Abs Traction Control Hydraulic Circuit, Solenoid Valve, And Shuttle Valve Function (Abs With Traction Control)

Fig 1: Hydraulic Circuit - Traction Control Mode

Courtesy of DAIMLERCHRYSLER CORP.

1 - OUTLET VALVE

2 - PUMP PISTON

3 - PUMP/MOTOR (ON)

4 - LOW PRESSURE ACCUMULATOR PRESSURE

5 - LOW PRESSURE ACCUMULATOR

6 - NORMALLY CLOSED VALVE (MODULATING)

7 - TO WHEEL BRAKE (WHEEL SPINNING)

8 - NORMALLY OPEN VALVE (MODULATING)

9 - NORMALLY OPEN TC (ASR) VALVE ON (REGULATING)

10 - FROM MASTER CYLINDER

11 - HYDRAULIC SHUTTLE VALVE

12 - CONTROLLED WHEEL PRESSURE

13 - SUCTION VALVE

14 - PUMP INTERSTAGE PRESSURE

15 - NOISE DAMPER CHAMBER

16 - MASTER CYLINDER PRESSURE

17 - PUMP PRESSURE

The hydraulic diagram shows the vehicle in the traction control (TC) mode. See Fig 1. The diagram shows a drive wheel is spinning and brake pressure is required to reduce its speed.

The normally open TC (ASR) valve is energized to isolate the brake fluid being pumped from the master cylinder and to isolate the driven wheel.
The normally open TC (ASR) valve bypasses the pump output back to the master cylinder at a fixed pressure setting.
The normally open and normally closed valves modulate (build/decay) the brake pressure as required to the spinning wheel.