Electronic Power Steering System (Diagnostic Codes): Overview Lexus GS III 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.

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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. Resistance Tester connection (Symbols) Condition Specified condition C1-1 (INCS) - C4-8 (INCS) Always Below 1 ohms C1-2 (INSN) - C4-7 (INSN) Always Below 1 ohms C1-4 (TRQV) - C4-1 (TRQV) Always Below 1 ohms C1-5 (OUCS) - C4-10 (OUCS) Always Below 1 ohms C1-6 (OUSN) - C4-9 (OUSN) Always Below 1 ohms C1-7 (TQG2) - C4-14 (TQG2) Always Below 1 ohms C1-8 (TQG1) - C4-12 (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 LINK ASSEMBLY (TORQUE SENSOR) Measure the resistance according to the value(s) in the table below. 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 link assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor, and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . If replacing the power steering link assembly, perform VGRS actuator angle initialization and VGRS actuator angle neutral calibration after wheel alignment adjustment. Refer to «INITIALIZATION»(ref-382810-S14733650782011012800000) for INITIALIZATION, refer to «CALIBRATION»(ref-382810-S39353253692011012800000) for CALIBRATION). NG --> REPLACE POWER STEERING LINK ASSEMBLY OK: Go to next step
3. REPLACE POWER STEERING ECU ASSEMBLY Replace the power steering ECU assembly. Refer to «REMOVAL»(ref-382577-S01085502732011012800000) . NEXT: Go to next step
4. INITIALIZE ROTATION ANGLE SENSOR AND CALIBRATE TORQUE SENSOR ZERO POINT Initialize the rotation angle sensor and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . NEXT: Go to next step
5. RECONFIRM DTC Check for DTCs. Refer to «DTC CHECK / CLEAR»(ref-382573-S06970880742011012800000) . Is DTC C1511, C1512 or C1513 output? OK DTC is not output. NOTE: If replacing the power steering link assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor, and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . If replacing the power steering link assembly, perform VGRS actuator angle initialization and VGRS actuator angle neutral calibration after wheel alignment adjustment. Refer to «INITIALIZATION»(ref-382810-S14733650782011012800000) for INITIALIZATION, refer to «CALIBRATION»(ref-382810-S39353253692011012800000) for CALIBRATION). NG --> REPLACE POWER STEERING LINK ASSEMBLY OK --> END

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

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

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

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1. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - POWER STEERING MOTOR) Disconnect the C4 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. Resistance Tester connection (Symbols) Condition Specified condition C4-5 (U) - C3-3 (U) Always Below 1 ohms C4-11 (V) - C3-2 (V) Always Below 1 ohms C4-6 (W) - C3-1 (W) Always Below 1 ohms C4-5 (U) - Body ground Always 10 kohms or higher C4-11 (V) - Body ground Always 10 kohms or higher C4-6 (W) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
2. INSPECT POWER STEERING LINK ASSEMBLY (POWER STEERING MOTOR) Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) 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 NOTE: If replacing the power steering link assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor, and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . If replacing the power steering ECU assembly, initialize the rotation angle sensor and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . If replacing the power steering link assembly, perform VGRS actuator angle initialization and VGRS actuator angle neutral calibration after wheel alignment adjustment. Refer to «INITIALIZATION»(ref-382810-S14733650782011012800000) for INITIALIZATION, refer to «CALIBRATION»(ref-382810-S39353253692011012800000) for CALIBRATION). NG --> REPLACE POWER STEERING LINK 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.

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1. CHECK POWER STEERING EARTH WIRE (POWER STEERING LINK ASSEMBLY - BODY GROUND) Check the installation condition of the power steering earth wire connected to the power steering link assembly. OK The power steering earth wire is securely installed to the power steering link 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 link assembly. Disconnect the C4 connector from the power steering ECU. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition C2-1 (RZSN) - C4-4 (RZSN) Always Below 1 ohms C2-2 (RZG) - C4-13 (RZG) Always Below 1 ohms C2-3 (RZV) - C4-2 (RZV) Always Below 1 ohms C2-4 (RZCS) - C4-3 (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 LINK ASSEMBLY (MOTOR ROTATION ANGLE SENSOR) Measure the resistance according to the value(s) in the table below. 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 link assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor, and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . If replacing the power steering link assembly, perform VGRS actuator angle initialization and VGRS actuator angle neutral calibration after wheel alignment adjustment. Refer to «INITIALIZATION»(ref-382810-S14733650782011012800000) for INITIALIZATION, refer to «CALIBRATION»(ref-382810-S39353253692011012800000) for CALIBRATION). NG --> REPLACE POWER STEERING LINK ASSEMBLY OK: Go to next step
4. REPLACE POWER STEERING ECU ASSEMBLY Replace the power steering ECU assembly. Refer to «REMOVAL»(ref-382577-S01085502732011012800000) . NEXT: Go to next step
5. INITIALIZE ROTATION ANGLE SENSOR AND CALIBRATE TORQUE SENSOR ZERO POINT Initialize the rotation angle sensor and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . NEXT: Go to next step
6. RECONFIRM DTC Check for DTCs. Refer to «DTC CHECK / CLEAR»(ref-382573-S06970880742011012800000) . Is DTC C1528 output? OK DTC is not output. NOTE: If replacing the power steering link assembly, clear the rotation angle sensor calibration value, initialize the rotation angle sensor, and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . If replacing the power steering link assembly, perform VGRS actuator angle initialization and VGRS actuator angle neutral calibration after wheel alignment adjustment. Refer to «INITIALIZATION»(ref-382810-S14733650782011012800000) for INITIALIZATION, refer to «CALIBRATION»(ref-382810-S39353253692011012800000) for CALIBRATION). NG --> REPLACE POWER STEERING LINK ASSEMBLY OK --> END

If the power steering ECU assembly detects these DTCs, it will shut off the 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.

