Electric Steering Lock (Diagnostics): Overview Lexus GS III facelift

SYSTEM DESCRIPTION

1. DESCRIPTION The steering lock system locks/unlocks the steering lock by activating the steering lock bar with a motor. The steering lock ECU activates the motor based on signals from the certification ECU and power source control ECU assembly.
2. FUNCTIONS OF COMPONENTS The steering lock ECU controls the system based on information from the following components. Item Function Steering lock actuator assembly Consists of a motor, lock bar, lock/unlock position sensors, etc. Activated by the steering lock ECU. Steering lock ECU Included in the steering lock actuator assembly. Activates the steering lock motor based on permission signals from the power source control ECU and certification ECU. Detects steering lock/unlock positions and transmits the status to other ECUs. Power source control ECU assembly Permits the steering lock ECU to supply power to activate the motor. The power source control ECU and certification ECU permit engine start after receiving an unlock signal from the steering lock ECU. Certification ECU Orders the steering lock ECU to lock/unlock the steering lock. The power source control ECU and certification ECU permit engine start after receiving an unlock signal from the steering lock ECU. IG2 relay Controlled by the power source control ECU. Sends IG signals to the steering lock ECU.

DESCRIPTION

If the steering lock ECU determines that there is a malfunction inside the ECU, it outputs this DTC. Diagnostic communication between the steering lock ECU and the Techstream is performed via the certification ECU as the steering lock ECU is not connected to the BEAN.

The power source control ECU controls the power supply to activate the steering lock motor. This prevents the steering from being locked while the vehicle is moving.

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1. INSPECT STEERING LOCK ACTUATOR ASSEMBLY Measure the voltage according to the value(s) in the table below. Voltage Tester connection (Symbols) Condition Specified condition K28-3 (IGE) - K28-2 (SGND) Engine switch off Turn the engine switch on (ACC or IG) Motor active: Below 1 V Motor not active: 10 to 12 V K28-3 (IGE) - K28-2 (SGND) Adjust the shift lever to the P position Turn the engine switch off Open the driver's door Motor active: Below 1 V Motor not active: 10 to 12 V HINT: The steering lock ECU and steering lock actuator assembly are supplied as a unit. OK --> REPLACE STEERING LOCK ACTUATOR ASSEMBLY NG: Go to next step
2. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BODY GROUND) Disconnect the K28 connector from the steering lock actuator assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-2 (SGND) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - POWER SOURCE CONTROL ECU) Disconnect the K73 connector from the power source control ECU assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-3 (IGE) - K73-32 (SLR+) Always Below 1 ohms K28-3 (IGE) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE POWER SOURCE CONTROL ECU ASSEMBLY

The steering lock ECU receives IG2 relay signals. Receiving the signals, the steering lock ECU determines that the vehicle is moving. The steering lock ECU does not lock the steering when it receives an IG2 relay ON signal (to prevent the steering from being locked while the vehicle is moving).

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1. INSPECT IGNITION RELAY NO. 2 Remove the IG2 relay from the engine room R/B No. 2. 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 IGNITION RELAY NO. 2 OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BODY GROUND) Disconnect the K28 connector from the steering lock actuator assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-1 (GND) - Body ground Always Below 1 ohms K28-2 (SGND) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BATTERY) Measure the voltage according to the value(s) in the table below. Voltage Tester connection (Symbols) Condition Specified condition K28-6 (IG2) - K28-1 (GND) Engine switch on (IG) 10 to 14 V K28-6 (IG2) - K28-2 (SGND) Engine switch on (IG) 10 to 14 V Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition *K28-6 (IG2) - K28-7 (B) Engine switch off 10 kohms higher *: This measurement is performed with the engine switch off to check for a battery voltage short in the IG2 circuit. OK --> REPLACE STEERING LOCK ACTUATOR ASSEMBLY NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BATTERY)

The steering lock ECU is connected to the power source control ECU assembly and certification ECU. The steering lock ECU cannot activate the motor unless it obtains permission from both the ECUs. (The power source control ECU assembly permits the steering lock ECU to supply power to activate the motor.)

