Curiosii for ever!: Car repair manuals for everyone.
Home >> Mercedes Benz Truck >> 2003 >> G 55 AMG (463.246) V8-5.5L (113.982) >> Repair and Diagnosis >> Brakes and Traction Control >> Description and Operation >> GF42.30-P-2000F ABS Braking Torque Control Circuit, Function

GF42.30-P-2000F ABS Braking Torque Control Circuit, Function




GF42.30-P-2000F ABS Braking Torque Control Circuit, Function
MODEL 463.243 /244 /246 /247 /249 /250 /254 ## as of 127357 as of 1.9.01 up to 31.5.12, 463.270 /271 up to 31.5.12, 463.309 /322 /323 /332 /333 ## as of 127357 as of 1.9.01 up to 31.5.12
- with CODE (BB3) Electronic Stability Program (ESP)
MODEL 463.248 ## as of 127357 as of 1.9.01 up to 31.5.12
- with CODE (BB3) Electronic Stability Program (ESP)
- except CODE (979) Special protection version





"Pressure build-up" function at all wheels

5a Right front wheel brake
A7/3 Traction system hydraulic unit
A7/3p1 Front axle high pressure and return pump
A7/3y6 Left front axle solenoid valve, hold pressure
A7/3y7 Left front axle solenoid valve, reduce pressure
A7/3y8 Right front axle solenoid valve, hold pressure
A7/3y9 Right front axle solenoid valve, reduce pressure
A7/3y18 Front axle switchover valve
A7/3y22 Front axle inlet solenoid valve
A7/7 BAS brake booster
A7/7y1 BAS solenoid valve
B34 ESP brake pressure sensor

b Brake pressure





"Hold pressure" function

Shown on right front wheel brake

5a Right front wheel brake
A7/3 Traction system hydraulic unit
A7/3p1 Front axle high pressure and return pump
A7/3y6 Left front axle solenoid valve, hold pressure
A7/3y7 Left front axle solenoid valve, reduce pressure
A7/3y8 Right front axle solenoid valve, hold pressure
A7/3y9 Right front axle solenoid valve, reduce pressure
A7/3y18 Front axle switchover valve
A7/3y22 Front axle inlet solenoid valve
A7/7 BAS brake booster
A7/7y1 BAS solenoid valve
B34 ESP brake pressure sensor

b Brake pressure





"Pressure reduction" function

Shown on right front wheel brake

5a Right front wheel brake
A7/3 Traction system hydraulic unit
A7/3p1 Front axle high pressure and return pump
A7/3y6 Left front axle solenoid valve, hold pressure
A7/3y7 Left front axle solenoid valve, reduce pressure
A7/3y8 Right front axle solenoid valve, hold pressure
A7/3y9 Right front axle solenoid valve, reduce pressure
A7/3y18 Front axle switchover valve
A7/3y22 Front axle inlet solenoid valve
A7/7 BAS brake booster
A7/7y1 BAS solenoid valve
B34 ESP brake pressure sensor

