ASR control mode, function - GF42.45-P-3500C

MODEL 163 with CODE (472a) Electronic Stability Program (ESP)

ASR pressure build-up control mode

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

If one of the drive wheels tends to spin when accelerating, the control module introduces the ASR pressure build-up control mode.

At the start of the control the switchover solenoid valve (y25) is switched to the "shut-off position" (closed) and the high pressure and return pump (m1) is actuated. The self-priming high pressure and return pump (p2) draws in brake fluid from the reservoir via the inlet solenoid valve (y27), open during the pressure build-up phase and the master brake cylinder.

The pressure limiting valve integrated in the switchover solenoid valve (y25) serves to limit high pressure (approx. 150 bar).

Fig 1: Circuit Diagram - ASR Control Mode, Function (ASR Pressure Build-Up Control Mode)

ASR pressure holding control mode

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

The ASR pressure holding control mode starts if a more powerful brake intervention is no longer required to prevent drive slip.

The inlet solenoid valve (y27) and solenoid valve (y8) are closed; as a result the pressure in the brake caliper cannot increase further via the high pressure and return pump (p2).

Fig 2: Circuit Diagram - ASR Control Mode, Function (ASR Pressure Holding Control Mode)

ASR pressure reduction control mode

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

The ASR pressure reduction control mode starts if the brake pressure required to prevent drive slip is too high.

The pressure reduction phase is introduced by opening the solenoid valve (y9). The solenoid valve (y8) remains closed.

The inlet solenoid valve (y27) is closed at a calculated pressure of < 60 bar in the brake calipers.

The brake fluid flows back to the reservoir via the self-priming high pressure and return pump (p2), the pressure limiting valve integrated in the switchover solenoid valve (y25) and the master brake cylinder.

Fig 3: Circuit Diagram - ASR Control Mode, Function (ASR Pressure Reduction Control Mode)

At the end of the pressure reduction phase the system pressure (approx. 150 bar) between the self-priming high pressure and return pump (p2), the switchover solenoid valve (y25) and solenoid valve (y8) is initially led to both the brake calipers of the circuit after the high pressure and return pump (m1) is switched off. This prevents the system pressure in the tandem master brake cylinder being released suddenly and reduces the noise build-up associated with this.

	ESP control module, location/task/function		GF42.45-P-4500B
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