TGB EST 1000, Service Manual, Page: 218 / 269

7-2. ELECTRIC POWER STEERING
7-2-2
(EPS) Electric Power Steering
GENERAL
During assembly/installation, use the torque
values and service products as in the exploded
view.
Clean threads before applying thread locker.
WARNING
Torque wrench tightening specifications
must strictly be adhered to.
Locking devices (e.g.: locking tabs, elastic
stop nuts, self-locking fasteners, cotter pin,
etc.) must be replaced.
Hoses, cables or locking ties removed during a
procedure must be reinstalled as per factory
standards.
SYSTEM DESCRIPTION
The Electric Power Steering (EPS) provides a
computer controlled, variable power assist,
achieved by an electric motor to optimize the
amount of steering input required by the rider.
The EPS system uses the following parameters
to determine how much steering assist it
provides:
- Electrical system voltage.
- Vehicle speed.
- EPS shaft torque sensor input.
The amount of steering assist provided is
dependent on the handlebar effort (steering
torque), electrical power available, and vehicle
speed.
When handlebar is in the straight ahead
position, there is no steering assist.
Steering torque may also come from the wheels
due to rough terrain. Steering kickback is
reduced while providing feedback to the driver.
The greater the power steering assist, the
greater the load on the electrical system.
When electrical system is under high load
(battery not at full charge, operating the vehicle
for prolonged periods of time at slow speed and
low RPM which, requires higher power steering
assist), the battery power reserve will gradually
decrease. This further increase the load on the
charging system and the electrical system
voltage will drop. As system voltage drops, so
does power steering assist.
NOTE: It is important to maintain the battery at
a full state of charge to ensure proper EPS
operation. The magneto output is 650 watts to
minimize battery drain and system voltage
drop.
EPS Assist Mode
The EPS system provides two rider selectable
modes of operation.
ESP MAX provides maximum steering assist
for technical low speed riding in rough or
muddy terrain or for touring.
EPS MIN provides less steering assist for
increased feedback and trail riding.
De-rating Explanation
De-rating is an internal protection system
integrated in the EPS electrical module.
This system protects the electrical components
when EPS works too hard and internal
temperature reaches a critical level.
It also protects electronics when current ripples
in the system are too high. These current
ripples can be caused by:
- Bad grounds.
- Defective stator or bad stator output wires
connection.
- Failed regulator.
- High electrical loads.