General Troubleshooting Information
General Troubleshooting InformationEPS 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 or restricted.
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:
^ When the vehicle speed decreases abruptly (by applying the brakes) from above 12 mph (20 km/h) to less than 1 mph (1 km/h), and after abrupt deceleration, the engine speed is above 2,000 rpm for 5 seconds (continuously).
^ The steering wheel is turned for 20 seconds (continuously) when the vehicle speed is than 1 mph (1 km/h), and the engine speed is above 2,000 rpm for at least 10 seconds.
^ The engine speed is above 500 rpm or less and the vehicle speed is above 6 mph (10 km/h) for about 3 seconds (continuously).
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 are 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: Performed 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.
^ Steering diagnosis: Performed during regular diagnosis while turning the 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 or restricts the 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.
^ When DTC 31-01 is detected, the EPS indicator comes on, but the DTC is not memorized.
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).