ABS Hydraulic Modulator
The valve block and pump the anti-lock system uses to release and reapply brake pressure at individual wheels, usually with the control module bolted to it as one assembly. Worth being clear about what it does: it can only release pressure the driver has already applied, so it sits on top of an ordinary hydraulic braking system rather than replacing it — losing it costs anti-lock, stability and traction control, not braking. Because module and hydraulics are one unit, replacement is expensive and often requires programming, which is why its power, earth, connector and bus wiring are worth exhausting first.
Also known as: abs pump, abs module, abs unit, hydraulic control unit, hcu, modulator, abs block
Referenced by 69 codes
Codes involving this component (69)
- C0012 Left Front Hydraulic Release Too Long Stop driving High
- C0016 Right Front Hydraulic Release Too Long Stop driving High
- C001A Left Rear Hydraulic Release Too Long Stop driving High
- C001E Right Rear Hydraulic Release Too Long Stop driving High
- C055F BSCM/EBBC Hydraulic Unit Performance High
- C0582 Brake Booster Motor A Phase U-V-W Circuit Range/Performance High
- C058A Brake Booster Motor A Position Sensor Circuit Range/Performance High
- C058E Brake Booster Motor B Position Sensor Circuit Range/Performance High
- C05A4 Wheel Speed Sensors Supply Circuit Low High
- U0121 Lost Communication With Anti-Lock Brake System (ABS) Control Module A High
- U0122 Lost Communication With Vehicle Dynamics Control Module High
- U0128 Lost Communication With Park Brake Control Module High
- U0129 Lost Communication With Brake System Control Module A High
- U0315 Software Incompatibility With Anti-Lock Brake System (ABS) Control Module High
- U0318 Software Incompatibility With Brake System Control Module A High
- C0001 TCS Control Channel A Valve 1 Moderate
- C0002 TCS Control Channel A Valve 2 Moderate
- C0003 TCS Control Channel B Valve 1 Moderate
- C0004 TCS Control Channel B Valve 2 Moderate
- C0010 Left Front Inlet Control Moderate
- C0011 Left Front Outlet Control Moderate
- C0014 Right Front Inlet Control Moderate
- C0015 Right Front Outlet Control Moderate
- C0018 Left Rear Inlet Control Moderate
- C0019 Left Rear Outlet Control Moderate
Other components in Braking, Steering and Suspension
- Brake Booster 92
- Wheel Speed Sensor 72
- Brake Pressure Sensor 42
- Tone Wheel 39
- Yaw Rate Sensor 28
- Brake Pedal Position Sensor 23
- Steering Angle Sensor 21
- Electric Power Steering Motor 13
- Ride Height Sensor 7
- Tyre Pressure Sensor 5
- Electric Park Brake Actuator 4
- Park Brake Control Module 4
- Air Suspension Compressor 3
- Brake Fluid Level Sensor 2
- Brake Pad Wear Sensor 2
- Traction Control Switch 2
- Brake Caliper 1
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Working on this component
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about ABS Hydraulic Modulator.