SD-20-47682
Bendix® iTABS™ X Standard Single-Channel (SC) Trailer
Antilock Braking System (ABS) Module
4-Pin Connectors for WSS
(SL, SR) and Optional
Tristate Inputs (SAL, SAR)

Electronic
Control Unit
(ECU) (Sealed)

ECU Connector Cover
(Removable)

7-Pin Connector

ECU Part
Number Label

3/4-in. NPTF
Supply Port
with Integral
Filter

Integrated
Modulator
Relay Valve

3/8-in. NPTF
Control Port
with Integral
Filter

The iTABS module ports contain parallel ribs as shown.
These ribs identify the module as a genuine Bendix®
product. If the iTABS module being serviced does not
contain these ribs, it is not a genuine Bendix product.

Four (4) 3/8-in. NPTF
Delivery Ports
(to Brake Chambers)

Figure 1 – Bendix ® iTABS™ X Standard SC ABS Module

1. INTRODUCTION
The Bendix® iTABS™ X Standard Single-Channel (SC) Module
(hereafter referred to as the iTABS module) is an integrated
single-channel (2S/1M) trailer service brake module controller
for air-braked, heavy-duty semi-trailers that features the
Bendix® Antilock Braking System (ABS).
Installed on semi-trailers, the iTABS module acts as a relay
valve during normal braking, but during ABS events, it will
intervene to help maintain vehicle stability and minimize
stopping distance by preventing wheel lock-up.

1

Bendix®-brand Electronic Control Units (ECUs) are
not designed to store data for purposes of accident
reconstruction, and Bendix® ACom® Diagnostic Software
is not intended to retrieve data for purposes of accident
reconstruction. Bendix makes no representations as to
the accuracy of data or video retrieved and interpreted
from ECUs for purposes of accident reconstruction.
Bendix does not offer accident reconstruction services
or interpretation of stored data. Bendix ECUs are not
protected from fire, loss of power, impact damage,
or other conditions that may be sustained in a crash
situation and may cause data to be unavailable or
irretrievable.

iTABS MODULE FEATURES
•

A modular design with an integrated Electronic
Control Unit (ECU) and Modulator Relay Valve (MRV)
– eliminating external pigtail harnesses for these
components

•

An operating voltage range of 9.0-16.0 VDC

•

Optional mounting to the service reservoir or to the
chassis without additional brackets

•

An electronic odometer with trip counters and service
interval options

•

A scratch‑pad feature with freely definable read/write
text space available for customer use

•

An extended data‑logging feature, including a
resettable drive recorder

•

A variety of electrical inputs and a single output
(I/Os) allow the customer to program auxiliary functions
such as Integrated Speed Switch (ISS) and Auxiliary
Design Language (ADL) for customized auxiliary
functions

•

A wide range of diagnostic tools for flexible
troubleshooting such as blink codes and SAE J1939
(CAN) diagnostics

•

Support for SAE J2497 Power Line Carrier (PLC)
communication to the towing vehicle

•

Support for SAE J1939 (CAN) communication for
diagnostics and external devices

•

A pressure‑equalizing valve in the sealed ECU housing
to give improved protection from water, etc.

•

Serviceable nylon filters to help prevent foreign
material from entering the control port and supply ports

•

ECU PART NUMBER LABEL
See Figure 2. The external part number label is located next
to the control port (P4) of the iTABS module. If this label is
not readable for any reason, the part number can be read
from the ECU using ACom Diagnostic Software.
SOFTWARE REVISION LEVEL
The number of the initial software loaded on the ECU is also
indicated. The current software revision number can be read
using ACom Diagnostic Software.
DOCUMENT REVISION LEVEL
For additional information on Bendix products and to ensure
you have the latest version of the Service Data Sheet, go to
B2Bendix.com.

Sensor Connector
Designation

QR Code to
B2Bendix.com
Product Information

Part Number
Voltage Specification

Locking dust cover to provide electrical connector and
cable protection

Figure 2 – Label Information

2

TABLE OF CONTENTS
1. Introduction ................................................................ 1
2. General Safety Guidelines ......................................... 3
3. Antilock Braking System (ABS) Operation.................. 4
4. Components................................................................ 5
5. Mounting Configurations............................................. 6
6. Wiring Harnesses........................................................ 6
7. SAE J2497 (PLC) Diagnostic Link.............................. 8
8. SAE J1939 (CAN) Diagnostic Link.............................. 8
9. Auxiliary I/O and Functions Pinout.............................. 9
10. Customer Scratch Pad................................................ 8
11. Power-up Sequence................................................... 9
12. Odometer Function..................................................... 9
13. Non-standard Tire Size............................................. 10
14. Diagnostic Trouble Code (DTC) Detection................ 10
15. Partial ABS Shutdown............................................... 10
16. Blink Code Diagnostics..............................................11
17. Auxiliary Features .................................................... 12
18. Diagnostic Trouble Codes (DTCs) ........................... 12
19. Troubleshooting........................................................ 13
20. Repair....................................................................... 14
Appendix 1................................................................ 19

