SD-13-47680

Bendix® TABS‑8™ Advanced Single-Channel Trailer Antilock
Braking System (ABS) Module
Through-holes for Frame
(Chassis) Mounting

Electronic Control
Unit (ECU)
(Sealed)

ECU
Wheel Speed
Connector Sensor (WSS)
Cover
Connectors
(Removable) (S-D and S-C)

3/8-in. NPT Load Port
(Air Suspension)
3/8-in. NPT
Control Port with
Integral Filter

Electronic
Control Unit
(ECU) Part
To Remove Number Label
Cover, Slide
Lock Tab

3/4-in. NPT
Supply Port
with Integral
Filter
Integrated
Modulator
Relay Valve

7-Pin Connector

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

2-Pin
Sensor
Connectors
(S-F and
S-E) for
Auxiliary
Features

The Bendix® TABS-8™ Advanced Single-Channel ABS Module ports
contain parallel ribs as shown. These ribs identify the module as a
genuine Bendix® product. If the TABS-8 Advanced Module being
serviced does not contain these ribs, it is not a genuine Bendix product.

Figure 1 – Bendix ® TABS‑8™ Advanced Single-Channel ABS Module Plus View of Connector

1. INTRODUCTION

The TABS-8 Advanced Module features:

The Bendix® TABS‑8™ Advanced 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) and
the Bendix® Trailer Roll Stability Program (TRSP®).

•

A modular design with an integrated Electronic
Control Unit (ECU); pressure sensors; a lateral
acceleration sensor; and Modulator Relay Valve
(MRV) – eliminating external pigtail harnesses for
these components

Installed on semi-trailers, the TABS-8 Advanced 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.
The TRSP monitors the trailer’s motion and reduces the
risk of rollovers by automatically applying the brakes when
a risk of rollover is detected.

•

An operating voltage range of 8 - 32 volts

•

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 up to 1,008 bytes of
freely definable read/write text space available for
customer use

•

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

1

•

•

•

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

•

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

•

A wide range of diagnostic tools for flexible
troubleshooting such as blink codes; SAE J2497
(PLC); SAE J1939 (CAN) diagnostics; the Bendix®
Trailer Remote Diagnostic Unit (TRDU); and the
Bendix® Trailer Information Module (TIM)

A pressure-equalizing valve in the sealed Electronic
Control Unit (ECU) housing to give improved
protection from water, etc.

•

Serviceable nylon filters to help prevent foreign
material from entering the control port, load sensor
port, and supply port

•

Locking dust cover to provide electrical connector
and cable protection

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

3/8-in. NPT Load Port 42
for Air Suspension
(Plugged for ABS only configurations)

3/4" NPT Supply
Port 1

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

Tab distinguishes a
Bendix® TABS-8™
cover from a Bendix®
TABS-6™ cover

Four (4) 3/8-in. NPT
Delivery Ports 21
(to brake chambers)

Figure 2 – Ports Used

2

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.

Disconnect the electrical connectors from the Antilock
Braking System (ABS)/Bendix® Trailer Roll Stability
Program (TRSP®) controller before welding on the
trailer.

Dielectric grease should be applied to electrical
connectors to help protect against moisture intrusion.

Bendix ® -brand Electronic Control Units (ECUs)
are not designed to store data for purposes of
accident reconstruction, and Bendix® ACom® PRO™
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.

