SAS

4

15

-

-

4

-

-

10

-

-

16

-

-

5

-

-

11

-

-

17

-

-

6

SAS

2

12

-

-

18

-

-

DEVICE KEY

eTPCM

GSBC eTPCM-90

EPM0-3

GSBC EPM-90

FBM

GSBC FBM-40

SAS

SAS-80

Table 7 – Central ECU X5 Connector Pin Match

SD-27-5023V Rev 002 Bendix® GSBC® System and EBS-90™ (Global Scalable Brake Control System and Electronic Control Unit)

17

GSBC Central ECU

GSBC CENTRAL ECU
Central ECU

Central ECU Mud Cover

Central ECU Full Assembly

Figure 13 – Central ECU Parts and Full Assembly
This section is specifically aimed at providing information
about the Central ECU, as well as diagnosing,
troubleshooting, and addressing potential issues with the
Central ECU.
DESCRIPTION
The Bendix EBS-90 ECU (referred to as Central ECU or
GSBC Central ECU) is a 24V electronic control unit that is
the main controller for the GSBC system. This controller
provides for driver control over the braking characteristics
of air-braked heavy- and medium- duty trucks, tractors,
and buses.
The Central ECU is connected to and controls all other
components that comprise the GSBC system, in addition
to interfacing between the GSBC system and the rest of
the vehicle.
COMPONENT OVERVIEW
The Central ECU is comprised of two (2) main parts.
The first is the ECU and housing, which contains the
ECU circuitry, mounting points, electrical connectors, wire
guides, and housing. The second part is the Central ECU
Mud Cover, which is a plastic shell that snaps on to the
top of the Central ECU. The Mud Cover protects the wiring
harness and electrical connectors that are connected to
the Central ECU from dirt, debris, road spray, and impact.
The Central ECU is only available from the vehicle OEM,
as each ECU is programmed specifically to the VIN of each
vehicle. The Mud Cover is a generic part which is available
without special restrictions.

18

The Central ECU operates at a normal voltage of
approximately 24V-28V. The ECU will not operate below
18.5V or above 32V.
CONDITION

24V OPERATION
Min

Nom

Max

Operation Voltage Range

18.5V

28V

32V

Overvoltage

-

-

>36V

Undervoltage

<18.5V

-

-

Table 8 – Central ECU Operating Voltage
It includes the lateral acceleration sensor, which is used as
one (1) of the inputs to the Central ECU’s ESP functionality.
There are five (5) electrical connectors on the Central ECU,
numbered X1-X5. Four (4) of them are populated with pins:
X1, X2, X3, X5. The X4 connector does not have any pins
present by design.

If you modify a vehicle and do not update the Central
ECU, the GSBC system may fail to function as intended.
Serious vehicle braking and performance issues
could result, including unnecessary ESP system
interventions, exceeding regulated stopping distance,
and/or system faults leading to loss of electronic
functions. These types of failures can lead to a lossof-control of the vehicle, potential collisions, property
damage, serious injuries, and/or death.

SD-27-5023V Rev 002 Bendix® GSBC® System and EBS-90™ (Global Scalable Brake Control System and Electronic Control Unit)

GSBC Central ECU
GSBC CENTRAL ECU MAINTENANCE
The Central ECU itself is not designed to need periodic
maintenance. The Central ECU can detect both internal
(related to the ECU) and external (related to other GSBC
components, the vehicle, or possibly the electrical harness)
faults, and provide notification through warning indicator
lamps. For more information about GSBC warning indicator
lamps, refer to BW8207, GSBC System Operator’s Manual,
on B2Bendix.com.
Mechanical or Physical Damage
It is not possible to repair a physically damaged Central
ECU. If the Central ECU needs to be replaced, contact the
vehicle manufacturer for replacement information.
If the Central ECU Mud Cover is damaged or missing, the
replacement is available from an authorized Bendix retailer.
Refer to the Replacement section on page 22.

The Mud Cover must always be installed on the Central
ECU, and if the Mud Cover is damaged, it should be
replaced. Failure to use the Mud Cover on a Central
ECU can result in a wiring harness failure, damage
to the electrical connectors, and/or damage to the
Central ECU. Serious vehicle braking and performance
issues could result, including unnecessary ESP system
interventions, exceeding regulated stopping distance,
and/or system faults leading to loss of electronic
functions. These types of failures can lead to a lossof-control of the vehicle, potential collisions, property
damage, serious injuries, and/or death.