To search DTCs and receive additional
troubleshooting support, refer to:
B2Bendix.com > Services & Support >
Diagnostic Trouble Code Search

3

2. GENERAL SAFETY GUIDELINES
GENERAL SAFETY GUIDELINES

WARNING! PLEASE READ AND
FOLLOW THESE INSTRUCTIONS
TO AVOID PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
guidelines should be observed AT ALL TIMES:
▲Park the vehicle on a level surface, apply the parking
brakes and always block the wheels. Always wear personal
protection equipment.
▲Stop the engine and remove the ignition key when working
under or around the vehicle. When working in the engine
compartment, the engine should be shut off and the ignition
key should be removed. Where circumstances require that
the engine be in operation, EXTREME CAUTION should be
used to prevent personal injury resulting from contact with
moving, rotating, leaking, heated or electrically-charged
components.
▲Do not attempt to install, remove, disassemble or
assemble a component until you have read, and thoroughly
understand, the recommended procedures. Use only the
proper tools and observe all precautions pertaining to use
of those tools.
▲If the work is being performed on the vehicle’s air brake
system, or any auxiliary pressurized air systems, make
certain to drain the air pressure from all reservoirs before
beginning ANY work on the vehicle. If the vehicle is
equipped with a Bendix® AD-IS® air dryer system, a Bendix®
DRM™ dryer reservoir module, a Bendix ® AD-9si ®, AD-HF®,
or AD-HFi ® air dryer, be sure to drain the purge reservoir.
▲Following the vehicle manufacturer’s recommended
procedures, deactivate the electrical system in a manner
that safely removes all electrical power from the vehicle.
▲Never exceed manufacturer’s recommended pressures.
▲Never connect or disconnect a hose or line containing
pressure; it may whip and/or cause hazardous airborne
dust and dirt particles. Wear eye protection. Slowly open
connections with care, and verify that no pressure is
present. Never remove a component or plug unless you are
certain all system pressure has been depleted.
▲Use only genuine Bendix ® brand replacement parts,
components and kits. Replacement hardware, tubing, hose,
fittings, wiring, etc. must be of equivalent size, type and
strength as original equipment and be designed specifically
for such applications and systems.
▲Components with stripped threads or damaged parts should
be replaced rather than repaired. Do not attempt repairs
requiring machining or welding unless specifically stated
and approved by the vehicle and component manufacturer.
▲Prior to returning the vehicle to service, make certain all
components and systems are restored to their proper
operating condition.
▲For vehicles with Automatic Traction Control (ATC), the ATC
function must be disabled (ATC indicator lamp should be
ON) prior to performing any vehicle maintenance where
one or more wheels on a drive axle are lifted off the ground
and moving.
▲The power MUST be temporarily disconnected from the
radar sensor whenever any tests USING A DYNAMOMETER
are conducted on a vehicle equipped with a Bendix ®
Wingman ® system.
▲You should consult the vehicle manufacturer's operating
and service manuals, and any related literature, in
conjunction with the Guidelines above.

3. ABS OPERATION
The iTABS module uses Wheel Speed Sensors (WSS), an
MRV, and an ECU to optimize the contact between the tires
and the road surface during a braking event where excessive
wheel slip – or wheel lock‑up – is detected.
When a situation is detected where the system needs
to intervene, the ECU will activate the MRV to modulate
controlled brake pressure at the wheel ends.
The iTABS ECU is able to modulate the brake pressure with
greater speed and accuracy than a driver.
NORMAL BRAKING
During normal braking, the iTABS module functions as a
standard relay valve. If the ECU does not detect excessive
wheel slip, it will not activate the ABS, and the vehicle will
stop with normal braking.
AXLE CONTROL
Axle control uses the MRV to control the wheels at both ends
of a given axle (or multiple axles in cases where the MRV is
controlling several axles).
In the case of braking surfaces with poor overall traction (i.e.
roads that are worn, slippery, or are made of loose gravel) –
or braking surfaces with areas of poor traction (i.e., asphalt
roads with patches of ice) – axle-control ABS interventions
will maintain the wheel that is not slipping at just under the
speed that will lock the wheel. The system permits the other
wheel (that is experiencing slippage) temporary periods of
wheel-lock during the intervention.

