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EPS Components
General Troubleshooting Information
EPS Indicator
Under normal conditions, the EPS indicator comes on when
the ignition switch is turned to the ON (II) position, then goes
off after the engine is started. This indicates that the bulb and
its circuit are operating correctly.
If 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 light 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 it
keeps the EPS indicator on.
When DTC 12, 16, 17, 18 or 67 is stored in the control unit, the
EPS indicator will stay on until the DTC is erased. When a
problem is detected and the EPS indicator comes on, there are
cases when the indicator stays on until the ignition switch is
turned OFF, and cases when the indicator goes off
automatically when the system returns to normal. Even though
the system is operating normally, the EPS indicator will come
on under the following conditions:
Condition 1:
• The vehicle was traveling at least 12.4 mph (20 km/h), then
• A rapid change in vehicle speed was detected, then
• The vehicle (or the vehicle speed sensor signal) stopped for
at least 5 seconds
• The engine speed was still 1,640 rpm or higher for at least 5
seconds
Condition 2:
After the vehicle (or the vehicle speed sensor signal) has
stopped for at least 10 seconds, yet the engine speed was still
1,640 rpm or higherfor at least 20 seconds.
Condition 3:
When the engine speed is 280 rpm or less, and the vehicle is traveling at
a speed of6.2 mph (10 km/h) or more for 3 seconds.
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 (DTC)
• If the CPU cannot be activated, or it fails, 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
occurrence is memorized.
• The DTCs are indicated repeatedly until the ignition switch is
turned OFF.
• If the DTC is not memorized, the EPS indicator blinks.
17-18
• The DTCs are memorized in the EEPROM (non-volatile
memory) therefore the memorized DTCs cannot be erased
by disconnecting the battery. Perform the specified
procedures to clear DTCs.
Self-diagnosis
Self-diagnosis can be classified into two categories:
Initial diagnosis: perforrned right after the engine
starts and until the EPS indicator goes off.
Regular diagnosis: performed right after the 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 DTC.
3. Stops power assist and manual steering operation
begins.
NOTE:
• When DTC 23 (a problem with the circuit for
engine speed signal) is detected, the power
assist will return to normal when the vehicle
speed is 0.62 mph (1 km/h) or above.
For DTCs 22, 23, 64, or 66 the EPS indicator goes
off automatically when the system returns to
normal. For all other codes, the EPS indicator
goes off when the system is OK after the ignition
switch is turned from OFF to ON (II).
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
consumption in the EPS motor. The increase of electric
current causes the motor to heat up. 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, and the motor
cools, the control unit will restore the power assist
gradually until it's fully restored (after approximately 15
minutes maximum).
•
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Troubleshooting
