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EPS Gomponents
General Troubleshooting Information
EPS Indicator
Under normal conditions. the EPS indicator comes on
when the ignition switch is turned to the ON (ll) position,
then goes off after the engine is started. This indicates
that the bulb and its circuit are operating correctly.
lf there is any trouble in the system after the engine is
started, the EPS indicator will stay on, and the power
assist is turned off.
When EPS indicator comes on, the control unit
memorizes the DTC. In this case, the control unit will
not activate the EPS system after the engine starts
again, but il keeps the EPS indicator on.
When DTC 11, 12, ot 13 is stored in the control unit, the
EPS indicator will stay on until the DTC is erased. Even
though the system is operating normally, the EPS
indicator will come on under the following conditions:
. When the vehicle is barely moving, 0.62 mph (1 km/h)
or stopped, and the engine speed is 2.000 rpm or
higher for about 3 minutes.
. When the engine speed is 500 rpm or less, and the
vehicle is travelling at a speed of 6.2 mph (10 km/h)
or more for about 3 minutes.
To determine the actual cause of the problem. question
the customer about the conditions during which the
problem occured, taking the above conditions into
consideration.
Diagnostic Trouble Code (DTCI
. lf the CPU cannot be activated. or itfails, the EPS
indicator comes on, but the DTC is not memorized.
. The memory can hold any number of DTCS. However,
when the same DTC is detected more than once, the
most recent DTC is written over the prior DTC.
therefore only one occurance is memorized.
. The lowest DTC is indicated first. The DTCs are
indicated in ascending order, not in the orderthat
they occurred.
. The DTCS are memorized in the EEPROM (non-
volatile memory) therefore the memorized DTCs
cannot be erased by disconnecting the battery.
Perform the soecified Drocedures to ciear DTCS.
Self-diagnosis
Self-diagnosis can be classified into two categories:
. Initial diagnosis: performed right after the engine
starts and untilthe EPS indicator goes off.
. Regular diagnosis: performed right afterthe initial
diagnosis until the ignition switch is turned OFF.
The EPS control unit performs the following functions
when a problem is detected by self-diagnosis:
'1.
Turns on the EPS indicator.
2. Memorizes the oTC.
3. Stops power assist and manual steering operation
resumes.
NOTE:
. When DTC 23 (a problem with the circuitfor
engine speed signal) is detected, the power
assist will return to normal when the vehicle
speed is 6.2 mph (10 km/h) or above.
, Fot OfCs21,22, and 23the EPS indicatorwill go
off automaticallV, and the system returns to
n o r m a l .
Restriction on Power Assist Operation
Repeated extreme steering force. such as turning the
steering wheel continuously back-and-forth with the
vehicle stopped. causes an increase of power
consumotion in the EPS motor. The increase of electric
current causes the motor to heat uo. Because this heat
adversely affects the system. the control unit monitors
the electric current of the motor.
When the control unit detects heat build-up in the motor.
it reduces the electric current to the motor gradually to
protect the system, and it restricts the power assist
operation. The EPS indicator does not come on during
this function.
When steering torque is not applied to the steering
wheel, or when the ignition is turned off, the control
unit will restore the power assist gradually until it's fully
restored (after about 8 minutes).
EPS Control Unit Noise
A relay sound or "click" can be heard from the EPS
control unit about 30 seconds after the ionition switch is
turned off. This sound is normal.
Torque Sensor Neutral Position
The EPS control unit stores the torque sensor neutral
position in the EEPROM. Memorize the torque sensor
neutral position whenever the gearbox is removed and
installed, or when the lorque sensor or EPS control unit
is reDlaced.
NOTE: The toroue sensor neutral oosition is not
effected when erasing the DTCs.
17-18
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Troubleshooting
