Electronic Power Steering (Diagnostic Codes & Symptom Tests): Overview Lexus IS II facelift

DESCRIPTION

The torque sensor converts rotation torque input to the steering wheel into an electrical signal and sends it to the ECU. Based on this signal, the ECU detects steering effort.

Scheme 10

Scheme 11

Scheme 12

1. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - TORQUE SENSOR) Disconnect the C4 connector from the power steering ECU assembly. Disconnect the C1 connector from the torque sensor. Measure the resistance according to the value(s) in the table below. Standard resistance Tester connection (Symbols) Condition Specified condition C1-1 (INCS) - C4-10 (INCS) Always Below 1 ohms C1-2 (INSN) - C4-9 (INSN) Always Below 1 ohms C1-4 (TRQV) - C4-4 (TRQV) Always Below 1 ohms C1-5 (OUCS) - C4-12 (OUCS) Always Below 1 ohms C1-6 (OUSN) - C4-11 (OUSN) Always Below 1 ohms C1-7 (TQG2) - C4-13 (TQG2) Always Below 1 ohms C1-8 (TQG1) - C4-6 (TQG1) Always Below 1 ohms C1-1 (INCS) - Body ground Always 10 kohms or higher C1-2 (INSN) - Body ground Always 10 kohms or higher C1-4 (TRQV) - Body ground Always 10 kohms or higher C1-5 (OUCS) - Body ground Always 10 kohms or higher C1-6 (OUSN) - Body ground Always 10 kohms or higher C1-7 (TQG2) - Body ground Always 10 kohms or higher C1-8 (TQG1) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
2. INSPECT POWER STEERING GEAR ASSEMBLY (TORQUE SENSOR) Measure the resistance according to the value(s) in the table below. Standard resistance Tester connection (Symbols) Condition Specified condition C1-1 (INCS) - C1-7 (TQG2) Always 90 to 170 ohms C1-2 (INSN) - C1-7 (TQG2) Always 300 to 430 ohms C1-4 (TRQV) - C1-8 (TQG1) Always 4 to 14 ohms C1-5 (OUCS) - C1-7 (TQG2) Always 90 to 170 ohms C1-6 (OUSN) - C1-7 (TQG2) Always 300 to 430 ohms NOTE: If replacing the power steering gear assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor value, and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NG --> REPLACE POWER STEERING GEAR ASSEMBLY OK: Go to next step
3. REPLACE POWER STEERING ECU ASSEMBLY Replace the power steering ECU assembly . Refer to «REMOVAL»(ref-387370-S28199339522011022400000) . NEXT: Go to next step
4. INITIALIZE ROTATION ANGLE SENSOR AND CALIBRATE TORQUE SENSOR ZERO POINT Initialize the rotation angle sensor value and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NEXT: Go to next step
5. RECONFIRM DTC Check for DTCs . Refer to «DTC CHECK / CLEAR»(ref-387428-S03200748582011022400000) . Result DTC Condition Proceed to DTC is not output A DTC C1511, C1512, or C1513 is output B NOTE: If replacing the power steering gear assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor value, and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . B --> REPLACE POWER STEERING GEAR ASSEMBLY A --> END

These DTCs do not indicate a malfunction. The power steering ECU assembly outputs these DTCs when it determines that rotation angle sensor value initialization and torque sensor zero point calibration have not been performed. When IG terminal voltage is 9 V or less rotation angle sensor initialization and torque sensor zero point calibration cannot be performed.

These DTCs do not indicate a malfunction. The power steering ECU assembly outputs these DTCs when it determines that rotation angle sensor value initialization and torque sensor zero point calibration are incomplete.

The power steering ECU assembly supplies current to the power steering motor through this circuit.

