Lexus NX: Power Source Mode does not Change to ON (READY)

Lexus NX Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Start Function) / Power Source Mode does not Change to ON (READY)

DESCRIPTION

When the electrical key transmitter sub-assembly is in the cabin and the power switch is pressed, the certification ECU (smart key ECU assembly) receives a signal and changes the power source mode. In addition, when the power switch is pressed with the shift lever in P and the brake pedal depressed, the hybrid control system turns on (READY).

Related Data List and Active Test Items

Problem Symptom	Data List and Active Test
Power source mode does not change to ON (READY)	Power Source Control Stop Light Switch1 Steering Unlock Switch Shift P Signal IG Relay Monitor (Inside) IG Relay Monitor (Outside) Latch Circuit Starter Request Signal Power Supply Condition Smart Access Immobiliser Engine Start Request S Code Check L Code Check

WIRING DIAGRAM

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CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the power switch off, connect the Techstream to the DLC3 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.
The smart access system with push-button start (for Start Function) uses the LIN communication system and CAN communication system. Inspect the communication function by following How to Proceed with Troubleshooting. Troubleshoot the smart access system with push-button start (for Start Function) after confirming that the communication systems are functioning properly.
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If the smart access system with push-button start (for Start Function) has been canceled, enable the system before performing troubleshooting.
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Inspect the fuses of circuits related to this system before performing the following procedure.
Before replacing the certification ECU (smart key ECU assembly) or electrical key transmitter sub-assembly, refer to smart access system with push-button start (for Start Function) Precaution.
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After completing repairs, confirm that the problem does not recur.

HINT:

When the cable is disconnected and reconnected to the negative (-) auxiliary battery terminal, the power source mode returns to the state it was in before the cable was disconnected.
If the power source mode is changed from on (IG) to on (ACC) with the shift lever in any position other than P, then the shift lever is moved to P and the power switch is pressed with the brake pedal depressed, the power source mode will changed off.

PROCEDURE

1.	CHECK ELECTRICAL KEY TRANSMITTER SUB-ASSEMBLY

(a) Press a switch of the electrical key transmitter sub-assembly.

OK:

The electrical key transmitter sub-assembly LED illuminates.

GO TO STEP 11

2.	READ VALUE USING TECHSTREAM (KEY LOW BATTERY)

(a) Connect the Techstream to the DLC3.

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

(d) Enter the following menus: Body Electrical / Smart Access / Data List.

(e) 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
Key Low Battery	Transmitter battery depleted	No or Yes	No: Transmitter battery not depleted Yes: Transmitter battery depleted	The electrical key transmitter sub-assembly sends voltage information to the certification ECU (smart key ECU assembly) when it is transmitting. The certification ECU (smart key ECU assembly) displays "Yes" for the "Key Low Battery" item of the Data List when this voltage information indicates 2.2 V or less. This Data List item should be checked when the electrical key transmitter sub-assembly is at room temperature (example: at -20°C (-4°F), "Yes" may be displayed even if the transmitter battery is new).

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Key Low Battery

Transmitter battery depleted

No or Yes

No: Transmitter battery not depleted

Yes: Transmitter battery depleted

The electrical key transmitter sub-assembly sends voltage information to the certification ECU (smart key ECU assembly) when it is transmitting. The certification ECU (smart key ECU assembly) displays "Yes" for the "Key Low Battery" item of the Data List when this voltage information indicates 2.2 V or less. This Data List item should be checked when the electrical key transmitter sub-assembly is at room temperature (example: at -20°C (-4°F), "Yes" may be displayed even if the transmitter battery is new).

Body Electrical > Smart Access > Data List

Tester Display
Key Low Battery

OK:

"No" is displayed on the Techstream screen.

REPLACE TRANSMITTER BATTERY

3.	CHECK WAVE ENVIRONMENT

(a) If the problem occurs in certain locations or times of day, the possibility of wave interference is high.

HINT:

Whether the problem is due to wave interference can be checked by holding the electrical key transmitter sub-assembly near the door control receiver.

OK:

Power source mode changes to on (READY).

AFFECTED BY WAVE INTERFERENCE

4.	CHECK POWER SWITCH CONDITION

(a) Get into the vehicle while carrying an electrical key transmitter sub-assembly.

(b) Move the shift lever to P.

Result	Proceed to
Power source mode changes : Off → on (ACC) → on (IG) → off	A
Power source mode does not change to on (ACC) or on (IG)	B
Power source mode changes to on (IG) but not to on (ACC)	C
Power source mode changes to on (ACC) but not to on (IG)	D

GO TO POWER SOURCE MODE DOES NOT CHANGE TO ON (IG AND ACC)

GO TO POWER SOURCE MODE DOES NOT CHANGE TO ON (ACC)

GO TO POWER SOURCE MODE DOES NOT CHANGE TO ON (IG)

5.	READ VALUE USING TECHSTREAM (SHIFT P SIGNAL)

(a) Connect the Techstream to the DLC3.

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

(d) Enter the following menus: Body Electrical / Power Source Control / Data List.

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

Body Electrical > Power Source Control > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Shift P Signal	Shift position P	OFF or ON	OFF: Shift lever not in P ON: Shift lever in P	Use this item to determine whether the shift lever position switch (P) is malfunctioning.

