Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Modulator Unit
The ABS modulator consists of the inlet solenoid valve, outlet solenoid valve, reservoir, pump, pump motor, and the damping chamber. The modulator reduces the caliper fluid pressure directly. It is a circulating-type modulator because the brake fluid circulates through the caliper, reservoir, and the master cylinder. The hydraulic control has three modes: Pressure intensifying, pressure retaining, and pressure reducing. The hydraulic circuit is an independent four-channel type, one channel for each wheel.
| Pressure intensifying mode: | Inlet valve open, outlet valve closed: Master cylinder fluid is pumped out to the caliper. |
| Pressure retaining mode: | Inlet valve closed, outlet valve closed: Caliper fluid is retained by the inlet valve and outlet valve. |
| Pressure reducing mode: | Inlet valve closed, outlet valve open: Caliper fluid flows through the outlet valve to the reservoir. |
| Motor operation mode: | When starting the pressure reducing mode, the pump motor is ON. When stopping ABS operation, the pump motor is OFF. The caliper fluid is pumped out by the pump, through the damping chamber, to the master cylinder. |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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