Scheme 13

Scheme 14

Scheme 15

1. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - POWER STEERING MOTOR) Disconnect the C5 connector from the power steering ECU assembly. Disconnect the C3 connector from the power steering motor. Measure the resistance according to the value(s) in the table below. Standard resistance Tester Connection Condition Specified Condition C5-1 (V) - C3-2 (V) Always Below 1 ohms C5-2 (U) - C3-3 (U) Always Below 1 ohms C5-3 (W) - C3-1 (W) Always Below 1 ohms C5-1 (V) - Body ground Always 10 kohms or higher C5-2 (U) - Body ground Always 10 kohms or higher C5-3 (W) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
2. INSPECT POWER STEERING GEAR ASSEMBLY (POWER STEERING MOTOR) Measure the resistance according to the value(s) in the table below. Standard resistance Tester Connection Condition Specified Condition C3-3 (U) - C3-2 (V) Always Below 1 ohms C3-2 (V) - C3-1 (W) Always Below 1 ohms C3-1 (W) - C3-3 (U) Always Below 1 ohms C3-3 (U) - Motor body Always 10 kohms or higher C3-2 (V) - Motor body Always 10 kohms or higher C3-1 (W) - Motor body Always 10 kohms or higher NOTE: If replacing the power steering gear assembly, clear the rotation angle sensor value calibration value, initialize the rotation angle sensor, and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NOTE: If replacing the power steering ECU assembly, initialize the rotation angle sensor value and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NG --> REPLACE POWER STEERING GEAR ASSEMBLY OK --> REPLACE POWER STEERING ECU ASSEMBLY

The motor rotation angle sensor detects the motor rotation angle and sends this information to the power steering ECU assembly.

Scheme 16

Scheme 17

Scheme 18

1. CHECK POWER STEERING EARTH WIRE (POWER STEERING GEAR ASSEMBLY - BODY GROUND) Check the installation condition of the power steering earth wire connected to the power steering gear assembly. OK The power steering earth wire is securely installed to the power steering gear assembly and body ground. NG --> REINSTALL POWER STEERING EARTH WIRE OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - MOTOR ROTATION ANGLE SENSOR) Disconnect the C2 connector from the power steering motor assembly. Disconnect the C4 connector from the power steering ECU. Measure the resistance according to the value(s) in the table below. Standard resistance Tester connection (Symbols) Condition Specified condition C2-1 (RZSN) - C4-7 (RZSN) Always Below 1 ohms C2-2 (RZG) - C4-1 (RZG) Always Below 1 ohms C2-3 (RZV) - C4-3 (RZV) Always Below 1 ohms C2-4 (RZCS) - C4-8 (RZCS) Always Below 1 ohms C2-1 (RZSN) - Body ground Always 10 kohms or higher C2-2 (RZG) - Body ground Always 10 kohms or higher C2-3 (RZV) - Body ground Always 10 kohms or higher C2-4 (RZCS) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
3. INSPECT POWER STEERING GEAR ASSEMBLY (MOTOR ROTATION ANGLE SENSOR) Measure the resistance according to the value(s) in the table below. Standard resistance Tester connection (Symbols) Condition Specified condition C2-1 (RZSN) - C2-2 (RZG) Always 50 to 140 ohms C2-3 (RZV) - C2-2 (RZG) Always 15 to 45 ohms C2-4 (RZCS) - C2-2 (RZG) Always 50 to 140 ohms NOTE: If replacing the power steering gear assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor value, and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NG --> REPLACE POWER STEERING GEAR ASSEMBLY OK: Go to next step
4. REPLACE POWER STEERING ECU ASSEMBLY Replace the power steering ECU assembly . Refer to «REMOVAL»(ref-387370-S28199339522011022400000) . NEXT: Go to next step
5. INITIALIZE ROTATION ANGLE SENSOR AND CALIBRATE TORQUE SENSOR ZERO POINT Initialize the rotation angle sensor value and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NEXT: Go to next step
6. RECONFIRM DTC Check for DTCs . Refer to «DTC CHECK / CLEAR»(ref-387428-S03200748582011022400000) . Result DTC Condition Proceed to DTC is not output A DTC C1528 is output B NOTE: If replacing the power steering gear assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor value, and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . B --> REPLACE POWER STEERING GEAR ASSEMBLY A --> END

If the power steering ECU assembly detects these DTCs, it will shut off the motor current sensor, power source relay, motor relay circuit (built into the power steering ECU assembly) and stop power assistance. However , power assistance will continue if DTC C1533 or C1534 is output.

The power steering ECU assembly receives vehicle speed signals from the skid control ECU via CAN communication. The ECU provides appropriate assisting force in accordance with the vehicle speed, based on the signals.

If the ECU detects this DTC, it adjusts the amount of power assistance for a speed of 100 km/h (62 mph) and continues the system control.