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1. CHECK VEHICLE CONDITION Check the problem symptom of the steering lock system. Result Condition Proceed to Steering lock cannot be released A Steering cannot be locked B B --> See step 6 A: Go to next step
2. READ VALUE OF TECHSTREAM Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Read the Data List. Enter the following menus: Body / Smart Access / Data List. SMART ACCESS Tester Display Measurement Item/Range Normal Condition Lock/Unlock Receive Steering lock command reception record/YES or NO YES: Steering lock/unlock signal received NO: Steering lock/unlock signal not received Check if steering unlock command reception is confirmed. OK "YES" is displayed on the Techstream display. NG --> CHECK SMART ACCESS SYSTEM WITH PUSH-BUTTON START OK: Go to next step
3. INSPECT STEERING LOCK ACTUATOR ASSEMBLY Measure the voltage according to the value(s) in the table below. Voltage Tester connection (Symbols) Condition Specified condition K28-3 (IGE) - K28-2 (SGND) Engine switch off Turn the engine switch on (ACC or IG) Motor active: Below 1 V Motor not active: 10 to 12 V OK --> PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE NG: Go to next step
4. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BODY GROUND) Disconnect the K28 connector from the steering lock actuator assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-2 (SGND) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
5. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - POWER SOURCE CONTROL ECU) Disconnect the K73 connector from the power source control ECU assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-3 (IGE) - K73-32 (SLR+) Always Below 1 ohms K28-3 (IGE) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE POWER SOURCE CONTROL ECU ASSEMBLY
6. INSPECT STEERING LOCK ACTUATOR ASSEMBLY Measure the voltage according to the value(s) in the table below. Voltage Tester connection (Symbols) Condition Specified condition K28-3 (IGE) - K28-2 (SGND) Adjust the shift lever to the P position Turn the engine switch off Open the driver's door Motor active: Below 1 V Motor not active: 10 to 12 V OK --> PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE NG: Go to next step
7. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - POWER SOURCE CONTROL ECU) Disconnect the K28 connector from the steering lock actuator assembly. Disconnect the K73 connector from the power source control ECU assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-3 (IGE) - K73-32 (SLR+) Always Below 1 ohms K28-3 (IGE) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE POWER SOURCE CONTROL ECU ASSEMBLY

The unlock position sensor is one of the components comprising the steering lock actuator. The sensor switch contact closes when the steering lock is released. The steering lock release signal is then sent to the power source control ECU assembly. Receiving the signal, the ECU permits engine start. (This prevents the engine from being started with the steering locked.)

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1. INSPECT STEERING LOCK ACTUATOR ASSEMBLY Measure the voltage according to the value(s) in the table below. Voltage Tester connection (Symbols) Condition Specified condition K28-4 (SLP1) - K28-2 (SGND) Engine switch off Turn the engine switch on (ACC or IG) Below 1 V OK --> CHECK PUSH BUTTON START FUNCTION NG: Go to next step
2. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - POWER SOURCE CONTROL ECU) Disconnect the K28 connector from the steering lock actuator assembly. Disconnect the K73 connector from the power source control ECU assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-4 (SLP1) - K73-26 (SLP) Always Below 1 ohms K28-4 (SLP1) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE STEERING LOCK ACTUATOR ASSEMBLY

This circuit supplies power source voltage from the battery to terminal B of the steering lock ECU. This is used as power source for the CPU, motor, communication, and peripheral circuits.

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1. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BODY GROUND) Disconnect the K28 connector from the steering lock actuator assembly. Measure the resistance according to the value(s) in the table below. Resistance Tester connection (Symbols) Condition Specified condition K28-1 (GND) - Body ground Always Below 1 ohms K28-2 (SGND) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BATTERY) Measure the voltage according to the value(s) in the table below. Voltage Tester connection (Symbols) Condition Specified condition K28-7 (B) - K28-1 (GND) Always 10 to 14 V K28-7 (B) - K28-2 (SGND) Always 10 to 14 V OK --> PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (STEERING LOCK ACTUATOR ASSEMBLY - BATTERY)