ETS, ABS control mode, function - GF42.35-P-3000B

MODEL 163 with CODE (212a) Electronic traction system (ETS)

Braking process in normal mode

ABS control mode - pressure build-up

Every ABS control operation starts with a normal braking process which the driver performs via the brake pedal. The ETS control module recognizes the braking process via the stop lamp switch and decelerated wheel speeds.

The brake pressure is first built up via the switchover solenoid valves (y24 and y25) and then in pressure circuit 1 (FL and RR) via the solenoid valves (y6 and y12) and in pressure circuit 2 (FR and RL) via the solenoid valves (y8 and y10).

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

Fig 1: ETS, ABS Control Mode Function (Pressure Build-Up)

ABS control mode - pressure holding

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 ETS control module initiates the pressure holding phase from the slip valves of the braked wheels.

The pressure holding phase is introduced by actuating the solenoid valve (y8). The solenoid valves (y8 and y9) are closed in this control phase; this keeps the pressure in the FR brake caliper constant.

Fig 2: ETS, ABS Control Mode Function (Pressure Holding)

ABS control mode - pressure reduction

Fig 3: ABS Control Mode - Pressure Reduction

ABS control mode - pressure reduction

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

The ETS 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 in this control phase (closed).

During the pressure reduction phase brake fluid flows back into the high-pressure/return pump (p1) via the accumulator. From there the high-pressure/return pump in pressure circuit 2 delivers the brake fluid back into the master brake cylinder against the prevailing pressure. A silencer (10) is fitted to each brake circuit to dampen delivery noise.

	ETS control mode, function		GF42.35-P-3500B
	ETS hydraulic unit, location/task/design/ function		GF42.35-P-4000B
	ETS control module, location/task/design/ function		GF42.35-P-4500A