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Shift P Signal

Shift position P

OFF or ON

OFF: Shift lever not in P

ON: Shift lever in P

Use this item to determine whether the shift lever position switch (P) is malfunctioning.

Body Electrical > Power Source Control > Data List

Tester Display
Shift P Signal

OK:

The item in the Data List changes according to the shift position.

GO TO HYBRID CONTROL SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

6.	CHECK FOR DTC

(a) Using the Techstream, check for DTCs.

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

Result	Proceed to
DTCs are not output	A
Smart access system with push-button start (for Start Function) DTCs are output	B

GO TO DIAGNOSTIC TROUBLE CODE CHART

7.	READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH1)

(a) Connect the Techstream to the DLC3.

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

(d) Enter the following menus: Body Electrical / Power Source Control / Data List.

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

Body Electrical > Power Source Control > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Stop Light Switch1	State of brake pedal	OFF or ON	OFF: Brake pedal released ON: Brake pedal depressed	Use this item to determine whether the stop light switch is malfunctioning. The hybrid control system cannot be started when this item is OFF. If the stop light switch is malfunctioning, the hybrid control system can be started by pressing and holding the power switch for a certain period of time.

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Stop Light Switch1

State of brake pedal

OFF or ON

OFF: Brake pedal released

ON: Brake pedal depressed

Use this item to determine whether the stop light switch is malfunctioning.
The hybrid control system cannot be started when this item is OFF.
If the stop light switch is malfunctioning, the hybrid control system can be started by pressing and holding the power switch for a certain period of time.

Body Electrical > Power Source Control > Data List

Tester Display
Stop Light Switch1

OK:

The Techstream display changes correctly in response to the brake operation.

GO TO STEP 12

8.	READ VALUE USING TECHSTREAM (STARTER REQUEST SIGNAL)

(a) Connect the Techstream to the DLC3.

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

(d) Enter the following menus: Body Electrical / Power Source Control / Data List.

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

Body Electrical > Power Source Control > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Starter Request Signal	Hybrid control system start request signal status	OFF or ON	OFF: After approx. 1 second has elapsed, the power switch is released ON: With the shift lever in P and brake pedal depressed, the power switch is pressed and held	When the hybrid control system cannot be started due to a start request signal malfunction, OFF is displayed. When the power switch is pressed, the duration of time that ON is displayed will be extremely short. As such, the power switch needs to be pressed and held for a certain period of time.

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Starter Request Signal

Hybrid control system start request signal status

OFF or ON

OFF: After approx. 1 second has elapsed, the power switch is released

ON: With the shift lever in P and brake pedal depressed, the power switch is pressed and held

When the hybrid control system cannot be started due to a start request signal malfunction, OFF is displayed.
When the power switch is pressed, the duration of time that ON is displayed will be extremely short. As such, the power switch needs to be pressed and held for a certain period of time.

Body Electrical > Power Source Control > Data List

Tester Display
Starter Request Signal

NOTICE:

Check that the smart warning light is displayed on the multi-information display in the combination meter assembly, and then press the power switch.

OK:

The Techstream display changes correctly in response to the power switch operation.

GO TO HYBRID CONTROL SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

9.	CHECK STEERING LOCK

(a) Check that the steering unlocks when the power switch is turned on (ACC).

OK:

The steering unlocks.

GO TO STEERING LOCK SYSTEM (UNABLE TO UNLOCK STEERING)

10.	CHECK SECURITY INDICATOR LIGHT (IMMOBILISER SYSTEM UNSET)

(a) Get into the vehicle while carrying an electrical key transmitter sub-assembly.

(b) Move the shift lever to P.

(c) Press the power switch with the brake pedal released and check that the security indicator light changes from blinking to off at the same time that the power source mode changes to on (ACC).

HINT:

The immobiliser function can be determined to be operating correctly if the security indicator light changes from blinking to off at the same time that the power source mode changes to on (ACC).

OK:

The security indicator light changes from blinking to off at the same time that the power source mode changes to on (ACC).

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

GO TO IMMOBILISER SYSTEM (PROBLEM SYMPTOMS TABLE)

11.	INSPECT TRANSMITTER BATTERY

(a) Inspect the transmitter battery.

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NOTICE:

Do not wrap the lead wire around a terminal, wedge it between terminals, or solder it. The terminal may be deformed or damaged, and the transmitter battery will not be able to be installed correctly.

REPLACE ELECTRICAL KEY TRANSMITTER SUB-ASSEMBLY

REPLACE TRANSMITTER BATTERY

12.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - STOP LIGHT SWITCH ASSEMBLY)

(a) Disconnect the I51 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the A1 stop light switch assembly connector.

Standard Voltage:

Tester Connection	Condition	Specified Condition
A1-1 (B) - Body ground	Power switch off	11 to 14 V

*a	Front view of wire harness connector (to Stop Light Switch Assembly)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
I51-2 (STP1) - A1-2 (L)	Always	Below 1 Ω
I51-2 (STP1) or A1-2 (L) - Body ground	Always	10 kΩ or higher
A1-3 (GND) - Body ground	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

13.	INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Inspect the stop light switch assembly.

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REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPLACE STOP LIGHT SWITCH ASSEMBLY

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Lexus NX: Power Source Mode does not Change to ON (READY)

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Theft Deterrent System

Precaution

Parts Location

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