POWER STEERING SYSTEM PS Warning Light Remains ON

DESCRIPTION

If the power steering ECU detects a malfunction, the EPS warning light comes on. At this time, the power steering ECU stores a DTC in its memory.

WIRING DIAGRAM

A01IS0HE01

INSPECTION PROCEDURE

Note


  • If the power steering ECU assembly is replaced, perform the assist map writing Click here.

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.

Tech Tips

When the power supply voltage to the power steering ECU (terminals IG and PIG) drops, required steering effort increases and the EPS warning light turns on.

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR


    1. Turn the ignition switch to ON.

    2. Check the indication condition of the EPS warning light by wiggling the power steering ECU connector and wire harness up and down, and right and left.

      OK
      EPS warning light indication condition does not change.

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK FOR DTC (CAN COMMUNICATION SYSTEM)


    1. Check for DTCs Click here.

      OK
      DTC is not output.

    NG

    GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING) Click here

    OK

  3. READ VALUE USING INTELLIGENT TESTER (IG POWER SUPPLY)


    1. Turn the ignition switch off.

    2. Connect the intelligent tester to the DLC3.

    3. Turn the ignition switch to ON.

    4. Turn the intelligent tester on.

    5. Enter the following menus: Chassis / EMPS / Data List.

      EMPS
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      IG Power Supply

      ECU power source voltage/

      Min.: 0.0000 V

      Max.: 20.1531 V

      		 11 to 14 V The ignition switch is ON.
      OK
      The normal condition value is displayed the intelligent tester.

    NG

    Click here

    OK

  4. READ VALUE USING INTELLIGENT TESTER (PIG POWER SUPPLY)


    1. Turn the ignition switch off.

    2. Connect the intelligent tester to the DLC3.

    3. Start the engine.

    4. Turn the intelligent tester on.

    5. Enter the following menus: Chassis / EMPS / Data List.

      EMPS
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      PIG Power Supply

      Power source voltage to active motor/

      Min.: 0.0000 V

      Max.: 20.1531 V

      		 11 to 14 V The engine is running and power steering is operating.
      OK
      The normal condition value is displayed the intelligent tester.

    NG

    Click here

    OK

  5. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (METER / GAUGE SYSTEM)


    1. Perform the Active Test of the combination meter using the intelligent tester Click here.

      Combination Meter
      Tester Display Test Part Control Range Diagnostic Note
      Indicat. EPS EPS warning light ON or OFF Perform the test with the vehicle stopped and the engine idling.

    2. Check that the EPS warning light operates in accordance with the Active Test.

      Tech Tips

      Reconnect the connectors and restore the vehicle to its previous condition before checking the combination meter.


    NG

    REPLACE COMBINATION METER ASSEMBLY Click here

    OK

    REPLACE POWER STEERING ECU ASSEMBLY Click here

  6. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU - BATTERY)


    1. Turn the ignition switch off.

    2. A01IPN0E02
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Power Steering ECU)

      Disconnect the H49 power steering ECU connector.

    3. Turn the ignition switch to ON.

    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      H49-5 (IG) - Body ground Ignition switch ON 11 to 14 V
      Result
      Result Proceed to
      OK A
      NG w/o Stop and start system B
      w/ Stop and start system C

    B

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    C

    GO TO STOP AND START SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING) Click here

    A

  7. CHECK GROUND BOLT AND WIRE HARNESS


    1. Turn the ignition switch off.

    2. Check that the ground bolt and wire harness are installed correctly Click here.

      OK
      Ground bolt and wire harness are installed correctly.

    NG

    INSTALL GROUND BOLT AND WIRE HARNESS CORRECTLY Click here

    OK

  8. CHECK TERMINAL SCREW AND ECU WIRE SUB-ASSEMBLY


    1. Remove the power terminal cover from the power steering ECU Click here.

    2. Check that the z21 terminal screw and ECU wire sub-assembly are installed correctly Click here.

      OK
      Terminal screw and ECU wire sub-assembly are installed correctly.

    NG

    INSTALL TERMINAL SCREW AND ECU WIRE SUB-ASSEMBLY CORRECTLY Click here

    OK

  9. CHECK ECU WIRE SUB-ASSEMBLY


    1. A01IPKXE01
      Text in Illustration
      *1 ECU Wire Sub-assembly

      Remove the z21 terminal screw from the power steering ECU Click here.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      z21-1 (PGND) - Body ground Always Below 1 Ω

    NG

    REPLACE ECU WIRE SUB-ASSEMBLY Click here

    OK

    REPLACE POWER STEERING ECU ASSEMBLY Click here

  10. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU - BATTERY)


    1. Turn the ignition switch off.

    2. A01ITNXE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to ECU Wire Sub-assembly)

      Disconnect the Az1 power steering ECU connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      Az1-1 - Body ground Always 11 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  11. CHECK GROUND BOLT AND WIRE HARNESS


    1. Turn the ignition switch off.

    2. Check that the ground bolt and wire harness are installed correctly Click here.

      OK
      Ground bolt and wire harness are installed correctly.

    NG

    INSTALL GROUND BOLT AND WIRE HARNESS CORRECTLY Click here

    OK

  12. CHECK TERMINAL SCREW AND ECU WIRE SUB-ASSEMBLY


    1. Remove the power terminal cover from the power steering ECU Click here.

    2. Check that the z21 and z21 terminal screws and ECU wire sub-assembly are installed correctly Click here.

      OK
      Terminal screws and ECU wire sub-assembly are installed correctly.

    NG

    INSTALL TERMINAL SCREW AND ECU WIRE SUB-ASSEMBLY CORRECTLY Click here

    OK

  13. CHECK ECU WIRE SUB-ASSEMBLY


    1. A01IPW8E01
      Text in Illustration
      *1 ECU Wire Sub-assembly

      Remove the z21 and z22 terminal screws from the power steering ECU Click here.

    2. Disconnect the Az1 connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      z21-1 (PGND) - Body ground Always Below 1 Ω
      z22-1 (PIG) - Az1-1 Always Below 1 Ω
      z21-1 (PGND) - z22-1 (PIG) Always 10 kΩ or higher

    NG

    REPLACE ECU WIRE SUB-ASSEMBLY Click here

    OK

    REPLACE POWER STEERING ECU ASSEMBLY Click here