Section TABLE OF CONTENTS . . . . . . . . . . . PAGE
1.
2.
3.
4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
General Safety Guidelines . . . . . . . . . . . . . . . . . 3
Antilock Braking System (ABS) Operation . . . . . 4
Bendix® Trailer Roll Stability Program (TRSP®)
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
6. Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Pigtail Wiring Harnesses . . . . . . . . . . . . . . . . . . .7
8. ABS Indicator Lamp . . . . . . . . . . . . . . . . . . . . . . 8
9. Bendix® WS-24™ Wheel Speed Sensors (WSS) . 8
10. SAE J2497 (PLC) Diagnostic Link . . . . . . . . . . . 9
11. SAE J1939 (CAN) Diagnostic Link . . . . . . . . . . . 9
12. Auxiliary I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
13. Bendix® ABS Flex™ Program . . . . . . . . . . . . . . 10
14. Customer Scratch Pad . . . . . . . . . . . . . . . . . . . 10
15. Power-Up Sequence . . . . . . . . . . . . . . . . . . . . .10
16. Odometer Function . . . . . . . . . . . . . . . . . . . . . . 10
17. Non-Standard Tire Size . . . . . . . . . . . . . . . . . . 11
18. Diagnostic Trouble Code (DTC) Detection . . . . 11
19. Partial ABS Shutdown . . . . . . . . . . . . . . . . . . . . 11
20. Blink Code Diagnostics . . . . . . . . . . . . . . . . . 11-12
21. Auxiliary Features . . . . . . . . . . . . . . . . . . . . . . . 12
22. Diagnostic Trouble Codes (DTC) . . . . . . . . . 13-19
23. Troubleshooting Section . . . . . . . . . . . . . . . . 20-42

3

3. ANTILOCK BRAKING SYSTEM
(ABS) OPERATION
The Bendix TABS‑8 Advanced Module uses Wheel
Speed Sensors (WSS), a Modulator Relay Valve (MRV),
and an Electronic Control Unit (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 apply controlled
brake pressure at the wheel ends.
The TABS‑8 Advanced Module ECU is able to modulate
the brake pressure with greater speed and accuracy than
a driver.

Normal Braking
During normal braking, the TABS‑8 Advanced Module
functions as a standard relay valve. If the ECU does not
detect excessive wheel slip, it will not activate the Antilock
Braking System (ABS), and the vehicle will stop with normal
braking.

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 TABS-8 Advanced 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
TABS‑8 Advanced Module will illuminate the trailer ABS
indicator lamp and revert to a fail-safe mode where some, or
all, advanced ABS functions (including the Bendix® Trailer
Roll Stability Program - TRSP®) may not function. Even in
cases where the ABS system is completely disabled, the
standard pneumatic brake function of the vehicle will still
be available, but without the benefits of ABS. The TRSP
feature is also disabled with an active ABS system DTC.
If the indicator lamp is illuminated, always have the ABS
system serviced at the earliest opportunity.

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.

Axle control (select high) should not be used on fifthwheel 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.
When intervening on regular-traction surfaces, a
system configured for axle control performs similar to a
side-control, two-modulator system.

4

For all NPT fittings, use of a thread sealant is
required. For NPTF fittings, the use of a thread
sealant is recommended. This can be a pre-applied
or a hand-applied sealant product (with PTFE).
When using a hand-applied sealant, use caution
so as not to over-apply. Always follow the fitting
manufacturer’s pre-applied or hand-applied thread
sealant recommendations. Use of PTFE tape is not
approved and will void the Bendix ABS/TRSP valve
warranty.

4. BENDIX® TRAILER ROLL STABILITY
PROGRAM (TRSP®) OPERATION

During a Bendix ® Trailer Roll Stability Program
(TRSP®) system intervention, the vehicle automatically
decelerates. The Bendix® TABS‑8™ Advanced Module
can slow the vehicle with or without the driver applying
the brake pedal, and even when the driver applies the
throttle.

The TRSP system reduces the risk of rollovers during
driving by automatic application of the service brakes when
the system detects potential rollover conditions. This is
accomplished with monitoring sensors both at the trailer
wheel ends and within the TABS-8 Advanced Module. The
TRSP system reacts by applying the trailer service brakes
and slowing the vehicle combination.
The Bendix TRSP system uses the following sensors:
•

Lateral Acceleration: A lateral accelerometer is
located within the TABS‑8 Advanced Module. This
sensor detects the lateral motion (or “roll”) of the
vehicle as it moves. The TABS-8 Advanced Module
may be mounted either in line with – or at right angles
to – the main trailer chassis to function correctly.
Refer to the Troubleshooting section for full details
on acceptable installation locations. NOTE: Do
not attempt to change the location of the TABS-8
Advanced Module without contacting Bendix for
engineering approval.