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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.

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1. INSPECT FUSES (ECU-B, EPS FUSE) Check for continuity of the ECU-B and EPS fuses. OK Continuity NG --> REPLACE FUSE OK: Go to next step
2. INSPECT ELECTRIC POWER STEERING RELAY Remove the EPS relay from the engine room R/B No. 1. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Specified condition 3 - 5 10 kohms or higher 3 - 5 Below 1 ohms (When battery voltage is applied to terminals 1 and 2) NG --> REPLACE ELECTRIC POWER STEERING RELAY OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (EPS RELAY - BATTERY) Measure the voltage according to the value(s) in the table below. Voltage Tester connection Condition Specified condition 1 - Body ground Always 10 to 14 V 5 - Body ground Always 10 to 14 V NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
4. CHECK HARNESS AND CONNECTOR (EPS RELAY - POWER STEERING ECU ASSEMBLY) Disconnect the A23 connector from the power steering ECU assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Condition Specified condition A23-4 (PIG) - 3 Always Below 1 ohms A23-11 (RLY) - 2 Always Below 1 ohms A23-4 (PIG) - Body ground Always 10 kohms or higher A23-11 (RLY) - Body ground Always 10 kohms or higher A23-4 (PIG) - A23-11 (RLY) Always 1 Mohms or higher NOTE: If replacing the power steering ECU assembly, initialize the rotation angle sensor and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE POWER STEERING ECU ASSEMBLY

The power steering ECU assembly communicates with the supervisory microcomputer in the steering control ECU via local CAN communication. If data used for cooperative control via local CAN communication is incorrect, the EPS cooperative control function will stop immediately.

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1. CHECK HARNESS AND CONNECTOR (POWER STEERING ECU ASSEMBLY - STEERING CONTROL ECU) Disconnect A23 connector from the power steering ECU assembly. Disconnect A40 connector from the steering control ECU. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition A23-1 (CAN+) - A40-4 (CAN+) Engine switch off Below 1ohms A23-8 (CAN-) - A40-9 (CAN-) Engine switch off Below 1ohms A23-1 (CAN+) - Body ground Engine switch off 10 k or higher A23-8 (CAN-) - Body ground Engine switch off 10 k or higher A40-4 (CAN+) - A40-10 (+BI) Engine switch off 10 k or higher A40-9 (CAN-) - A40-10 (+BI) Engine switch off 10 k or higher NG --> REPAIR OR REPLACE LOCAL CAN COMMUNICATION LINE OR CONNECTOR OK --> REPLACE STEERING CONTROL ECU

The power steering ECU assembly outputs this DTC when it determines that 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 and 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 U0129 only, it adjusts the amount of power assistance for a speed of 100 km/h (62 mph) and continues system control.

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The troubleshooting procedure for a situation in which no DTCs are output but the P/S warning light is always on is specified here. The P/S warning light remains on when there is an open in the IG circuit inputting power source voltage to the power steering ECU assembly.

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1. CHECK HARNESS AND CONNECTOR Check the indication condition of the P/S warning light while by wiggling the power steering ECU assembly connector and wire harness up and down, and right and left. OK P/S 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 OK: Go to next step
3. INSPECT MULTIPLEX COMMUNICATION SYSTEM (BEAN) 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 (BEAN) OK: Go to next step
4. INSPECT FUSE (ECU-IG LH) Remove the ECU-IG LH fuse from the cowl side J/B LH. Check for continuity of the ECU-IG LH fuse. OK Continuity NG --> REPLACE FUSE OK: Go to next step
5. INSPECT POWER STEERING ECU ASSEMBLY Disconnect the A23 connector from the power steering ECU assembly. Measure the voltage according to the value(s) in the table below. Voltage Tester connection (Symbols) Condition Specified condition A23-9 (IG) - A23-5 (PGND) Engine switch on (IG) 10 to 14 V OK --> See step 7 NG: 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. Resistance Tester connection (Symbols) Condition Specified condition A23-5 (PGND) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER STEERING ECU ASSEMBLY - BATTERY)
7. REPLACE POWER STEERING ECU ASSEMBLY NOTE: If replacing the power steering ECU assembly, initialize the rotation angle sensor and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-382573-S05048789232011012800000) . NEXT: Go to next step
8. CHECK P/S WARNING LIGHT Check the P/S warning light status on the combination meter. Standard The P/S warning light is off. OK --> END NG --> REPLACE PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE