the ECU.

Bendix® WS-24™ Wheel Speed Sensors
FIGURE 9 - POWER LINE WITH PLC SIGNAL

The application of PLC technology for the heavy vehicle
industry in North America is known as “PLC4Trucks.”
The Bendix ® ESP ® EC‑80™ Controller supports PLC
communications in accordance with SAE J2497.
PLC SIGNAL
An oscilloscope can be used to measure or identify the
presence of a PLC signal on the power line. The PLC
signal is an amplitude and frequency-modulated signal.
Depending on the filtering and load on the power line,
the PLC signal amplitude can range from 5.0 mVp-p to
7.05 Vp-p.

Wheel speed data is provided to the Bendix ESP EC‑80
Controller from the Bendix® WS-24™ wheel speed sensor
(see Figure 2). Vehicles have an exciter ring (or “tone
ring”) as part of the wheel assembly. As the wheel
turns, the teeth of the exciter ring pass the wheel speed
sensor, generating an AC signal. The Bendix ESP EC‑80
Controller receives the AC signal, which varies in voltage
and frequency as the wheel speed changes.
Vehicle axle configurations determine the number of
Bendix WS‑24 wheel speed sensors that must be used.
A vehicle with a single rear axle requires four wheel speed
sensors. Vehicles with two rear axles can utilize six wheel
speed sensors for optimal performance.

5

Diagnostic Blink Code Switch

Stop Lamp Switch (SLS)

A momentary switch that grounds the ABS Indicator Lamp
output is used to place the ECU into the diagnostic blink code
mode and is typically located on the vehicle’s dash panel.

The Bendix ESP EC‑80 Controller monitors the vehicle
stop lamp status. Certain vehicle functions, such as
ATC and All-Wheel Drive (AWD), use the status of the
stop lamp to determine when the driver makes a brake
application. This can be provided to the ECU via J1939
communications, or hardware input.

Optional ABS Off-Road Switch and Indicator
Lamp Operation
Vehicle operators use an optional dash-mounted switch to
place the Bendix® ESP® EC‑80™ Controller into the ABS
off-road mode. See "Optional ABS Off-Road Mode" on
page 10 for further details. In some cases, ECUs may
also be put into the ABS off-road mode by one of the other
vehicle control modules, using a J1939 message to the
Bendix ESP EC‑80 Controller.
(If you need to know if a specific Bendix ESP EC‑80
Controller uses a J1939 message to operate the lamp,
contact the Bendix Tech Team. E-mail the Tech Team
at ABS@bendix.com (be sure to specify the ECU part
number), or call 1‑800‑AIR‑BRAKE (1-800-245-2725).

The ABS off-road mode should not be used on
normal, paved road surfaces because vehicle
stability and steerability may be adversely affected.
When the ECU is placed in the ABS off-road mode,
the ABS Indicator Lamp will flash constantly (at a
rate of once per 2.5 seconds) to notify the vehicle
operator that the off-road mode is active.

Optional ATC Mud/Snow (Off-Road) Switch and
Indicator Lamp Operation (also see page 8.)
The Bendix ESP system uses a dash-mounted switch for the
operator to place the ECU into the ATC Mud/Snow mode.

Optional Hill Start/Hill Start Assist Feature
Switch and Lamp Operation (see also page 8.)
ESP Controllers use a dash-mounted switch for the
operator to place the ECU into the hill start mode. This
feature interfaces between the transmission and the
braking system to help the driver prevent the vehicle from
rolling downhill when moving up a steep incline from a
stationary position.

With Hill Start Aid Feature option you lose the ABS
off-road function and the retarder relay output.
When the ECU is placed in the Hill Start Aid (HSA) feature
mode, the HSA Indicator Lamp will flash constantly (at a
rate of once per 2.5 seconds) to notify the vehicle operator
that the HSA mode is active. The ECU receives J1939
messages from the transmission to engage the HS/HSA
components. When engaged, the system applies 44 psi to
the rear brakes for three (3) seconds then releases. This
function is totally controlled by the automatic transmission.
6

Brake Demand Sensors
The brake demand sensors provide the Controller with an
indication of driver-applied brake pressure. One is installed
in the primary air brake circuit, and another is installed in
the secondary air brake circuit.

Load Sensor
The load sensor provides the Controller with an indication
of the vehicle load. It is typically installed in one of the
suspension air bags.