•

Vehicle Speed: The TRSP system obtains
information about the vehicle speed and rate of
acceleration/deceleration from the Wheel Speed
Sensors (WSS).

•

Axle/Bogie Load: The trailer’s axle load information
is obtained by the use of an integrated pressure
sensor port (P42) of the TABS‑8 Advanced Module,
where a direct reading of the suspension air spring
pressure is taken. Trailer axle load information is
configured during the installation test based off of
information provided by the trailer/axle manufacturer.

IMPORTANT
If the TABS-8 Advanced Module faults for any reason,
the brakes will not be applied.

Even with TRSP system-equipped vehicles, the driver
remains responsible for ensuring vehicle stability
during operation. The TRSP system only functions
within the limits of physics. The system can help
mitigate potential vehicle stability incidents, but
cannot prevent them in all cases. Other factors – such
as driving too fast for the road, traffic or weather
conditions, over-steering, an excessively high vehicle
Center of Gravity (CG), poor road conditions, or
insufficient vehicle maintenance – can cause vehicle
instability that is beyond the capability of any stability
system to mitigate.

TRSP Intervention with Driver Actions
The TRSP system should only be used on specific
vehicle platforms that have been validated and
approved by Bendix engineering.

The TRSP system is approved for use on A-Double and
B-Train combinations. Use on A-Triple combinations
must be approved by engineering.

It is possible the driver will also apply the brakes before
or during a TRSP intervention by the TABS‑8 Advanced
Module. In all cases, the Electronic Control Unit (ECU)
monitors the driver’s brake application and compares that
to the amount of braking the TRSP program has calculated
needs to be applied. The pressure delivered to the brakes
will always be the higher of the two (2) pressures.

5

5. COMPONENTS

External Components:

Installation of the Bendix TABS‑8 Advanced Module use
the following components:
®

™

•

Internal Components:
•

•

•

•

•

6

Electronic Control Unit (ECU): The ECU monitors
the Wheel Speed Sensor (WSS) signals, lateral
accelerometer sensor signal, and various pressure
sensors (listed below) to determine when the
Antilock Braking System (ABS) and/or the Bendix®
Trailer Roll Stability Program (TRSP® ) 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.
Diagnostic Trouble Codes (DTCs) are stored in the
ECU and can be reviewed to diagnose the TABS‑8
Advanced Module system.
Lateral Accelerometer Sensor: The lateral
accelerometer sensor recognizes the lateral
movement of the trailer and sends an electrical
signal directly proportional to the trailer’s lateral
acceleration to the ECU.

Use of cable ties/tie wraps to attach Wheel Speed
Sensor (WSS) leads to rubber hoses/jounce lines is not
approved. The hose may expand during braking due to
air pressure and the cable tie may not, so the conductor
material/insulation of the speed sensor extensions
may be damaged. Bendix instead recommends only
open-ended clips be used to hold sensor leads to
jounce lines.
Sensor
Clamping
Sleeve

Internal Load Sensor: For air suspension systems,
the Load Sensor Port (P42) must be plumbed to a
fixed-axle air ride bellows. NOTE: The sensor must
not be plumbed to a lift axle bellows since they are
not charged when the axle is not being used. The
function of this sensor is to monitor the pressure
and send an electrical signal directly proportional to
the trailer’s axle load to the ECU.

Acceptable
Logo-stamped
Sleeves
90° Speed
Sensors

Brake Demand Pressure Sensor: This internal
sensor (P4) monitors the trailer service brake
pressure being applied by the driver and sends an
electrical signal directly proportional to the driver’s
brake demand to the ECU.
Brake Delivery Pressure Sensor: This internal
sensor (P21) monitors the trailer service brake
pressure that is being delivered to the wheel ends
through, or by, the TABS‑8 Advanced Module
system and sends an electrical signal directly
proportional to the delivered trailer service brake
pressure to the ECU.

•

Modulator Relay Valve (MRV): An MRV is
integrated into the TABS-8 Advanced Module and
is controlled electrically by the ECU to decrease,
hold, or allow the fully applied brake pressure into