b Brake pressure
e Reduced pressure

1 Capture and process sensor signals and status of switches
The ESP and BAS control module (N47-5) reads in and evaluates electric input signals from the following system components.
1.1 Wheel rpm sensors (L6/1 to L6/4)
Continuously compares the conditioned actual values for the wheel rpm signals with each other and with the specified values as the driver applies the brakes.
The ESP and BAS control module (N47-5) uses the slip values of the braked wheels calculated from these comparisons to determine if one or several wheels are starting to lock up.
1.2 Stop lamp switch (S9/1)
Detect and evaluate the position of the dual contact switch (NO contact and NC contact) when the driver applies the brake, i.e. detect when the driver presses the brake pedal.
1.3 ESP brake pressure sensor (B34)
Detect the brake pressure and calculate the wheel braking forces (longitudinal forces).
Detect when the driver presses the brake pedal.
2 Activation and deactivation of the ABS braking torque control
^ The ABS control mode may be activated when the driver presses the brake pedal. The ABS control mode is activated as soon as the ESP and BAS control module (N47-5) detects that one or more wheels are beginning to lock up.
^ The ABS control mode is deactivated when the driver releases the brake pedal or when control is no longer necessary (e.g. if the driver reduces the brake pressure applied to the brake pedal or when the wheels no longer lock up).
3 Brake pressure build-up
The brake pressure build-up procedure for brake application when the ABS control mode is active consists of three control phases - pressure build-up, hold pressure and pressure reduction.
3.1 Pressure build-up
The "pressure build-up" control phase begins when the driver presses the brake pedal and ends when the "hold pressure" phase begins. The "hold pressure" phase begins when the ABS control phase is activated.
3.2 Hold pressure
The "hold pressure" control phase begins as soon as one or several wheels start to lock up.
It is then no longer possible to increase the brake pressure further.
3.3 Pressure reduction
If the brake pressure available during the "hold pressure" phase is too high, the "pressure reduction" control phase begins.
4 Actuation of the traction system hydraulic unit (A7/3) solenoid valves
The traction system hydraulic unit (A7/3) is the electronic mechanical actuator in the braking torque control circuit.
The following example describes the actuation of the traction system hydraulic unit (A7/3) solenoid valves during the three control phases at the right front axle brake (5a).
The relevant solenoid valves of the front and rear axle brake circuit would be actuated in the same way at the other wheel brakes.
4.1 Front axle switchover valve (A7/3y18)
Same function as rear axle switchover valve (A7/3y19).
^ Pressure build-up, hold pressure, pressure reduction
--> Not actuated and therefore allows the pressure to be increased and remains in the flow position during the entire control phase.
4.2 Front axle inlet solenoid valve (A7/3y22)
Same function as rear axle inlet solenoid valve (A7/3y23).
^ Pressure build-up, hold pressure, pressure reduction
--> Not actuated during the entire control phase and remains in the lock position (basic position).
4.3 Front axle high pressure and return pump (A7/3p1)
Same function as rear axle high pressure and return pump (A7/3p2).
^ Pressure build-up, hold pressure
--> Is not actuated and does not pump brake fluid.
^ Pressure reduction
--> Actuated and pumps brake fluid against the existing brake pressure via the damper (10) and the open front axle switchover solenoid valve (A7/3y18) back into the reservoir.
The damper muffles the pumping sound.
4.4 Left front solenoid valve, hold pressure (A7/3y6)
Same function as:
Right front solenoid valve, hold pressure (A7/3y8)
- Left rear solenoid valve, hold pressure (A7/3y10)
- Right rear solenoid valve, hold pressure (A7/3y12)
^ Pressure build-up, hold pressure, pressure reduction
--> Is not actuated and remains in flow position. The same brake pressure is therefore applied at the left front wheel brake (5b) as at the right front wheel brake (5a).
4.5 Right front solenoid valve, hold pressure (A7/3y8)
Same function as:
- Left front solenoid valve, hold pressure (A7/3y6)
- Left rear solenoid valve, hold pressure (A7/3y10)
- Right rear solenoid valve, hold pressure (A7/3y12)
^ Pressure build-up
--> Not actuated, remains in flow position and therefore allows pressure build-up in the right front wheel brake (5a).
^ Hold pressure, pressure reduction
--> Actuated after successful pressure build-up and switches to lock position.
4.6 Right front solenoid valve, reduce pressure (A7/3y9)
Same function as:
- Left front solenoid valve, reduce pressure (A7/3y7)
Left rear axle solenoid valve, reduce pressure (A7/3y11)
- Right rear solenoid valve, reduce pressure (A7/3y13)
^ Pressure build-up, hold pressure
--> Not actuated, is in lock position and brake pressure is applied.
^ Pressure reduction
--> Actuated, switches to flow position and allows pressure reduction in right front wheel brake (5a).




pro multis · Curiosii