normally. No service to the ABS
unit is needed.

33

SECTION C: TROUBLESHOOTING THE TRAILER-MOUNTED
ABS INDICATOR LAMP CIRCUITRY
Is the tractor ignition or battery
box (if not using tractor as power source)
switched ON?

Switch the ignition ON and re-check if the trailer
ABS indicator lamp does a power-up check. Go
to Troubleshooting Section A.

NO

YES
Is SAE J560
cable (green, spiral)
connected from the tractor/battery box to the
trailer?

Connect an SAE J560 cable. Verify that ABS
warning lamp turns ON and OFF during ignition
power-up.

NO

YES
Check the
tractor for constant
power (blue wire). Does the trailer
Electronic Control Unit (ECU) perform an ABS
indicator lamp power-on test when the brake
is applied while the trailer is
stationary?
YES

NO

Troubleshoot the main trailer power harness for
mis-wiring, open circuits, and/or short circuits.

Add constant power (blue wire) to the center pin of the SAE J560 connector..

Looking into the TABS‑6 ADV MC Module 7-pin connector pigtail harness.
Pin 4 is the ground pin. Pin 5 is the ABS indicator lamp pin.
ACTION: If the trailer-mounted ABS indicator lamp did
not illuminate during the power-up sequence...

Troubleshoot the power supply to the ABS module. Go to
Section D. Continue if the power and ground wiring are OK.

ACTION: If the trailer-mounted ABS indicator lamp
remains ON after the standard power-up time interval of
approximately 2.5 seconds...
Determine if a module Diagnostic Trouble Code (DTC) exists
using any of the following methods:
• Blink code diagnostics, Section 19
• PC diagnostics, Section 21

Turn the power to the module OFF. Inspect the condition of
the ABS indicator lamp, connector, and ground. Using a volt/
ohm meter, verify continuity from the trailer chassis ground pin
(pin 4) to the ground pin of the indicator lamp.
If repairs are made, rerun the power-up sequence. Go to
Section A.
Continue if the indicator lamp and ground wire check out
OK.

With power to the ABS module OFF, disconnect the 7-pin
ECU connector.
Verify continuity from the ABS indicator lamp pin (pin 5) of
the ECU connector to the ABS indicator lamp connector.
If repairs are made, rerun the power-up sequence. Go to
Section A. If the condition persists, contact the Bendix Tech
Team.

34

• Bendix® Trailer Remote Diagnostic Unit (TRDU™) and
magnet, Section 21
• Bendix® Trailer Information Module, Section 21
If DTC(s) exist, and repairs are made, rerun the power-up
sequence. Go to Section A. If no DTCs are found, the ABS
module appears to be functioning normally, but the ABS lamp
remains on, continue to the next step.

With power to the ABS module OFF, disconnect the 7-pin
ECU connector.
Apply power to the trailer. If the ABS lamp illuminates,
there is a voltage short on the lamp circuit. Troubleshoot,
repair, and retest. Use a volt meter to check if there is a
short to the voltage on the warning lamp circuit between the
ABS indicator lamp pin (pin 5) and the lamp. If repairs are
made, rerun the power-up sequence. Go to Section A. If the
condition persists, replace the ABS module.

SECTION D: TROUBLESHOOTING THE POWER SUPPLY

Turn power to the module OFF.
Disconnect the 7-pin Electrical Control
Unit (ECU) connector.

Check for high resistance (corrosion,
wire/connector damage, or improper
termination) of the power lines, resulting
in a high voltage drop across the lines.
Measure the voltage under load by
placing a load, such as a type 1157
brake light bulb, between the ignition
power pin and the ground pin of the
ECU connector, while the lamp is in
place.
With ignition power to the trailer,
measure the voltage between the
ignition power (pin 1) and ground pin
(pin 4) of the ECU connector.
Repeat the voltage measurement
with brake lamp power to the trailer,
between the brake lamp power (pin 2)
and the ground pin (pin 4) of the ECU
connector.
Verify that the voltage drop
measurements are no less than 1.0
VDC from the vehicle voltage at both
the ignition and brake power inputs.

YES

With ignition
power to the
trailer (engine running),
measure the voltage between
the ignition power pin (pin 1) and the
ground pin
(pin 4) of the ECU connector.
Repeat the voltage measurement between the brake
lamp power pin (pin 2) and the ground pin (pin 4) of the ECU
connector, while the service brake is being applied (the
brake lamp power should be supplied to the ECU).
Can you verify that measurements found
are equal to the vehicle voltage
(within 1 VDC) at both the
ignition and brake power
inputs?

NO
Look for corroded or damaged wires or
connectors. Check the power supply.
If repairs are made, rerun the power-up
sequence. Go to Section A.

With a volt/ohm meter, check the power
and ground wiring. Look for corroded or
damaged wires or connectors.

Measure the loaded
voltage across a type
1157 brake light bulb.

If repairs are made, rerun the power-up
sequence. Go to Section A.
If proper loaded and unloaded voltage
is measured at the ECU connector, and
no corrosion or damage is found on the
wiring, connectors or ECU, contact the
Bendix Tech Team.

