IMPACT 4.07.
172 06/10/2023
Chassis ID Path
5631/Description, Design and function//Modulators, component description
Model Identity
FM (4) 158943979
Publish date ID/Operation
27/10/2021
Modulators, component description
Modulators
Overview
Electro pneumatic modulator
Single channel modulator
Dual channel modulator
Brake valve, ABS
Trailer control modulator
Related information
Modulators
Overview
The EBS (Electronically controlled Brake System) consists of the following types of modulators and
valves for the brake function:
Modulators
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
1 Electro pneumatic modulator, single channel
2 Electro pneumatic modulator, dual channel
3 Footbrake valve modulator
4 Brake valve, ABS (Anti-lock Braking System)
5 Trailer control modulator
Electro pneumatic modulator
The modulator electronically controls the brake pressure in the connected brake cylinders on request
from the EBS control unit.
Wheel speed sensors and brake lining wear sensors are connected to the modulator . The measured
sensor signals from both internal and external sensors are processed in the modulator and then
passed on to the EBS control unit via CAN (Controller Area Network) communication for further
evaluation.
If the brake system loses its electronic control there is the pneumatic backup system controlled by
the footbrake valve in the footbrake valve modulator.
The modulators are available in three versions:
● Single channel modulator
● Dual channel modulator - basic
● Dual channel modulator- full
The modulator consists of die cast housing, relay valve, filter, silencer, solenoid valves, pressure
sensor, pneumatic ports and electrical connectors.
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
Single channel modulator
Overview
1 Air inlet from air tank
2 Air outlet to brake cylinder
3 Exhaust, via silencer
4 Backup circuit
5 Lining wear sensors (black code)
6 Wheel speed sensor (grey code)
7 Wheel speed sensor (black code)
8 CAN B, supply, GND (green code)
Single channel modulator, schematic diagram
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
RLV Relay valve
Fi Filter
SD Silencer
IV Solenoid inlet valve for electronic brake pressure control
OV Solenoid outlet valve for electronic brake pressure control
BV Solenoid valve for backup circuit
PS Pressure sensor
LWS Lining wear sensor
WSS Wheel speed sensor
The single channel modulator is intended for the following single axles:
● Single front axle
● Pusher axle
● Tag axle.
The single channel modulator provides both brake cylinders with the same air pressure. In the front
brake system, the modulator is combined with two ABS valves.
Dual channel modulator
Overview
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
1 Air inlet from air tank
4 Backup circuit
21 Air outlet to brake cylinder
22 Air outlet to brake cylinder
3 Exhaust, via silencer
5 Lining wear sensors (black code)
6 Wheel speed sensor (grey code)
7 Wheel speed sensor (black code)
8 CAN B, supply, GND (green code)
9 Lining wear sensors (grey code), 2C EPM Full
10 Wheel speed sensor (brown code), 2C EPM Full
11 Wheel speed sensor (green code), 2C EPM Full
12 Connector not in use
Dual channel modulator, schematic diagram
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
RLV Relay valve
Fi Filter
SD Silencer
IV Solenoid inlet valve for electronic brake pressure control
OV Solenoid outlet valve for electronic brake pressure control
BV Solenoid valve for backup circuit
PS Pressure sensor
LWS Lining wear sensor
WSS Wheel speed sensor
The dual channel modulator is used for the following:
● Rear braking system
● Front braking system for dual front axles.
The dual channel modulator is used on one or two driving rear axles and can vary the brake
pressure to each side. This modulator is also used on the front brake system with dual front axles.
The dual channel modulator is available in two versions:
● The full version is used for the front braking system with dual front axles (FAA20) and the rear
braking system with two driving axles for lighter axle loads (RAL17, RAL21). This modulator has
sensor inputs for all four wheels.
● The basic version is used for the rear braking system with one driving axle.
Brake valve, ABS
Overview
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
1 Air inlet from air tank
2 Air outlet to trailer brake
3 Exhaust, via silencer
4 Electrical connector to EBS control unit
Schematic diagram
SD Silencer
IV Solenoid inlet valve for electronic brake pressure control
OV Solenoid outlet valve for electronic brake pressure control
The ABS brake valve is a solenoid control valve located near the front brakes on vehicles with single
front axles (FAA10). The ABS brake valve is electronically connected to the EBS control unit and
pneumatically from the electro pneumatic modulator to the brake cylinder.
When a wheel begins to lock during braking, the solenoid valves are rapidly opened and closed. Air
pressure is connected to the solenoid valves to increase their performance. The ABS brake valve is
only operational when the ABS function is activated by the EBS control unit.
The modulator consists of die cast housing, silencer, solenoid valves, pneumatic ports and electrical
connector.
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
Trailer control modulator
Overview
1 Air inlet from air tank
21 Air outlet to trailer brake
22 Control line to trailer brake
42 Control line footbrake modulator (primary circuit)
43 Control line parking brake valve
3 Exhaust, via silencer
4 Electrical connector to EBS control unit
Schematic diagram
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
RLV Relay valve
Fi Filter
SD Silencer
IV Solenoid inlet valve for electronic brake pressure control
OV Solenoid outlet valve for electronic brake pressure control
BV Solenoid valve for backup circuit
PS Pressure sensor
The purpose of the trailer control modulator is to control the trailer brake system.
There are two compressed air lines from the modulator to the trailer, one for supply air and one for
controls. The trailer control modulator communicates with the EBS control unit through analogue
signals.
The trailer control modulator basically consists of a pneumatic relay valve with two control chambers
for the service brakes, one control chamber for parking brake, three solenoid valves and a pressure
sensor. The trailer control modulator has one electrical connector and five pneumatic ports.
On the inlet side, the pneumatic connections comprises one supply line (port 1) and two control lines
(footbrake valve modulator to port 42 and parking brake valve to port 43).
On the outlet side, the pneumatic connections comprise the dual-line braking system to the trailer
(supply from port 21 and control from port 22).
The return air from the trailer brake circuit passes through the silencer.
The EBS control unit is connected to the trailer control modulator via the electrical connector and
controls three solenoid valves. During braking, the EBS unit closes the solenoid valve for back up
circuit and controls the solenoid inlet valve and outlet valve according to the signal from the pressure
sensor. Based on the operation of the inlet and outlet valves, a pneumatic control signal is sent to
the trailer brake circuit via port 22 of the trailer control modulator.
Related information
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.07.172 06/10/2023
For more information on the electrical architecture, refer to:
Wiring diagram
➠ Vehicle electronics overview, system description
Related functions
➠ Hand brake, function description
➠ Service braking, function description
Related systems
➠ Electronic braking system (EBS), system description
➠ Air supply, system description
➠ Service braking, system description
➠ Trailer brake, system description
Related components
➠ Footbrake valve, component description
➠ Parking brake control (HCU), component description
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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