Variable Gear Ratio Steering System (Diagnostic Codes & Symptom Tests): Diagnosis Lexus GS III facelift

INSPECTION PROCEDURE

HINT

When DTC C15A2/62 is output, a short circuit inside the steering actuator or inside the steering control ECU is suspected.

Scheme 44

1. CHECK WIRE HARNESS Turn the engine switch off. Disconnect the connectors from the steering control ECU and the steering actuator. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Specified condition K69-1 (BMV) - K69-2 (BMU) 10 kohms or higher K69-1 (BMV) - K69-3 (BMW) 10 kohms or higher K69-2 (BMU) - K69-3 (BMW) 10 kohms or higher K69-1 (BMV) - Body ground 10 kohms or higher K69-2 (BMU) - Body ground 10 kohms or higher K69-3 (BMW) - Body ground 10 kohms or higher NG --> REPAIR OR REPLACE WIRE HARNESS OK: Go to next step
2. CHECK STEERING ACTUATOR Connect the connector to the steering actuator. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Specified condition K69-1 (BMV) - Body ground 10 kohms or higher K69-2 (BMU) - Body ground 10 kohms or higher K69-3 (BMW) - Body ground 10 kohms or higher NG --> REPLACE STEERING ACTUATOR OK --> REPLACE STEERING CONTROL ECU

HINT

The actuator only can be checked in this procedure. If it is normal, the steering control ECU is faulty.

Scheme 45

Scheme 46

1. CHECK WIRE HARNESS (POWER SOURCE CIRCUIT) Turn the engine switch off. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Specified condition A40-7 (PGND) - Body ground Below 1 ohms Turn the engine switch on (IG). Measure the voltage according to the value(s) in the table below. Voltage Tester connection Specified condition A40-8 (PIG) - Body ground 10 to 14 V NG --> REPAIR OR REPLACE WIRE HARNESS OK: Go to next step
2. CHECK WIRE HARNESS Turn the engine switch off. Disconnect the connectors from the steering control ECU and the steering actuator. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Specified condition K69-1 (BMV) - K69-2 (BMU) 10 kohms or higher K69-1 (BMV) - K69-3 (BMW) 10 kohms or higher K69-2 (BMU) - K69-3 (BMW) 10 kohms or higher K69-1 (BMV) - K26-5 (BMV+) Below 1 ohms K69-2 (BMU) - K26-4 (BMU+) Below 1 ohms K69-3 (BMW) - K26-13 (BMW+) Below 1 ohms K69-1 (BMV) - Body ground 10 kohms or higher K69-2 (BMU) - Body ground 10 kohms or higher K69-3 (BMW) - Body ground 10 kohms or higher NG --> REPAIR OR REPLACE WIRE HARNESS OK: Go to next step
3. CHECK STEERING ACTUATOR Connect the connector to the steering actuator. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Specified condition K69-1 (BMV) - K69-2 (BMU) Below 1 ohms K69-1 (BMV) - K69-3 (BMW) Below 1 ohms K69-2 (BMU) - K69-3 (BMW) Below 1 ohms K69-1 (BMV) - Body ground 10 kohms or higher K69-2 (BMU) - Body ground 10 kohms or higher K69-3 (BMW) - Body ground 10 kohms or higher NG --> REPLACE STEERING ACTUATOR OK: Go to next step
4. CHECK DTC Check for DTCs. Refer to «DTC CHECK / CLEAR»(ref-382810-S16608627522011012800000) . OK DTC C15A1/61 is not output. NG --> REPLACE STEERING ACTUATOR OK --> REPLACE STEERING CONTROL ECU

Scheme 47

1. CHECK STEERING CONTROL ECU Record and clear the DTCs. Refer to «DTC CHECK / CLEAR»(ref-382810-S16608627522011012800000) . Start the engine. Measure the voltage according to the value(s) in the table below. Voltage Tester connection Specified condition Proceed to A40-3 (IG) - A40-7 (PGND) 9 to 16 V A A40-3 (IG) - A40-7 (PGND) Below 9 V B A40-3 (IG) - A40-7 (PGND) Above 16 V C C --> CHECK AND REPAIR CHARGING SYSTEM B --> CHECK OR REPAIR HARNESS AND FUSE A: Go to next step
2. CHECK DTC Check for DTCs. Refer to «DTC CHECK / CLEAR»(ref-382810-S16608627522011012800000) . OK DTC C15C6/77 is not output. NG --> REPLACE STEERING CONTROL ECU OK --> END

