Lexus NX: Unable to Unlock Steering Wheel (Hybrid Control System cannot Start)

Lexus NX Service Manual / Steering / Steering Column / Steering Lock System / Unable to Unlock Steering Wheel (Hybrid Control System cannot Start)

DESCRIPTION

The steering lock actuator assembly activates the steering lock motor and moves the lock bar into the steering column to lock the steering.

The steering may not unlock when the lock bar gets stuck in the lock hole of the steering column. In this case, if the power switch is turned on (IG) while shaking the steering wheel, as is done for a vehicle with a mechanical key, the lock bar will be unlocked. If the certification ECU (smart key ECU assembly), ID code box (immobiliser code ECU) or ECM is replaced, the system needs to be initialized. Otherwise, the steering cannot be unlocked and the hybrid control system cannot be started.

Related Data List and Active Test Items

Problem Symptom	Data List Item	Active Test Item
Unable to unlock steering wheel (Hybrid control system cannot start)	Smart Access Unlock Request Receive S Code Check L Code Check Steering Unlock	-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the power switch off, connect the Techstream to the vehicle and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Access. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.
Perform either of the following operations to lock/unlock the steering:
- To unlock the steering, carry the key and turn the power switch on (ACC) or on (IG) with the shift lever in P.
- To lock the steering, turn the power switch off with the shift lever in P, and then open a door.
The steering lock system uses LIN communication. First perform the inspections in "How to Proceed with Troubleshooting" to confirm that there are no communication malfunctions before proceeding with troubleshooting.
Click here
After performing repairs, confirm that the problem does not recur.
Make sure that no DTCs are output. If any DTCs are output, proceed to the Diagnostic Trouble Code Chart.
Click here
Inspect the fuses for circuits related to this system before performing the following procedure.
When replacing the steering lock ECU (steering lock actuator assembly), certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU), registration must be performed.
Click here
If the steering lock ECU (steering lock actuator assembly) is replaced, be sure to confirm that the steering is unlocked by turning the steering wheel to the left and right before starting the hybrid control system. This function prevents the hybrid control system from starting while the steering is locked. If the steering is locked for any reason, open and close a door with the power switch off, and then unlock the steering by pressing the power switch.
After the power switch is turned off, there may be a waiting time before disconnecting the negative (-) auxiliary battery terminal.
Click here
When disconnecting and reconnecting the auxiliary battery
Click here

HINT:

When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

Click here

PROCEDURE

1.	CHECK POWER SWITCH (SWITCH CONDITION)

(a) Check the power source mode change.

(1) When the key is inside the vehicle and the shift lever is in P, check that pressing the power switch with the brake pedal released causes the power source mode to change as follows:

OK:

Off → On (ACC) → On (IG) → Off

GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function) (PROBLEM SYMPTOMS TABLE)

2.	CHECK INDICATOR

(a) With the power switch on (IG), check that Steering Lock active is displayed on the multi-information display in the combination meter assembly.

Result	Proceed to
Steering Lock active is displayed.	A
Steering Lock active is not displayed.	B

GO TO STEP 4

3.	CHECK STEERING UNLOCK

(a) While turning the steering wheel left and right, press the power switch.

(b) Check that the steering is unlocked.

Result	Proceed to
The steering is unlocked.	A
The steering is not unlocked.	B

END

4.	CHECK FOR DTC

(a) Using the Techstream, check if the certification ECU (smart key ECU assembly) DTC is output.

Body Electrical > Smart Access > Trouble Codes Body Electrical > Power Source Control > Trouble Codes

Result	Proceed to
DTCs are not output.	A
DTCs are output.	B

GO TO DIAGNOSTIC PROCEDURE INDICATED BY OUTPUT DTC

5.	READ VALUE USING TECHSTREAM (UNLOCK REQUEST RECEIVE)

(a) Use the Data List to check if the steering lock request is functioning properly.