4

Do not use axle control (select high) on fifth-wheel dollies
or steerable axles. In these cases, it could cause a yaw
moment during braking that results in unwanted steering
of the axle. Use a dolly control (select low) configuration.
STEERABLE AXLES
For applications that have both fixed and steerable axles
– such as drawbar trailers (full-pull trailers) – a 4S/2M axle
configuration should be used. These configurations have the
ability to minimize yaw on steerable axles.
ABS FAIL-SAFE
The iTABS module is designed to react in a fail‑safe manner
in the event of a system Diagnostic Trouble Code (DTC). For
example, if the ECU detects that a sensor is not responding,
an ABS system DTC will be set. The iTABS module will
illuminate the trailer ABS indicator lamp and revert to a
fail‑safe mode where some – or all – advanced ABS functions
may not function. Even in cases where the ABS is completely
disabled, the standard pneumatic brake function of the trailer
will still be available, but without the benefits of ABS. If the
indicator lamp is illuminated, always have the ABS system
serviced at the earliest opportunity.

4. COMPONENTS

Sensor
Clamping
Sleeve

Installation of the iTABS module uses the following
components:
INTERNAL COMPONENTS
•

•

•

Acceptable
logo-stamped
sleeves

Electronic Control Unit (ECU): The ECU monitors
the WSS signals to determine when ABS intervention
is required. When needed, the ECU actuates the
internal pressure modulator valve to optimize the
brake pressure. The ECU monitors the system to
detect and warn the driver of any malfunctions.
DTCs are stored in the ECU and can be reviewed to
diagnose the iTABS module.
Modulator Relay Valve (MRV): An MRV is integrated
into the iTABS module and is controlled electrically by
the ECU to decrease, hold, or allow the fully applied
brake pressure into the brake chamber to control the
braking torque at the wheels.
MRV Crack Pressure: The iTABS MRVs are supplied
with a nominal crack pressure of 4.5 ± 0.5 psi.

90° Speed
Sensors

Straight Speed
Sensors

Figure 3 – Bendix ® WS-24™ Wheel Speed Sensor
•

Trailer-Mounted ABS Indicator Lamp: See Figure
4. The iTABS module controls an ABS indicator lamp
to show the trailer ABS status. With power supplied
by the towing vehicle – if there is an active DTC, or
during the bulb test at startup – the module illuminates
the ABS indicator lamp by providing a 12.0 VDC
signal (the other side of the lamp is grounded). The
ABS indicator lamp output uses Pin 4 of the 7-pin
connector on the module.

•

Dash-Mounted ABS Indicator Lamp (PLC
Controlled): The iTABS module uses SAE J2497
standards to support PLC communication. The status
of the trailer ABS is transmitted over the ignition
power wire (the blue wire of the J560 connector) – Pin
2 of the 7-pin module connector. If there is an active
DTC, during the bulb check at startup, the iTABS
module will transmit a signal over the power line to
the towing vehicle’s ECU, thus illuminating the trailer
ABS indicator lamp mounted on the dash.

EXTERNAL COMPONENTS
•

WSS: See Figure 3. Located at select hubs, WSS
detect the rotation of individual wheels and send
an electrical signal to the ECU proportional to the
rotational velocity. The WSS connectors, SR and SL,
are used for detecting wheel speeds. Regardless of
the mounting methodology of the module, the SR
WSS is always curb side, and the SL WSS is always
road side.

NOTE: Do not use
previous WSS
clamping sleeves
that have “BW” in a
diamond

Vehicles have an exciter ring (often referred to as
“tone ring”) as part of the wheel assembly. (Hereafter,
the exciter ring will be referred to as a tone ring
throughout this document.) The default setting expects
a 100-tooth tone ring to be used. Refer to Section 20
for more information. As the wheel turns, the teeth of
the tone ring pass the WSS, generating an Alternating
Current (AC) signal which is delivered to the iTABS
ECU. The signal varies in voltage and frequency as the
wheel speed changes. See Figure 8 for an electrical
schematic showing the WSS connector pin locations.
Refer to SD-13-4860, Bendix® WS-24™ Antilock WSS,
on B2Bendix.com for complete WSS information.

Figure 4 – Trailer-Mounted ABS Indicator Lamp
•

5

5-pin Power Harness: See Figure 5. A power
harness is required. Variations that include auxiliary
sub-harnesses are available as needed.

(K272484)
2-pin AUX I/O 1
TTMA RP 7‑99
5-pin Packard®
Weather Pack
Connector

7-Pin
ECU Main
Connector
4-pin J1939 CAN
and Power Output

15

16

14

13

12

I I

10

9

8

7

6

5

3

4

PART NO.

2
REVISION HISTORY

ZONE REV

L

A- I

DESCRIPTION

000

ENGINEER

DATE

CHANGE NO.

L

WHEEL SPEED SENSOR (WSS) HDSCS HARNESS
K

K

VARIOUS LENGTHS AND PART NUMBERS AVAILABLE

J

J

WHEEL SPEED SENSOR (WSS) EXTENSION HARNESS
2-pin Male DIN
Connector

2-pin
Female DIN
Connector

H

H

VARIOUS LENGTHS AND PART NUMBERS AVAILABLE
G

Figure 5 – Examples of Wiring Harnesses
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