brake boost pressure sensor

[Embram]

I have Brake system service now light on 2014 tourneo custom.
codes C0047:1e-OB AND UO4O1:68-48. This points to either faulty brake boost pressure sensor or wiring problem. When back probing the 3 wires going to the sensor the brown/purple wire shows 3.72V. The yellow/orange wire show 5.04V. The white/blue wire show 4.25V. This is with the engine ticking over. I am lead to believe that the brown/purple wire should be earthed. Any info on this would be appreciated especially which wire should be the earth.

[metalworker0]

The questions are;

Does the brake system feel like it is not assisted and you have to use a lot of force on the pedal to stop .. if so look at the vacuum pipes or vacuum pump or booster. (note the boosters have an air filter on the inside of the bulkhead, they can and do get clogged - dog hair etc

Testing for, if you still have assistance ... press on brake pedal -- start engine .. your foot should go down, the booster should hold enough vacuum for a few pushes on the brake.

Pressure sensor testing
Will leave that to others to explain .. if they don't add to this, will look it up and come back, besides you have the above tests to do first.


all the best.mark

[Embram]

Thanks for the input. The pedal does go down a bit when started with my foot on the brake. Takes about 4 or 5 presses to release vacuum when turned off. The brake works fine. Im trying to work out if its a faulty sensor or the wiring. If the service brake warning did not show up on the dash you would never know.

[Embram]

UPDATE. after checking another custom wiring to the brake boost pressure sensor it turns out the White with blue trace wire is the earth. connected my white/blue wire from the sensor to earth and the brake service warning light is off.