Bendix® SAS-70X™ Steering Angle Sensor
Bendix® brand Steering Angle Sensors (SAS) are used to
report the steering wheel position to the Controller, utilizing
a dedicated serial communications link that is shared with
the Yaw Rate Sensor. The Controller supplies the power
and ground inputs to the Bendix® SAS‑70X™ sensor.
The Bendix SAS-70X sensor is available with two different
styles of wire harness connectors. (See Figure 4.)

Bendix® YAS-60™ or YAS-70X™ Yaw Rate/Lateral
Acceleration Sensors
Bendix® brand yaw rate/lateral acceleration sensors are
used to provide the Controller an indication of vehicle
lateral acceleration and rotation around the vertical axis.
This information is provided to the Controller, utilizing a
dedicated serial communications link that is shared with
the Bendix® SAS-60™ sensor. The Controller supplies the
power and ground inputs to the yaw rate sensor.

BENDIX® ESP® EC‑80™ CONTROLLER
OUTPUTS
Bendix® M-40QR™ and M-40HF™ Pressure
Modulator Valves (PMVs)
The Bendix ESP EC‑80 Controller operates Bendix ®
M-40QR™ and M-40HF™ Pressure Modulator Valves
(PMVs) to modify the driver-applied air pressure to the
service brakes during ABS, ATC, RSP or YC activation
(see pages 9-13). The PMV is an electropneumatic
control valve and is the last valve that air passes through
on its way to the brake chamber. The modulator hold and
release solenoids are activated to "modulate" or "control"
the brake pressure during an antilock braking event. The
hold solenoid is normally open and the release solenoid is
normally closed, such that the PMV nominally allows air to
flow through. This design allows for air delivery to brake
chambers in the event of electrical trouble.

The Bendix ® ESP ® EC‑80™ Controller also utilizes an
additional Pressure Modulator Valve (PMV) for control
of the trailer service brakes during stability interventions.

Traction Control Valve (TCV)
Bendix ESP EC‑80 Controllers use two TCVs, one on the
steer axle and one on the drive axle. The TCV may be a
separate valve or integrated into the rear axle relay valve.
The Controller will activate the drive axle TCV during
differential braking ATC events.
During stability interventions, the Controller will activate
both the steer axle and drive axle TCVs as required.

Stop Lamp Output
The Controller provides an output to control a relay
that illuminates the vehicle stop lamps during stability
interventions. This information is also available using the
J1939 serial communications link.

ABS Indicator Lamp Control with Optional
Diagnostic Blink Code Switch
The Bendix ESP EC‑80 Controller has internal circuitry to
control the ABS Indicator Lamp on the dash panel.
The ABS Lamp Illuminates:
1. During power up (e.g. when the vehicle is started) for
approximately three (3) seconds and turns off after the
self‑test is completed, providing no Diagnostic Trouble
Codes (DTCs) are present on the ECU;
2. When full ABS operation is not available due to the
presence of a DTC on the ECU;
3. If the ECU is unplugged or has no power;
4. When the ECU is placed into the ABS off-road
mode (the lamp flashes steadily at a rate of once per
2.5 sec.); or
5. To display blink codes for diagnostic purposes after the
external diagnostic switch is activated.
The Bendix ESP EC‑80 Controller may communicate
with other vehicle control modules to operate the ABS
Indicator Lamp using serial communications. (If you
need to know if this Bendix ESP EC‑80 Controller uses
serial communications to operate the lamp; e-mail ABS@
bendix.com, (be sure to specify the ECU part number), or
call 1‑800‑AIR‑BRAKE/1-800-247-2725 and speak to the
Bendix Tech Team.)

Indicator Lamp Control Using Serial
Communications Links
As mentioned above, depending on the vehicle
manufacturer, the dash indicator lamps (ABS, ATC,
ESP, and trailer ABS) may be controlled using serial
communications links. In these cases, the Bendix ESP
EC‑80 Controller will send a serial communications
message over the J1939 link, indicating the required status
of the lamp(s). Another vehicle control module receives
the message and controls the indicator lamp(s).

Dynamometer Mode Indicator Lamp Operation
When the Bendix ESP EC‑80 Controller is put into the
Dynamometer mode for testing purposes, the ATC
Indicator Lamp will be illuminated.

Retarder Relay Disable Output
The retarder relay disable output may be used to control a
retarder disable relay. When configured to use this output,
the ECU will energize the retarder disable relay and inhibit
the use of the retarder as needed.
If the ECU is configured for the Hill Start/ Hill Start Assist
feature (HS/HSA), the retarder relay output pin is used to
control the Hill Start status lamp. As a result, the vehicle
loses the retarder relay function when it has the Hill Start
feature.

