Bosch 9.0 ESP / ABS info;

[Novexx]

This is as fitted to an Audi B9 S5, but I think the same system is pretty commonplace.

A while back the car was indicating brake & related warnings caused by a failed brake servo pressure sensor, this was replaced & all is currently good, but;

My understanding is that the failed servo sensor causes the ABS to operate every time the brakes are used (pump attempting to increase apparently low brake pressure) & that after a certain number of operations the ABS module goes into fault mode & requires replacement.

Does anyone know if this is as simple as a total count of pump operations, including "normal" ABS operations? If that is the case can the number of ops be retreived from the car / is the limit know.

I'm now wondering if I have a limited number of ABS operations left before a £3K repair bill.


Thanks.

[stevieturbo]

Novexx said:

My understanding is that the failed servo sensor causes the ABS to operate every time the brakes are used (pump attempting to increase apparently low brake pressure) & that after a certain number of operations the ABS module goes into fault mode & requires replacement.

Sounds extremely odd....where has this information come from ?

[Novexx]

stevieturbo said:

Sounds extremely odd....where has this information come from ?

Deduction I guess.

The pressure sensor is a pretty common failure on VAG vehicles & it's a certainty that if left for any period of time the ABS module will consequently fail, advice from dealers than can be bothered to be helpful is replace the sensor ASAP or it will cost you a module.

If the pressure sensor is faulty, a "brake servo restricted" warning is shown & the ABS pump is clearly operating (it can be heard & felt) on anything but a very gentle press on the brake pedal, so I'm guessing that after a specific number of operations in this mode, the module faults.

Edit:- A bit more searching & it looks like the "C123EF0 hydraulic brake servo limit reached" error is logged after a certain number of ops & it's a permanent error that can only be resolved by module replacement or rebuild.

Still don't know if it's only operations in this scenario that are logged / counted or all ABS operations & don't know if the limit & current count are available.