IVS 360 support offers live repair guidance and remote programming services to help workshops fix complex vehicles safely and fast. All solutions come with live repair guidance from IVS 360™ OEM brand-specific master technicians.
Damon Howes, VAG Master Technician at Opus IVS helped a customer with an Audi A4 who fixed and cleared a vacuum sensor fault, but the vehicle continued to display fault code C123EFO (hydraulic brake booster).
Here is the guidance that Damon provided to repair the fault:
Make/Model: Audi A4
Customer information provided:
(C123EF0) Hydraulic brake boost limit value exceeded.
(P050F) Brake Assist Vacuum Too Low.
(C123EFO) hydraulic brake booster, limit reached 263936.
(C11ECO4) brake booster pressure sensor.
Fault codes C123EFO hydraulic brake booster limit value reached.
C11EC04 brake booster pressure sensor faulty.
Work already carried out:
Fixed vacuum sensor fault and cleared but C123EFO still present (static).
The fault starts as a brake servo vacuum sensor fault.
As soon as this fault is recorded, the ABS system uses an accumulated source of pressure to work/boost the Brake Assistance, once the accumulated pressure drops (brake pedal activated several times) the ABS system has no way to restore system pressure!
The ABS unit (complete) must be replaced. (New ABS units sometimes have Component Protection).
The job of the Bosch ABS 9 has changed slightly, in the fact that the ABS is now capable of generating additional braking force, if the servo does not seem to be able to generate desired assistance. This is known as “Optimised hydraulic brake servo” (OBBS).
If the driver ignores the yellow “!” on the Instrument Panel Cluster, this could become a red “!” which would result in requiring a completely new ABS module.
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