SAE J1939 Serial Communications
A Controller Area Network (CAN) data link (SAE J1939) is
provided for communication. This link is used for various
functions, such as:
• Diagnostic purposes.
• To disable retarding devices during ABS operation.
• To request that the torque converter disable lock-up
during ABS operation
• To share information such as wheel speed and ECU
status with other vehicle control modules.
Bendix ESP EC‑80 Controllers utilize the J1939 data link
for:
• ATC and drag torque control functions.
• Vehicle stability functions.

Trailer ABS Indicator Lamp Control
The Bendix ESP EC‑80 Controller will activate a trailer ABS
Indicator Lamp (located on the dash panel) that indicates
the status of the trailer ABS unit on one, or more trailers, or
dollies that are equipped with PLC functionality. Typically,
the Bendix ESP EC‑80 Controller directly controls the
trailer ABS Indicator Lamp based on the information it
receives from the trailer ABS, via PLC.
Alternatively, some vehicles require the Bendix ESP EC‑80
Controller to activate the trailer ABS Indicator Lamp by
communicating with other vehicle Controllers using serial
communications.
(If you need to know if this Bendix ESP EC‑80 Controller
uses a serial communications message to operate the
lamp, e-mail ABS@bendix.com (be sure to specify the ECU
part number), or call 1-800-AIR-BRAKE (1-800-245-2725)
and speak to the Bendix Tech Team.)

Interaxle Differential Lock Control
(AWD Transfer Case)
Bendix ESP EC‑80 Controllers can control the interaxle
differential lock (AWD transfer case). This is recommended
on AWD vehicles, but the ECU must be specially configured
to provide this feature. E-mail ABS@bendix.com for more
details.
7

INDICATOR LAMPS AND POWER-UP
SEQUENCE
NOTICE: The vehicle operator should Verify the proper
operation of all installed indicator lamps (ABS, ATC/ESP,
and trailer ABS) when applying ignition power and during
vehicle operation. See Figure 10.
Dash Lamp Behavior for the
Bendix® ESP® EC‑80™ Controller

ABS

TRLR

HSA

ATC

ABS
Lamp

Mode

Lamps that do not illuminate as expected when ignition
power is applied, or remain illuminated, indicate the need
for maintenance.

ATC/ESP Lamp

Trailer
ABS Lamp

HSA
Lamp

Comments

At Vehicle Startup

*
Ignition on - start up
[trailer with Power Line
Carrier (PLC)]

ON for
three (3)
seconds*

ON for 2.5
seconds*

ON for
three (3)
seconds*

** Some vehicle manufacturers may
3 seconds after ignition
[with no Diagnostic
Trouble Codes (DTCs)]

Lamp OFF*

Lamp OFF*

Normal

Special Mode Operation

ON for
three (3)
seconds**

If any of the described lamp behaviors
do not occur — or if the lamp remains
on during operation — have the vehicle
serviced by a qualified mechanic as
soon as possible to restore full system
functionality.

ABS
Lamp flashes
Off-Road
slowly (every 2.5
During an ATC
Mode
seconds)
Event

Lamp OFF

Flashes quickly

Lamp OFF**

illuminate the trailer ABS indicator lamp
at power‑up regardless of whether a
PLC signal is detected from the trailer or
not. Consult the vehicle manufacturer’s
documentation for more details.

Lamp
OFF*

• Uses dash switch
• Not for firm road surfaces
• Allows more wheel lock-up (less ABS intervention)
• Mode only applies under 25 mph (Over 25 mph, the system reverts to
full ABS - including ATC/ESP — and upon exiting off-road mode, the
ATC lamp extinguishes.)

-— OR, depending on vehicle options (a vehicle can have either ABS off-road or HSA) —
Vehicles with Hill Start Aid (HSA):
During HSA Mode
(“Hill Start” / “Hill Start Assist”)

Deep
Mud/
Snow/
Mode

During HSA Event

Lamp OFF

HSA Manually Disabled

Flashes
slowly

Normal

OFF

Flashes slowly
(every 2.5
seconds)

During an
ATC/ESP
Event

OFF

Flashes quickly

During an Automatic Traction Control (ATC) Event

Flashes quickly

During Dynamometer Mode

Lamp ON
(ATC
Disabled)

During an ESP Event

Flashes quickly

ABS System
Status Indicators
at Start-Up

Power
Application
0.5 1.5 2.0 2.5 3.0 (sec.)