Looking into the TABS-6 ADV
MC Module 7-pin Connector
Pigtail Harness Measure:
Ignition Power (pin 1) to
Ground (pin 4), and Brake
Lamp Power (pin 2) to Ground
(pin 4).

35

SECTION E: TROUBLESHOOTING THE WS-24 WSS

Turn the power to the module OFF and disconnect the wheel speed sensor connector. NOTE: For
some troubleshooting steps, both static and dynamic WSS Diagnostic Trouble Codes (DTCs) may
be present:
Wheel Speed Sensor
(different lengths available)
For additional troubleshooting steps, see Service Data Sheet SD-13-4860,
Bendix ® WS-24™ Antilock Wheel Speed Sensor.

NO

E1
Are there Static WSS
DTCs present?

YES

If Static WSS DTCs are present:
Using a volt/ohm meter to measure the connector pins of the sensor with a DTC, verify
950-1950 Ohms across the sensor connector pins.
Verify/inspect the following:
• No continuity from the sensor connector pins to ground
• Vbat is not measured at either sensor connector pins
• Verify there is no continuity between the sensor leads and other sensors
• Sensor/Electronic Control Unit (ECU) wiring and connectors are not damaged or
corroded
• Proper sensor wire routing and clamping
Make repairs as needed (replace wiring and/or ABS components)
Reset active DTCs by using any of the following methods:
• Blink code diagnostics, Section 19
• PC diagnostics, Section 21
• Bendix® Trailer Remote Diagnostic Unit (TRDU™) and magnet, Section 21
• Bendix® Trailer Information Module, Section 21
Then, check for dynamic WSS DTCs, See E3.
Then, rerun the power-up sequence. Go to Section A.

YES

E2
Are there dynamic
WSS DTCs
present?

Go to (E3)
36

NO
End

SECTION E: TROUBLESHOOTING THE WS-24 WSS (CONTINUED)

E3: Dynamic WSS Diagnostic Trouble Codes (DTCs) are present
NOTE: If dynamic WSS DTCs are related to a lift axle problem, they will typically
occur in pairs (“SE” and “SF”) or (“SC” and “SD”).

E4
Is the trailer
equipped with one (1) or
more lift axle(s)?

NO
Continue to E7: Sensor and wheel inspection.

YES
E5
Are there WSS installed
on the lift axle?

NO

YES
E6
Are sensors “SC”
and “SD” installed on the lift
axle?

NO

YES

Go to E7: Sensor and Wheel Inspection.

Sensors “SE” and “SF” are on the lift axle, as needed. Use the Bendix®
ACom® Diagnostic Software to check if the trailer is configured for a
lift axle. If the vehicle is not yet configured for a lift axle,use the ACom
Diagnostic Software to configure the trailer for a lift axle and configure
an auxiliary input/output (I/O) for lift axle sensing using the steps in
this document. When configuring a trailer for an automatic lift axle, the
system will either require a pressure switch be placed in one of the lift
air bags (as near as possible to – or actually in – the air bag), or an
automatic lift axle solenoid will need to be installed and configured.

The vehicle setup needs to be rearranged so that sensors
“SE” and “SF” are on the lift axle, and “SC” and “SD” are
on the stationary axle. Using the schematics, change
the vehicle to ensure all of the sensors are in the correct
locations for a lift axle, then rerun the power-up sequence.
E7: Sensor and Wheel Inspection

Rotate the affected wheel and verify a minimum of 0.25 VAC
sensor output is seen across the WSS pins while rotating the
wheel at least 0.5 rps. This voltage output will vary based on how
fast the wheel is being rotated.
NOTE: A properly positioned sensor can output more than 2.0
VAC at 1 rps.
Verify/inspect the following:
•
•
•
•
•
•
•
•

WSS properly contact the tone ring
The condition and retention force of the sensor sleeve
Proper sensor lead condition, routing, and clamping sleeve
Condition of the tone ring mounting and teeth
Proper number of tone ring teeth per sensed wheel
Proper adjustment of wheel bearings
Condition of the foundation brakes
Check for corroded/damaged wiring or connectors between
the ECU and the WSS
Then, rerun the power-up sequence. Go to Section E8.

E8: Repairs

Make repairs as needed (replace wiring and/or ABS
components).
Reset active DTCs by using any of the following
methods:
• Blink code diagnostics, Section 19
• PC diagnostics, Section 21
• Bendix® Trailer Remote Diagnostic Unit (TRDU™)
and magnet, Section 21
• Bendix® Trailer Information Module, Section 21
NOTE: If you do not reset manually, these will typically
reset automatically after a power cycle and the vehicle
has been driven for a period of time.
Then, rerun the power-up sequence. Go to Section A.

37

SECTION F: TROUBLESHOOTING THE
LOAD SENSOR (OUT-OF-RANGE CONDITION)
(NOTE: The indicator lamp for this condition is illuminated only after the vehicle moves.)
Turn power to the module OFF.

For spring suspension system trailers:
Verify/inspect the following:
1.

2.

3.

