Road Stability Advantage
M-593-002
(Aug 2007)

Valid for
All Mack CXU, CHU models equipped with Road Stability Advantage(RSA)

Case description
The MACK Road Stability Advantage (RSA), which is based on the Bendix® ABS-6 Advanced with ESP® (Electronic
Stability Program) System, is an available option on certain MACK model chassis. The RSA system aids the operator
in maintaining control of the vehicle during jackknife or roll-over events by applying select brakes and reducing engine
power as required by the specific situation. The RSA system, which is integral with the anti-lock brake system, uses
the standard ABS components (such as wheel speed sensors and modulator valves) along with a Steering Angle
Sensor (SAS-60™) and a Yaw Rate/Lateral Acceleration Sensor(YAS-60™) package to provide information
concerning vehicle movement to the AdvancedEC-60™ Electronic Control Unit.
Note: Does not apply to Mack Trucks Australia.

SAS-60™ Steering Angle Sensor
SAS-60™ Steering Angle Sensor (CXU, CXN, CHU, CHN, GU, CT7 Column Shown)

The steering angle sensor (SAS-60™) provides vehicle operator steering input by reporting steering wheel positioning
to the ECU. This data is transmitted to the ECU over a dedicated serial communications link, the same
communications link on which data from the yaw rate/ lateral acceleration sensor is transmitted. The ECU provides
power and ground inputs to the SAS-60™ sensor. On CXU, CXN, CHU, CHN, GU and CT7 models, the steering
angle sensor is located at the top of the steering column (as shown in the illustration above), whereas, on CXP and
CTP models, the sensor is located at the bottom of the column.

Caution
Do not replace the OEM steering wheel with an aftermarket steering wheel. Doing so may result in damage to
the steering angle sensor.

Note: When installing an SAS-60™ steering angle sensor on a CXU, CXN, CHU, CHN, GU or CT7 model chassis, the
third tab on the sensor must align with the slot provided in the upper steering column cover.

YAS-60™ Yaw Rate/Lateral Acceleration Sensor
YAS-60™ Yaw Rate/Lateral Acceleration Sensor

Key

Qty.

Part No.

Description

1

1

64MT473M

YAS-60™ Yaw
Rate/Lateral
Acceleration Sensor

2

1

72RU3638M

Mounting bracket,
YAS-60™ sensor,
CXU, CXP, CHU,
CXN, CHN models

1

72RU4106M

Mounting bracket,
YAS-60™ sensor,
GU, CTP, CT7
model chassis

2

26AM12

Screws

3

The Yaw Rate/Lateral Acceleration Sensor (YAS-60™) is mounted on the frame rail in close proximity to the back-ofcab crossmember. This sensor provides the ECU with an indication of vehicle lateral acceleration and rotation around
the vertical axis of the chassis, and is transmitted to the ECU over the same dedicated serial communications link as
the steering angle sensor. The ECU provides power and ground inputs to the yaw rate/lateral acceleration sensor.

Additional Sensors

In addition to the steering angle sensor and yaw rate/lateral acceleration sensor, additional sensors provide brake
application and vehicle load information to the ECU. Brake demand sensors are installed in both the primary and
secondary air brake circuits, and the load sensor is typically installed in one of the air suspension air bags.

Impact of Vehicle Repairs on MACK RSA-Equipped Vehicles
Before delivery to the end user, a “parameter set” tuned for the specific vehicle is loaded into the stability system
Advanced ECU (EC-60™) at the assembly plant. Additionally, the VIN for the chassis is also loaded into the ECU. This
“performance tuning” ensures optimal performance of the MACK RSA system for the specific vehicle. This also means
that the EC- 60™ ECU cannot be used in any other vehicle, even if the vehicle configuration is the same. The VIN
loaded into the ECU must match the specific vehicle.
Note: Should replacement of an EC-60™ ECU be necessary, an ECU with the same “parameter set” for the specific
vehicle (as identified by the VIN) must be ordered. Contact Mack Trucks, Inc. Reliability Engineering at 610-709-3926
prior to placing the order. Replacement of the Advanced EC-60™ ECU with ESP® requires calibration of the SAS60™ and the YAS-60™ sensors.
In most cases, vehicle repairs will not affect function of the MACK RSA system. However, the following repairs require
recalibration of the SAS-60™ sensor after the repair has been made:
Removal and reinstallation or replacement of the SAS-60™ sensor

