ABS control function - GF42.45-P-3000B

MODEL 129 with ENGINE 112, 113 with CODE (472a) Electronic stability program (ESP)

MODEL 202 with ENGINE 112, 113, 604 with CODE (472a) Electronic stability program (ESP)

MODEL 208 with ENGINE 112, 113 with CODE (472a) Electronic stability program (ESP)

MODEL 210 with ENGINE 111, 112, 113, 604, 605, 606, 611, 612, 613 with CODE (472a) Electronic stability program (ESP)

MODEL 215, 220 with CODE (472a) Electronic stability program (ESP)

Braking process in normal mode

ABS pressure build-up control mode

Every ABS control starts with a normal braking process which the driver performs via the brake pedal.

The ESP control module recognizes the braking process via the stop lamp switch and decelerated wheel speeds.

The brake pressure is built up via the two switchover solenoid valves (y18 and y19) and the solenoid valves (y6, y8, y10 and y12).

This pressure build up phase can take place individually at each wheel during the ABS control process.

The pressure is reduced via the same solenoid valves during a normal braking process.

Fig 1: Identifying ABS Control Function Flow Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

ABS hold pressure control mode

The control process or valve positions shown in the example relate to the FR brake.

If a wheel tends to lock during the braking process, ABS prevents a further pressure buildup. The ESP control module introduces the hold pressure phase from the slip values of the braked wheels.

The hold pressure phase is introduced by actuating the solenoid valve (y8). The solenoid valves (y8 and y9) remain closed in this control phase, with the result that the pressure in the FR brake caliper remains constant.

Fig 2: Identifying ABS Hold Pressure Control Mode Flow Chart

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

ABS pressure reduction control mode

The control process or valve positions shown in the example relate to the FR brake.

The ESP control module introduces the pressure reduction phase from the slip values of the braked wheels.

The pressure reduction phase is introduced by actuating (opening) the solenoid valve (y9). The solenoid valve (y8) remains actuated (closed) in this control phase. During the pressure reduction phase brake fluid flows back into the high-pressure/return pump (p1) via the accumulator (11).

From there the high-pressure/return pump in the front axle brake circuit delivers the brake fluid back to the master brake cylinder against the existing pressure.

There is a silencer (10) for each brake circuit to damp delivery noise.

Fig 3: Identifying ABS Pressure Reduction Control Mode Circuit Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

	ESP control module, location/task/function		GF42.45-P-4500B
	Traction systems hydraulic unit, location/task/design/function		GF42.50-P-4000B