A1e17 ABS MIL B24/2 Lateral acceleration sensor (129.076) K20/1 High-pressure/return pump relay A7/3 ASR or ETS hydraulic unit L6/1, L6/2 Left and right front axle VSS sensor L6/3, L6/4 Left and right rear axle VSS sensor N16/1 Base module S9/1 Stop lamp switch (4-pin) S12 Parking brake switch X11/4 Data link connector (DTC readout) Y61 Master brake cylinder switchover valve (129.076) On ASR only A1e21 ASR warning lamp A1e22 ASR MIL (vehicles without BAS only) A1e48 BAS/ASR malfunction indicator lamp (vehicles with BAS only) N47-1 ASR control module S76/5 ASR OFF switch
		P42.40-0292-06

P42.40-0206-01		P42.35-0212-01		P42.35-0201-01

	Location	in left of engine compartment
	Task	The ASR V/ETS hydraulic unit (A7/3) performs the control functions of the brake moment control circuit.
	Design of ASR V/ETS hydraulic unit		GF42.40-P-4000-01A
	Function of ASR V/ETS hydraulic unit		GF42.40-P-4000-02A

GF42.40-P-4000-01A

Design ASR V/ETS hydraulic unit

Models 129, 140, 170, 202, 208, 210 (except 210.08/28)

		P42.40-0289-06

GF42.40-P-4000-02A

ASR V/ETS hydraulic unit, function

Model 129, 140, 170, 202, 208, 210 except 120.08/28

		P42.40-0289-06

All switching components of the ABS and ASR or ETS systems are combined in the ASR/ETS hydraulic unit (A7/3). A 2/2-way valve for build-up/hold pressure or hold/release pressure functions is used on each wheel for control. The self-priming high pressure/return pump (p1), integrated in the hydraulic unit (A7/3), supplies pressure to the ASR or ETS. An integrated return pump (p2) is also used to return brake fluid for ABS control. The inlet pipes of the self-priming high pressure/return pump (p1) contain the inlet solenoid valve (y15) in the Bosch model and inlet valve (15) in the Teves model.

The inlet solenoid valve (y15, Bosch model) is opened once pressures of 60 bar are reached in the rear axle brake calipers during the ASR or ETS pressure build-up phase. It stays open for the time it takes to actuate the solenoid valves (y10 and y12). When pressures of > 60 bar are reached in one of the rear axle brake calipers during ASR or ETS control, the inlet solenoid valve (y15) remains open continuously. In the Teves model, the inlet valve (15) always remains open apart from when the valve is pressurized via the brake pedal with a pressure of > 0.6 bar.

Acceleration slip regulation (ASR) To achieve optimum traction if the drive torque is too high (wheel spinning) acceleration slip regulation is required. Control of torque reduction is achieved by data transfer between the control module of the built-in ASR (acceleration slip regulation) traction control system (N47-1) or ESP (N47-5) and the corresponding control module for the injection and ignition system via the CAN databus. With gasoline engines these control modules are: EFP (N4/1), LH (N3/1, N3/2, N3/3), HFM (N3/4) or ME (N3/10, N3/11, N3/12) and with diesel engines the control modules are ERE (N3/7), EVE (N3/8) or CDI (N3/9). Four cylinder gasoline engine with supercharger, 6, 8, and 12 cylinder gasoline engines: Control module EFP (N4/1) or ME (N3/10, N3/11, N3/12) reduces the throttle valve position on the throttle valve positioner (M16/1 or M16/6) with respect to the accelerator pedal position set by the driver and/or retards the ignition timing from the HFM control module (N3/4), ME (N3/10, N3/11, N3/12) or ignition control unit (N3/1).

Four cylinder gasoline engine without supercharger: The fuel feed is switched off by the HFM control module (N3/4). Diesel engine: The quantity of fuel is reduced by the ERE control module (N3/7), EVE (N3/8) or CDI (N3/9). A continuous check takes place in the ASR or ESP control module (N47-1 or N47-5) whether, e.g. because of suddenly improved road adhesion, the control function can be canceled so as to permit the drive torque desired by the driver via the accelerator pedal as soon as possible.

MSR engine friction torque control (not with 4 cylinder gasoline engine without supercharger) If slip occurs on the drive wheels when the accelerator position is reduced, this is detected by the ASR or ESP control module (N47-1 or N47-5). Four cylinder gasoline engine with supercharger, 6, 8, and 12 cylinder gasoline engines: The signal (raising of throttle valve) is transmitted to the EFP or ME control module (N4/1) (N3/10, N3/11, N3/12) via the CAN databus. The calculated throttle valve opening is controlled by the control module (N4/1, N3/10, N3/11, N3/12) via the throttle valve positioner (M16/1).

Diesel engine: The signal (increase fuel quantity) is transmitted via the CAN databus to the ERE (N3/7), EVE (N3/8) or CDI (N3/9) control module. The fuel quantity injected is increased by the control module. With this information, the drive torque can be changed so that no slip occurs at the drive wheels. This improves the lateral stability of the vehicle. This process occurs without driver information (warning lamp A1e21 or A1e41).