Caution
Installation of an aftermarket steering wheel may damage the SAS-60™ sensor. It is therefore
recommended that the OEM steering wheel NOT be replaced with an aftermarket wheel.
Any repairs to the steering system or front suspension such as:
– Replacement of front springs
– Replacement of king pins or bushings
– Replacement of the steering gear
– Replacement of the drag link, cross-steering tube or ball sockets
– Replacement of the front spring hangers
– Replacement of the steering column
Front-end alignment
Disconnecting the steering column from the steering gear, or the steering linkage from the steering gear

Warning
Failure to recalibrate the steering angle sensor after performing any of the repairs mentioned above, may
affect proper function of the RSA system, resulting in a loss of vehicle control due to system intervention at
inappropriate times.

The YAS-60™ sensor is mounted on the frame rail, and the sensor must not be removed or repositioned. For any
frame repairs that require removing or loosening the yaw rate/lateral acceleration sensor from its mounted position,
the sensor must be recalibrated once properly reinstalled and resecured to the frame rail in the same position and
orientation.

Vehicle Modifications
Alterations to the vehicle, such as changes to the wheel base (either lengthening or shortening), the addition of an
auxiliary lift axle or removal of a factory-installed auxiliary lift axle, or major body changes, such as conversion of a
tractor to a truck or an axle, suspension or steering system component modification, are NOT allowed, as these

changes will adversely affect performance of the road stability system. Should such changes be unavoidable, the
system must be disabled by having a qualified technician replace the Advanced EC-60™ ECU with a Premium EC60™ ECU.

Warning
Failure to disable the RSA system on a vehicle that has been modified will result in serious vehicle braking
and performance issues, including unnecessary system interventions. These interventions could lead to a loss
of vehicle control.
In addition to disabling the system, any cab labels, such as warning and caution labels relating to the Bendix®
ABS-6 Advanced with ESP® system located on the sun visor must be removed, and notations must be made
to the operator’s manuals so that the vehicle operator has a clear understanding as to which ABS options are
installed on the vehicle.

Location of the yaw rate/lateral acceleration sensor must not be altered. When servicing is required, the sensors must
be replaced with identical components using the original equipment mounting brackets and tightening torque
specifications (15 lb-ft [20 N•m]).
The following additional changes MUST NOT be made to an “as-built” vehicle:
Changes to maximum steering angle (to the left or right)
Changes to steer axle and/or drive axle track width.
Changing the front and/or rear brake drums to drums having a different flange thickness

Tire Size Calibration
The ECU requires a precise rolling circumference ratio between the front steer axle and the rear drive axles for
optimum performance of the system. For this reason, the system continuously calculates the precise ratio and stores
the information in the ECU memory.

Caution
Effectiveness of the RSA system relies on the accuracy of the reported vehicle speed. If major changes to tire
sizes are made, such that changes to the vehicle speedometer/odometer settings are required, the Advanced
EC-60™ ECU must be reprogrammed with the new values by a qualified technician.

Service Information
To accurately, diagnose and repair problems that may develop with the MACK RSA system (Bendix® ABS-6
Advanced with ESP® System), the Bendix ACom Diagnostic Software package is available and can be downloaded
from the Software Zone on the Mack Trucks, Inc. Dealer Portal, or by visiting the Bendix® website at
www.bendix.com. The ACom software communicates with the EC-60™ ECU by way of the J 1587 Diagnostic
Communication port. Use the Kent-Moore Data Link Adapter Kit (tool No. J 38351-D) set to the RP1210A mode, along
with the Kent-Moore 6 pin-to-9 pin Diagnostic Connector Adapter (tool No. J 38500-96a) to connect to the vehicle and
communicate with the Bendix software.
Bendix Commercial Vehicle Systems also maintains a field technical support team who can provide direct support to
field service technicians on troubleshooting and servicing the Bendix ABS and ESP® systems. Calling 1-800-AIRBRAKE will connect the field service technician with a trained Bendix service professional.

Issued by
Technical Service