Scheme 48

1. CHECK WIRE HARNESS (PGD2 - Body ground) Turn the engine switch off. Disconnect the negative (-) terminal cable from the battery. Disconnect the connector from the steering control ECU. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Condition Specified condition A40-7 (PGND) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE WIRE HARNESS OK: Go to next step
2. CHECK STEERING CONTROL ECU Connect the connector to the steering control ECU. Connect the negative (-) terminal cable to the battery. Record and clear the DTCs. Refer to «DTC CHECK / CLEAR»(ref-382810-S16608627522011012800000) . Start the engine. Measure the voltage according to the value(s) in the table below. Voltage Tester connection Specified condition Proceed to A40-8 (PIG) - A40-7 (PGND) 9 to 16 V A A40-8 (PIG) - A40-7 (PGND) Below 9 V B A40-8 (PIG) - A40-7 (PGND) Above 16 V C C --> CHECK OR REPAIR CHARGING SYSTEM B --> CHECK OR REPAIR HARNESS AND FUSE A: Go to next step
3. CHECK DTC Check for DTCs. Refer to «DTC CHECK / CLEAR»(ref-382810-S16608627522011012800000) . OK Neither DTC C15C7/78 nor C15C8/79 is output. NG --> REPLACE STEERING CONTROL ECU OK --> END

This problem may be caused by a malfunction in the electronically controlled brake or EPS system. Make sure that no DTC is output for the skid control ECU, power steering ECU, or steering control ECU before proceeding with the following procedures.

If a DTC is output for any of these ECUs, first troubleshoot it and then proceed.

HINT

This problem may be caused by a malfunction in the electronically controlled brake or EPS system.

Make sure that no DTC is output for the skid control ECU, power steering ECU, or steering control ECU before proceeding with the following procedures.

If a DTC is output for any of these ECUs, first troubleshoot it and then proceed.

Scheme 49

1. READ VALUE OF TECHSTREAM Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Check the record of continuous overheat preventive control. Enter the following menus: Chassis / VGRS / Data List. VGRS Tester Display Measurement Item/Range Normal Condition Motor Overheat Record Record of continuous overheat preventive control / Rec or Unrec Rec or Unrec Result A: "Rec" (Record motor overheating) B: "Unrec" (No record of motor overheating) HINT: If "Rec" is displayed, reset the setting to "Unrec". Refer to DATA LIST. B --> See step 3 A: Go to next step
2. CHECK HEAT PROTECTION FUNCTION FOR STEERING ACTUATOR Turn the engine switch on (IG) and wait for 30 minutes until the steering actuator cools down. Start the engine and slowly turn the steering wheel from lock to lock (approximately 90°/sec) 3 times. HINT: If turning the steering wheel quickly while driving at low speeds, the steering angle may differ between left and right, or the steering wheel may become off-center. However, this is not a malfunction. Check the number of turns from lock to lock. Result A: 2.7 turns B: 3.2 turns B --> See step 3 A --> VGRS SYSTEM IS NORMAL
3. CHECK STEERING EFFORT Start the engine. Turn the steering wheel. Check the steering effort. OK Below 6.5 N*m (66 kgf*cm, 57 in.*lbf) HINT: After completing the inspection or repair, attempt to simulate the problem and then perform step 1 again to reconfirm that the problem does not occur. NG --> GO TO POWER STEERING SYSTEM OK: Go to next step
4. CHECK STEERING ACTUATOR Check for an abnormal noise or vibration in the steering actuator. OK Neither an abnormal noise or vibration occurs. NG --> GO TO STEERING WHEEL VIBRATES OR ABNORMAL NOISE IS HEARD FROM STEERING WHEEL OK: Go to next step
5. CHECK WIRE HARNESS Turn the engine switch on (IG). Measure the voltage and resistance according to the value(s) in the table below. Voltage Tester connection Condition Specified condition A40-3 (IG) - Body ground Engine switch on (IG) 10 to 14 V A40-8 (PIG) - Body ground Engine switch on (IG) 10 to 14 V Turn the engine switch off. Measure the resistance according to the value(s) in the table below. Resistance Tester connection Condition Specified condition A40-7 (PGND) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE WIRE HARNESS OK --> REPLACE STEERING CONTROL ECU

HINT

1. Check that the steering wheel is centered.
2. After checking that no DTC is output for the VGRS system, perform the following procedure.

HINT

Check that no DTC is output for the VGRS system, electronically controlled brake system, and ABS system.

HINT

Check that there is no problem in CAN and BEAN communications before performing the following procedure.

If there is any problem in these communications, first troubleshoot it and then proceed.