• The HSA lamp is illuminated only at powerup, or if an HSA DTC is present

• Uses dash switch
• Increases allowable wheel slip during ATC interventions
• Not for firm road surfaces

• Reduces wheel slip during acceleration at low speeds
• Disables ATC monitoring functions
• When not in Dynamometer Mode, an illuminated lamp indicates an
ATC DTC is present
• System intervenes to reduce the risk of rollovers, loss-of-control, etc.

ATC/ESP System
Status Indicator
at Start-Up

ON

Powered Vehicle ABS
Indicator Lamp OFF
Trailer ABS ON
Indicator Lamp
(PLC Detected)** OFF
Trailer ABS ON
Indicator Lamp**
(PLC Not Detected) OFF

Power
Application

0.5 1.5 2.0 2.5 3.0 (sec.)

ATC/ESP
enabled

ON
OFF
ON

No ESP
or ATC

FIGURE 10 - BENDIX® ESP® EC‑80™ CONTROLLER INDICATOR LAMP BEHAVIOR
8

OFF

ABS Indicator Lamp Operation (Bulb Check)
The Bendix® ESP® EC‑80™ Controller will illuminate the
ABS Indicator Lamp for approximately three seconds when
ignition power is applied, after which the lamp will extinguish
if no Diagnostic Trouble Codes (DTCs) are detected.
The Controller will illuminate the ABS Indicator Lamp
whenever full ABS operation is not available due to a DTC.
In most cases, partial ABS is still available.

ATC/ESP Status/Indicator Lamp Operation
The Bendix ESP EC‑80 Controller will illuminate the ATC/
ESP lamp for approximately 2.5 seconds when ignition
power is applied, after which the lamp will extinguish if
no DTCs are detected. The Controller will continuously
illuminate the ATC/ESP Indicator Lamp whenever ESP or
ATC is disabled due to a DTC.
During an ESP or ATC intervention, the lamp will flash
rapidly (2.5 times per second). When the Controller is
placed in the ATC Mud/Snow (off-road) mode, the lamp
will flash slowly at a rate of once every 2.5 seconds.

Trailer ABS Indicator Lamp Operation
The Controller will control the Trailer ABS Indicator Lamp
when a PLC signal (SAE J2497) from a trailer ABS ECU
is detected.

Hill Start Assist (HSA) Indicator Lamp Operation
Vehicles with HSA enabled, will illuminate the HSA
Indicator Lamp when ignition power is applied. The lamp
will extinguish if there are no issues with the HSA system.

Pressure Modulator Valve (PMV) and Traction
Control Valve (TCV) Chuff Test
Right Steer

Right Drive

Right
Additional

Left Drive

Left
Additional

Driver

Left Steer

FIGURE 11 - VEHICLE ORIENTATION (TYPICAL)

After the performance of the configuration test, the Bendix
ESP EC‑80 Controller will perform a Bendix-patented PMV
and TCV Chuff Test. The Chuff Test is an electrical and
pneumatic PMV test that can assist maintenance personnel
in verifying proper PMV wiring and installation.
When ignition power is applied, each modulator solenoid
is briefly energized. If the air system is fully charged and
the service brake pedal is depressed during ignition, the
modulator creates a single, sharp audible “chuff” of air
pressure. The modulators are energized in a certain
pattern: right front; left front; right rear; then left rear.

This test is performed only when the vehicle is stationary
(if the vehicle moves, the Chuff Test will not be performed).
The Bendix ESP EC‑80 Controller will perform a PMV
Chuff Test on all installed modulators in the following order:
•

Steer Axle Right PMV;

•

Steer Axle Left PMV;

•

Drive Axle Right PMV;

•

Drive Axle Left PMV;

•

Additional Axle Right PMV;

•

Additional Axle Left PMV; then

•

Drive Axle TCV

The pattern will then repeat itself. See Figure 11.
Vehicles with a Bendix ESP EC‑80 Controller — following
the completion of the second round of PMV & TCV Chuff
Tests — the Controller (if configured to do so) will perform
a test to cross-check the trailer PMV operation with the
vehicle stop lamps. If the trailer PMV circuit is mis-wired
(including the steer axle TCV), the PMV will exhaust a large
amount of air, or none at all.
NOTICE: If there are any active DTCs, the stop lamp
cross-check portion of the Chuff Test will not be carried out
until all DTCs are fully diagnosed and the corresponding
repairs are successfully conducted. The ESP/ATC dash
indicator will also illuminate when there are active ABS,
ATC or ESP DTCs.
The ECU will not perform the PMV Chuff Test when wheel