Body Electrical > Smart Access > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Unlock Request Receive	Unlock request signal received state	OK or NG	OK: Unlock request signal received within 10 seconds of power switch on (IG) or on (ACC), or of a hybrid control system start operation being performed NG: Power switch not turned on (IG) or on (ACC), and hybrid control system start operation not performed	The hybrid control system cannot be started when an unlock request signal cannot be received. If OK is not displayed even though the steering unlock conditions are met, the certification ECU (smart key ECU assembly) may be malfunctioning.

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Unlock Request Receive

Unlock request signal received state

OK or NG

OK: Unlock request signal received within 10 seconds of power switch on (IG) or on (ACC), or of a hybrid control system start operation being performed

NG: Power switch not turned on (IG) or on (ACC), and hybrid control system start operation not performed

The hybrid control system cannot be started when an unlock request signal cannot be received.
If OK is not displayed even though the steering unlock conditions are met, the certification ECU (smart key ECU assembly) may be malfunctioning.

Body Electrical > Smart Access > Data List

Tester Display
Unlock Request Receive

OK:

Within 10 seconds of turning the power switch on (ACC) or on (IG) or starting the hybrid control system, the Data List item changes to "OK".

GO TO STEP 15

6.	READ VALUE USING TECHSTREAM (S CODE CHECK)

(a) Use the Data List to check if S code certification is functioning properly.

Body Electrical > Smart Access > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
S Code Check	Verification result between certification ECU (smart key ECU assembly) and ID code box (immobiliser code ECU)	OK or NG	OK: Verification result normal NG: Verification result abnormal	When NG is displayed: The ID code for the certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU) is not registered, or the certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU) is malfunctioning. The steering cannot be locked. The steering cannot be unlocked (the hybrid control system cannot be started).

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

S Code Check

Verification result between certification ECU (smart key ECU assembly) and ID code box (immobiliser code ECU)

OK or NG

OK: Verification result normal

NG: Verification result abnormal

When NG is displayed:

The ID code for the certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU) is not registered, or the certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU) is malfunctioning.
The steering cannot be locked.
The steering cannot be unlocked (the hybrid control system cannot be started).

Body Electrical > Smart Access > Data List

Tester Display
S Code Check

OK:

OK is displayed on the Techstream.

HINT:

Reasons for verification failure:

The certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU) is malfunctioning.
There is a problem with the communication between ECUs.
An ECU is replaced, but is not registered.
An ECU is replaced with an ECU which has a code already stored in it.

GO TO STEP 14

7.	READ VALUE USING TECHSTREAM (L CODE CHECK)

(a) Use the Data List to check if L code certification is functioning properly.

Body Electrical > Smart Access > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
L Code Check	Verification result between ID code box (immobiliser code ECU) and steering lock ECU (steering lock actuator assembly)	OK or NG	OK: Verification result normal NG: Verification result abnormal	When NG is displayed: The ID code for the ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator assembly) is not registered, or the ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator assembly) is malfunctioning. The steering cannot be locked. The steering cannot be unlocked (the hybrid control system cannot be started).

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

L Code Check

Verification result between ID code box (immobiliser code ECU) and steering lock ECU (steering lock actuator assembly)

OK or NG

OK: Verification result normal

NG: Verification result abnormal

When NG is displayed:

The ID code for the ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator assembly) is not registered, or the ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator assembly) is malfunctioning.
The steering cannot be locked.
The steering cannot be unlocked (the hybrid control system cannot be started).

Body Electrical > Smart Access > Data List

Tester Display
L Code Check

OK:

OK is displayed on the Techstream.

HINT:

Reasons for verification failure:

The steering lock ECU (steering lock actuator assembly) or ID code box (immobiliser code ECU) is malfunctioning.
There is a problem with the communication between ECUs.
An ECU is replaced, but is not registered.
An ECU is replaced with an ECU which has a code already stored in it.

GO TO STEP 11

8.	INSPECT STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

(a) Measure the resistance and voltage according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
I2-1 (GND) - Body ground	Always	Below 1 Ω

NOTICE:

If the result is not as specified, check for looseness in the ground cable connection.

