ASC control mode, function - GF42.45-P-3500TX

MODEL 211, 219.3 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version 

MODEL 211, 219.3 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version 

Fig 1: ASC Control Mode Function Diagram - Pressure Buildup

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Acceleration slip regulation (ASR) control mode 

ASR control mode - pressure buildup 

The control process shown in the example and the valve positions refer to the right rear wheel brake (RR).

The control process shown in the example and the valve positions refer to the right rear wheel brake (RR).

If one of the drive wheels tends to spin when starting off or accelerating, on an oversteering vehicle first the drive torque is reduced by the engine control unit in order to increase the lateral stability of the driven rear wheels. If the instability which is starting cannot be prevented as a result, then the ESP control unit (N47-5) introduces the ASR closed-loop operation "Pressure buildup" via the SBC control unit (A7/3n1).

The left front separation valve and right front separation valve y1 and y2 and the rear axle balance valve y4 are closed at the start of the ASR control. The right rear outlet control valve remains closed. The right rear inlet control valve is opened.

The pressure from the pressure reservoir (3) can now be built up at the rear right brake caliper.

Fig 2: ASC Control Mode Function Diagram - Pressure Holding

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

ASR-closed-loop operation, pressure holding 

The control process shown in the example and the valve positions refer to the right rear wheel brake.

If to prevent drive slip a more powerful intervention into the braking system is no longer required, then the ASR-closed-loop operation "Pressure holding" starts.

The right rear inlet control valve is closed. As a result the pressure from the pressure reservoir (3) cannot be increased in the brake caliper of the right rear wheel brake.

Fig 3: ASC Control Mode Function Diagram - Pressure Reduction

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

ASR control mode - pressure reduction 

The control process shown in the example and the valve positions refer to the right rear wheel brake.

If the brake pressure required to prevent brake slip is too high, then the acceleration slip regulation closed-loop operation "depressurization" starts.

The pressure reduction phase is introduced by opening the right rear outlet control valve. The right rear inlet control valve and rear axle balance valve remains closed.

The returning brake fluid flows via the return pipe to the brake fluid reservoir.