Anyway to tell for sure if soft brakes are booster or HCU?

[mtommer]

2011 Edge. Dealerships want $160 diagnostic fee if soft brakes don't end up being an issue with the brake booster. So, is there anyway to tell for sure, or at least highly likely, whether the HCU or brake booster needs to be replaced? Aside from the soft pedal, I can apply the brakes and stop normally without much effort on the pedal. I just have to allow for the added travel before they engage. Other than the mushy pedal, I don't hear or smell anything. If the issue is likely to be the HCU, has anyone just drove their Edge as is without issue?

 

[Steve H]

When my brake booster went, the brakes were really hard to press and did nothing to help stop the car.