Inspect the load sensor linkage.
•

Check that the linkage is attached to the axle clamp.

•

Inspect for damage to the linkage components, loose
connectors, and improper installation.

•

heck that the load sensor lever rod is in a horizontal
C
position with the trailer empty. Verify that it is a
Bendix® sensor.

•

erify that the sensor linkage has not flipped over so
V
that it faces the opposite direction.

Switch the power to the module ON. Using the Bendix®
ACom® Diagnostic Software, open the Bendix® Trailer
Roll Stability Program (TRSP®) Sensor screen and select
Start. Find the load (in lbs.) that the sensor is registering,
and verify the actual trailer load is consistent with the
value found. See the NOTE below.
Where the value does not appear to be correct, perform
the load sensor resistance check:
•

nplug the 12-pin connector, or the 2.4 (X4
U
connector), from the module. Refer to Table 3.
• With the load sensor lever in the horizontal position,
verify that approximately 2.5K Ohms is measured
between the sensor supply pin and the sensor
input pin, and between sensor input pin and sensor
ground. Refer to Table 3.
• Using the ACom Diagnostic Software, open the
configuration screen. Select the Load and Sensor
Configuration tab, and then view the Load Sensing
panel. Verify that the current Sensing Type is shown
as External. If not, change the selection to External.
Perform the external spring deflection sensor
calibration. Refer to Instruction Sheet S-1588, Spring
Deflection Sensor.
• Note the values shown on the screen for the current
load and sensor voltage. Verify that the values
shown on the screen for the empty and laden weight
and voltage are correct. Where the value does not
appear to be correct, enter the correct value(s) on the
configuration screen.
NOTE: Use a scale to obtain the actual empty trailer weight.
Where possible, obtain the load/deflection curve from the
suspension/spring manufacturer for the specific suspension/
spring combination to find the expected values for this vehicle.
Then, rerun the power-up sequence. Go to Section A.

38

For air suspension system trailers:
Verify/inspect the following:
1.

heck that the load port P42 is connected to the
C
primary suspension air bags at a location as far from
the height control valve as possible. Verify that the
air hose is not kinked.

2.

witch the power to the module ON. Using the ACom
S
Diagnostic Software, open the Pressure screen and
select Start. Read the pressure shown for the load
port (p42). If the pressure value is not as expected,
close the Pressure window and open the Controller
Configuration window. Then, select the Load and
Sensor Configuration tab and view the Load Sensing
panel. Verify that the current Sensing Type is shown as
Internal. If not, change the selection to Internal.

3.

heck that the suspension height control valve is
C
functioning correctly.

4.

Check for air leakage in the suspension system.
•

sing the ACom Diagnostic Software, open the
U
TRSP Sensor screen and select Start. Find the
load (in lbs.) that the sensor is registering, and
verify that the actual trailer load is consistent with
the value found.
• Note the values shown on the screen for the
current load and pressure. Verify that the values
shown on the screen for the empty and laden
weight and pressures are correct. See the NOTE
below.
• Using the ACom Diagnostic Software, where the
value does not appear to be correct, select Modify,
and enter the correct value(s) on the configuration
screen.
NOTE: Use a scale to obtain the actual empty trailer weight
and use a pressure gauge to obtain actual empty trailer
suspension air bag pressure. Where possible, obtain the
load/pressure curve from the suspension manufacturer
for the specific suspension/air bag combination to find the
expected values for this vehicle.
Then, rerun the power-up sequence. Go to Section A.

SECTION G: TROUBLESHOOTING AN AUTOMATIC LIFT AXLE
THAT REMAINS LOWERED
G1 Does
the axle only raise
when the driver’s foot is on the
brake?

Ensure the blue line (ignition power) is
connected at the J560 nose box. Brake
light power is insufficient for an automatic
lift axle.

YES

NO
G2 Is the trailer
loaded such that the axle
should be up?

NO
The axle should remain in lowered
state. There is no issue. End
troubleshooting.

YES

G3 Is power
applied to the system?
The Electronic Control Unit
(ECU) is required to have power for
the Lift Axle Control (LAC) feature to work. Does
the trailer Antilock Braking System (ABS)
indicator lamp on the side of the
trailer turn on and off during
ignition power-up?

NO

See Section C: Troubleshooting the TrailerMounted ABS Indicator Lamp Circuitry and begin
troubleshooting again.

YES

G4
The lift axle mechanism uses
air pressure to lift the axle. If there is
inadequate air in the system, the axle will
not lift. Are the trailer air tanks
fully charged?

NO

Ensure the trailer wheels are chocked since
the following test will release the trailer
spring brakes.
TEST: Charge the trailer tank(s) by pushing
in the red button on the dash. If the axle still
does not lift, continue to section G5.

YES
Go to G5

39

SECTION G: TROUBLESHOOTING AN AUTOMATIC LIFT AXLE
THAT REMAINS LOWERED (CONTINUED)
from previous page

YES

G5 Is the trailer
equipped with a parking brake
override system?

NO

Ensure the trailer wheels are chocked
since the following test will release the
trailer spring brakes.

YES

G 5.1 Is the trailer