but there doesn't seem to be a definition.
Is there anything else that would display Brake Fault?

[Gti_Jamo]

Possible intermittent fault with the brake light switch maybe? I'm sure they are connected up to the ecu. Worth checking out if you can't find anything obvious wrong with the abs.