S400-851-877-7 Genuine Wabco Hydraulic Power Brake HCU With Module 10 Coil ATC

1. Prevents wheel lock (ABS)
If you brake hard, the system rapidly pulses brake pressure so the wheels don’t lock up—helping you keep steering control instead of skidding.

2. Improves traction
If a wheel starts slipping (like on rain, snow, or gravel), it adjusts braking to regain grip.

3. Stabilizes the vehicle (ESC)
If the car starts to slide or spin, it can apply braking to specific wheels automatically to help keep you on your intended path.

4. Balances braking force
The “10-coil” setup means multiple valves are controlling pressure across different channels, allowing fine-tuned braking at each wheel, not just all-or-nothing braking.

• ABS light stays on
• Traction control light or stability control light
• Sometimes a general brake warning light

Loss of safety features

• ABS stops working (wheels can lock during hard braking)
• Traction control disabled
• Stability control unavailable

The car will still brake, but you’ve lost the “smart” assistance.

Unusual brake behavior

• Brake pedal may feel:
  • Harder than normal
  • Spongy or inconsistent
• Longer stopping distances in slippery conditions
• In rare cases, uneven braking between wheels

Strange noises

• Clicking, buzzing, or grinding sounds from the HCU area (usually when braking or when the system tries to activate)

Electronic issues / codes

• Diagnostic scan shows ABS or HCU-related trouble codes
• Communication errors between the module and the car’s computer