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 LED and its circuit are operating correctly. If there is a failure in the system after the engine is started, the EPS indicator will stay on, and the power assist is turned off.

When the 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 it keeps the EPS indicator on.

When DTC 51-01, 51-02 or 51-06 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:
^ The vehicle speed decreases abruptly from 12 mph (20 km/h) or more (by applying brake), and it is less than 1 mph (1 km/h) and engine speed is 2,000 rpm or above for 5 seconds (continuously) after the abrupt deceleration.
^ While turning the steering wheel with the vehicle speed of 1 mph (1 km/h) or less for 20 seconds, and the engine speed is 2,000 rpm or above for at least 10 seconds.
^ When the engine speed is 500 rpm or less, and the vehicle is traveling at a speed of 6 mph (10 km/h) or more for about 3 seconds.

To determine the actual cause of the problem, question the customer about the conditions during which the problem occurred, 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 lowest DTC is indicated first. The DTCs a re indicated in ascending order, not in the order that they occurred.
^ The DTCs are memorized in the EEPROM (nonvolatile 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 three categories:
^ Initial diagnosis: Done right after the engine starts and until the EPS indicator goes off.
^ Regular diagnosis: Done right after the initial diagnosis until the ignition switch is turned OFF.
^ Steering diagnosis: Done during regular diagnosis while turning steering wheel.

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 resumes.

NOTE: For DTCs 11-01, 11-02, 12-01, 21-01, 21-02, 22-01 and 35-04 the EPS indicator will go off automatically, and the system returns to normal.

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 about 8 minutes).

Torque Sensor Neutral Position
The EPS control unit stores the torque sensor neutral position in the EEPROM. The torque sensor neutral position must be memorized whenever the gearbox, the motor, or the EPS control unit is replaced.

NOTE: The torque sensor neutral position is not effected when erasing the DTCs.