Standard Voltage:

Tester Connection	Condition	Specified Condition
I2-7 (B) - Body ground	Always	11 to 14 V

*a	Component with harness connected (Steering Lock ECU (Steering Lock Actuator Assembly))

REPAIR OR REPLACE HARNESS OR CONNECTOR

9.	CHECK HARNESS AND CONNECTOR (GROUND)

(a) Disconnect the I2 steering lock ECU (steering lock actuator assembly) connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
I2-1 (GND) - Body ground	Always	Below 1 Ω

*a	Front view of wire harness connector (to Steering Lock ECU (Steering Lock Actuator Assembly))

REPAIR OR REPLACE HARNESS OR CONNECTOR

10.	INSPECT STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

(a) Reconnect the I2 steering lock ECU (steering lock actuator assembly) connector.

(b) Check the signal waveform according to the condition(s) in the table below.

Standard Frequency:

Item	Content
Tester Connection	I2-3 (IGE) - I2-1 (GND)
Tool Setting	2 V/DIV., 200 ms./DIV.
Vehicle Condition	Steering lock motor not operating → Operating → Not operating

HINT:

When taking measurements when the lock motor is stopped, it is not necessary to perform any operations.
In order to take measurements when the lock motor is operating, perform either of the following operations:
- To unlock the steering, carry the key and turn the power switch on (ACC) or on (IG).
- To lock the steering, turn the power switch off with the shift lever in P, and then open a door.

Component with harness connected

(Steering Lock ECU (Steering Lock Actuator Assembly))

Steering Lock Motor not Operating

Steering Lock Motor Operating

Result	Proceed to
OK (for Manual tilt and manual telescopic steering column)	A
OK (for Power tilt and power telescopic steering column)	B
NG	C

REPLACE STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

GO TO STEP 12

11.	REPLACE STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

(a) Replace the steering lock ECU (steering lock actuator assembly) with a new one.

for Manual tilt and manual telescopic steering column: Click here

(b) Replace the steering lock ECU (steering lock actuator assembly) with a new one.

for Power tilt and power telescopic steering column: Click here

Click here

(d) Turn the power switch on (IG).

(e) Use the Data List to check if L code certification is functioning properly again.

Body Electrical > Smart Access > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

L Code Check

Verification result between ID code box (immobiliser code ECU) and steering lock ECU (steering lock actuator assembly)

OK or NG

OK: Verification result normal

NG: Verification result abnormal

When NG is displayed:

The ID code for the ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator assembly) is not registered, or the ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator assembly) is malfunctioning.
The steering cannot be locked.
The steering cannot be unlocked (the hybrid control system cannot be started).

Body Electrical > Smart Access > Data List

Tester Display
L Code Check

OK:

OK is displayed on the Techstream.

END

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

12.	CHECK HARNESS AND CONNECTOR (STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY) - CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

(b) Disconnect the I2 steering lock ECU (steering lock actuator assembly) connector.

(d) Check for deformation and corrosion of the connector case and terminals.

OK:

There is no deformation or corrosion of the connector case or terminals.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
I2-3 (IGE) - I53-24 (SLR+)	Always	Below 1 Ω
I2-3 (IGE) or I53-24 (SLR+) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

13.	INSPECT STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

(a) Reconnect the I2 steering lock ECU (steering lock actuator assembly) connector.

(b) Reconnect the I53 certification ECU (smart key ECU assembly) connector.

Standard Voltage:

Tester Connection	Condition	Specified Condition
I2-3 (IGE) - Body ground	Always	11 to 14 V

*a	Component with harness connected (Steering Lock ECU (Steering Lock Actuator Assembly))

Result	Proceed to
OK	A
NG (for Manual tilt and manual telescopic steering column)	B
NG (for Power tilt and power telescopic steering column)	C

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPLACE STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

14.	REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Replace the certification ECU (smart key ECU assembly) with a new one.

Click here

(b) Perform registration procedures.

Click here

Body Electrical > Smart Access > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

S Code Check

Verification result between certification ECU (smart key ECU assembly) and ID code box (immobiliser code ECU)

OK or NG

OK: Verification result normal

NG: Verification result abnormal

When NG is displayed:

The ID code for the certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU) is not registered, or the certification ECU (smart key ECU assembly) or ID code box (immobiliser code ECU) is malfunctioning.
The steering cannot be locked.
The steering cannot be unlocked (the hybrid control system cannot be started).