If the power steering ECU assembly determines that there is a malfunction in the IG circuit inside the ECU, it outputs this DTC. This DTC is not output when there is an open circuit in the wire harness connected to terminal IG or a battery voltage drop.

This circuit supplies power to drive the power steering motor.

Scheme 19

Scheme 20

Scheme 21

1. INSPECT FUSE (EPS FUSE) Remove the EPS fuse from the No. 1 engine room relay block. Check for continuity of the EPS fuses. OK Continuity NG --> REPLACE FUSE OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - BATTERY) Disconnect the A31 connector from the power steering ECU assembly. Measure the voltage according value(s) in the table below. Standard voltage Tester Connection Condition Specified Condition A31-4 (PIG) - Body ground Always 10 to 14 V NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - BODY GROUND) Measure the resistance according value(s) in the table below. Standard resistance Tester Connection Condition Specified Condition A31-5 (PGND) - Body ground Always Blow 1 ohms NOTE: If replacing the power steering ECU assembly, initialize the rotation angle sensor value and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE POWER STEERING ECU ASSEMBLY

The power steering ECU assembly outputs this DTC when it determines that the assist map is not written in the ECU.

HINT

The assist map is data written in the power steering ECU assembly to control the degree of assistance. The assist map is selected based on the vehicle's specified communication data (designation and grade package information).

The power steering ECU assembly receives signals from the ECM, skid control ECU, and steering control ECU via CAN communication.

HINT

1. When two or more DTCs starting with "U" are output simultaneously, inspect the connectors and wire harness of each ECU.
2. If the power steering ECU assembly detects DTC U0121 only, it adjusts the amount of power assistance for a speed of 100 km/h (62 mph) and continues system control.

The power steering ECU is connected to the combination meter via CAN and multiplex communications. If any of the following are detected, the PS warning light remains on.

1. The power steering ECU connectors are disconnected from the power steering ECU.
2. There is a malfunction in the power steering ECU internal circuit.
3. There is an open in the harness between the combination meter and power steering ECU assembly.

Scheme 22

Scheme 23

1. CHECK HARNESS AND CONNECTOR Check the indication condition of the PS warning light while by wiggling the power steering ECU assembly connector and wire harness up and down, and right and left. OK PS warning light indication condition does not change. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
2. INSPECT CAN COMMUNICATION SYSTEM Using the Techstream, check for DTCs and confirm that there are no problems in the CAN communication system. OK DTCs are not output. NG --> GO TO «CAN COMMUNICATION SYSTEM»(ref-387391-S03462946972011022400000) OK: Go to next step
3. INSPECT MULTIPLEX COMMUNICATION SYSTEM Using the Techstream, check for DTCs and confirm that there are no problems in the multiplex communication system (BEAN). OK DTCs are not output. NG --> GO TO MULTIPLEX COMMUNICATION SYSTEM OK: Go to next step
4. INSPECT FUSE Remove the ECU-IG LH fuse from the cowl side J/B LH. Check for continuity of the ECU-IG LH fuse. OK Below 1 ohms NG --> REPLACE FUSE OK: Go to next step
5. INSPECT POWER STEERING ECU ASSEMBLY Disconnect the A31 connector from the power steering ECU assembly. Measure the voltage according to the value(s) in the table below. Standard voltage Tester Connection Condition Specified Condition A31-9 (IG) - Body ground Engine switch on (IG) 10 to 14 V NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
6. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - BODY GROUND) Measure the resistance according to the value(s) in the table below. Standard resistance Tester Connection Condition Specified Condition A31-5 (PGND) - Body ground Engine switch on (IG) Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
7. INSPECT COMBINATION METER ASSEMBLY Connect the Techstream (with CAN VIM ) to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Perform the Active Test. Enter the following menus: Body Electrical / Combination Meter / Active Test. COMBINATION METER Tester Display Test Part Control Range Diagnostic Note Indicat. EPS PS indicator light Indicator light ON / OFF - OK PS indicator light comes on. NOTE: If replacing the power steering ECU assembly, initialize the rotation angle sensor value and calibrate the torque sensor zero point . Refer to «CALIBRATION»(ref-387428-S08117833522011022400000) . NG --> REPLACE COMBINATION METER ASSEMBLY OK --> REPLACE POWER STEERING ECU ASSEMBLY