GSBC CENTRAL ECU WARRANTY INFORMATION

IMPORTANT
Review the Bendix Warranty Policy before performing
any intrusive maintenance procedures. A warranty
may be voided if intrusive maintenance is performed
during the warranty period. No two vehicles operate
under identical conditions; as a result, maintenance
intervals may vary. Experience is a valuable guide in
determining the best maintenance interval for air brake
system components. At a minimum, the Central ECU
should be visually inspected for damage and proper
mounting every 6 months or 1500 operating hours,
whichever comes first.

IMPORTANT
The Central ECU is designed not to require maintenance,
and there are no user-serviceable components located
inside the ECU housing. Disassembly of the device
will void the component warranty and Bendix will not
provide technical support or replacement components
for components internal to the ECU.

Electrical or Internal Damage
If a DTC triggers a warning indicator lamp on the vehicle,
the technician must first read the DTC using the appropriate
diagnostic tool. If the DTC indicates that the GSBC Central
ECU component must be replaced, refer to the Replacement
section on page 22 for more information.

SD-27-5023V Rev 002 Bendix® GSBC® System and EBS-90™ (Global Scalable Brake Control System and Electronic Control Unit)

19

GSBC Central ECU
ELECTRICAL INTERFACES
Electrical Connectors
For an electrical schematic of the entire system, refer to the GSBC System Schematics section of this document.
NOTE: All connectors described in this section are located on the GSBC Central ECU.

X5
X3
X2
X1
X4

(unused)

X1

X1 CONNECTOR ON CENTRAL ECU
PIN NO.

DESCRIPTION

PIN NO.

DESCRIPTION

1

Front Left Modulator Common/Ground

9

Not used

2

Front Left Modulator Exhaust/Outlet

10

Not used

3

Front Left Modulator Hold/Inlet

11

Trailer modulator - 2nd pressure sensor
signal

4

Front Right Modulator Common/Ground

12

Not used

5

Front Right Modulator Exhaust/Outlet

13

Not used

6

Front Right Modulator Hold/Inlet

14

Power Line Communication

7

GSBC System ground

15

GSBC System Power supply

8

GSBC System ground

16

GSBC System Power supply

Table 9 – X1 Connector Pin Descriptions

Figure 14 – Central ECU X1 Connector Pinout

X2

X2 CONNECTOR ON CENTRAL ECU
PIN NO.

DESCRIPTION

PIN NO.

DESCRIPTION

1

EPM2 voltage supply

10

EPM3 Brake CAN High

2

EPM2 ground

11

EPM3 Brake CAN Low

3

EPM3 voltage supply

12

EPM3 Brake CAN High

4

EPM3 ground

13

EPM3 Brake CAN Low

5

Not used

14

eTPCM pressure sensor signal

6

eTPCM valve supply

15

eTPCM pressure sensor supply

7

eTPCM valve backup

16

eTPCM pressure sensor GND

8

eTPCM valve input

17

Not used

9

eTPCM valve output

18

Not used

Table 10 – X2 Connector Pin Descriptions

Figure 15 – Central ECU X2 Connector Pinout
20

SD-27-5023V Rev 002 Bendix® GSBC® System and EBS-90™ (Global Scalable Brake Control System and Electronic Control Unit)

GSBC Central ECU
ELECTRICAL INTERFACES (CONT.)
Electrical Connectors (cont.)
For an electrical schematic of the entire system, refer to the GSBC System Schematics section of this document.
NOTE: All connectors described in this section are located on the GSBC Central ECU.

X5
X3
X2
X1
X4

(unused)

X3

X3 CONNECTOR ON CENTRAL ECU
PIN NO.

DESCRIPTION

PIN NO.

DESCRIPTION

1

EPM0 ground

10

EPM0 Brake CAN High

2

EPM0 supply

11

EPM0 Brake CAN Low

3

EPM1 supply

12

EPM1 Brake CAN High

4

EPM1 ground

13

EPM1 Brake CAN Low

5

Chassis subnet CAN_High

14

Backbone_1_CAN_H

6

Chassis subnet CAN_Low

15

Backbone_1_CAN_L

7

Not used

16

Not used

8

Brake pedal sensor GND

17

Brake pedal sensor signal 1

9

Brake pedal sensor Supply

18

Brake pedal sensor signal 2

Table 11 – X
3 Connector Pin Descriptions

Figure 16 – Central ECU X3 Connector Pinout

X5

X5 CONNECTOR ON CENTRAL ECU
PIN NO.

DESCRIPTION

PIN NO.

DESCRIPTION

1

Not used

10

Not used

2

Not used

11

Not used

3

Not used

12

Not used

4

Not used

13

Not used

5

Not used

14

Not used

6

SENS_SPL

15

Not used

7

SENS_GND

16