Body Electrical > Smart Access > Data List

Tester Display
S Code Check

OK:

OK is displayed on the Techstream.

END

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

15.	INSPECT STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
I2-4 (SLP1) - Body ground	Always	11 to 14 V

*a	Component with harness connected (Steering Lock ECU (Steering Lock Actuator Assembly))

GO TO STEP 18

16.	READ VALUE USING TECHSTREAM (STEERING UNLOCK)

(a) Check that the steering is locked.

(b) Read the Data List according to the display on the Techstream.

Body Electrical > Smart Access > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Steering Unlock

Steering lock ECU (steering lock actuator assembly) unlock confirmation status

Unset or Set

Unset: Unlock not confirmed

Set: Unlock confirmed

When Unset is displayed, the steering is not unlocked (the hybrid control system cannot be started).

Body Electrical > Smart Access > Data List

Tester Display
Steering Unlock

OK:

"Set" is displayed on the Techstream.

Result	Proceed to
OK	A
NG (for Manual tilt and manual telescopic steering column)	B
NG (for Power tilt and power telescopic steering column)	C

REPLACE STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

17.	READ VALUE USING TECHSTREAM (UNLOCK REQUEST RECEIVE)

(a) Replace the certification ECU (smart key ECU assembly) with a new one.

Click here

(b) Perform registration procedures.

Click here

(d) Use the Data List to check if the steering lock request is functioning properly.

Body Electrical > Smart Access > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Unlock Request Receive

Unlock request signal received state

OK or NG

OK: Unlock request signal received within 10 seconds of power switch on (IG) or on (ACC), or of a hybrid control system start operation being performed

NG: Power switch not turned on (IG) or on (ACC), and hybrid control system start operation not performed

The hybrid control system cannot be started when an unlock request signal cannot be received.
If OK is not displayed even though the steering unlock conditions are met, the certification ECU (smart key ECU assembly) may be malfunctioning.

Body Electrical > Smart Access > Data List

Tester Display
Unlock Request Receive

OK:

Within 10 seconds of turning the power switch on (ACC) or on (IG) or starting the hybrid control system, the Data List item changes to "OK".

END

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

18.	CHECK HARNESS AND CONNECTOR (STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY) - CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

(b) Disconnect the I2 steering lock ECU (steering lock actuator assembly) connector.

(d) Check for deformation and corrosion of the connector case and terminals.

OK:

There is no deformation or corrosion of the connector case or terminals.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
I2-4 (SLP1) - I53-23 (SLP)	Always	Below 1 Ω
I2-4 (SLP1) or I53-23 (SLP) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

19.	READ VALUE USING TECHSTREAM (UNLOCK REQUEST RECEIVE)

(a) Replace the steering lock ECU (steering lock actuator assembly) with a new one.

for Manual tilt and manual telescopic steering column: Click here

(b) Replace the steering lock ECU (steering lock actuator assembly) with a new one.

for Power tilt and power telescopic steering column: Click here

Click here

(d) Turn the power switch on (IG).

(e) Use the Data List to check if the steering lock request is functioning properly.

Body Electrical > Smart Access > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Unlock Request Receive

Unlock request signal received state

OK or NG

OK: Unlock request signal received within 10 seconds of power switch on (IG) or on (ACC), or of a hybrid control system start operation being performed

NG: Power switch not turned on (IG) or on (ACC), and hybrid control system start operation not performed

The hybrid control system cannot be started when an unlock request signal cannot be received.
If OK is not displayed even though the steering unlock conditions are met, the certification ECU (smart key ECU assembly) may be malfunctioning.

Body Electrical > Smart Access > Data List

Tester Display
Unlock Request Receive

OK:

Within 10 seconds of turning the power switch on (ACC) or on (IG) or starting the hybrid control system, the Data List item changes to "OK".

END

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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Lexus NX: Unable to Unlock Steering Wheel (Hybrid Control System cannot Start)

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