Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Engine does not Start

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Start Function) / Engine does not Start

DESCRIPTION

When the electrical key transmitter sub-assembly is in the cabin and the engine switch is pressed, the certification ECU (smart key ECU assembly) receives a signal and changes the power source mode. Additionally, when the shift lever is in P and the brake pedal is depressed, the engine can be started by pressing the engine switch. If the steering is unlocked, the engine can also be started by pressing the engine switch with the shift lever in N and the brake pedal depressed.

Related Data List and Active Test Items

Problem Symptom

Data List and Active Test

Engine does not start
Power Source Control
  • Stop Light Switch1
  • Steering Unlock Switch
  • Shift P Signal
  • Neutral SW/ Clutch SW
  • 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
Starting Control
  • Starter SW
  • Shift Position P or N
  • Ignition

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When using the Techstream with the engine 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.

    Click here

  • If the smart access system with push-button start (for Start Function) has been canceled, enable the system before performing troubleshooting.

    Click here

  • Inspect the fuses of circuits related to this system before performing the following procedure.
  • Before replacing the certification ECU (smart key ECU assembly) or an electrical key transmitter sub-assembly, refer to smart access system with push-button start (for Start Function) Precaution.

    Click here

  • After completing repairs, confirm that the problem does not recur.

HINT:

  • When the cable is disconnected and reconnected to the negative (-) battery terminal, the power source mode returns to the state it was in before the cable was disconnected.
  • If the engine switch is turned from on (IG) to on (ACC) with the shift lever in any position other than P, and then the shift lever is moved to P and the engine switch is pressed with the brake pedal depressed, the engine switch will turn off.
  • If the brake pedal is repeatedly depressed while the engine is stopped, the brake booster pressure will be released and the force required to depress the brake pedal to illuminate the stop lights will increase.

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.

NG

GO TO STEP 19

OK

2.

READ VALUE USING TECHSTREAM (KEY LOW BATTERY)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(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. "Yes" is displayed for the Data List item "Key Low Battery" 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

Result

Proceed to

"No" is displayed on the Techstream screen

A

"Yes" is displayed on the Techstream screen

B
B

REPLACE TRANSMITTER BATTERY

A

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:

Engine starts.

OK

AFFECTED BY WAVE INTERFERENCE
NG

4.

CHECK ENGINE SWITCH CONDITION

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

(b) Move the shift lever to P.

(c) With the brake pedal released, check that pressing the engine switch causes the power source mode to change.

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
B

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

C

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

D

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

A

5.

READ VALUE USING TECHSTREAM (NEUTRAL SW/ CLUTCH SW, SHIFT POSITION P OR N)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Power Source Control or Starting 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

Neutral SW/ Clutch SW

Shift position (P and N)

OFF or ON

OFF: Shift lever in any position other than P or N

ON: Shift lever in P or N
  • Use this item to determine if the park/neutral position switch assembly is malfunctioning.
  • When the engine cannot be started due to a park/neutral position switch assembly malfunction, OFF is displayed.
Body Electrical > Power Source Control > Data List

Tester Display

Neutral SW/ Clutch SW
Body Electrical > Starting Control > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Shift Position P or N

Park/Neutral position switch status

OFF or ON

OFF: Shift lever not in P or N

ON: Shift lever in P or N

When malfunctioning, the engine will not crank.
Body Electrical > Starting Control > Data List

Tester Display

Shift Position P or N

OK:

The Techstream display changes correctly in response to the shift lever operation.

NG

GO TO STEP 25

OK

6.

CHECK FOR DTC

(a) Using the Techstream, check for certification ECU (smart key ECU assembly) DTCs.

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

Result

Proceed to

DTCs are not output

A

Smart access system with push-button start (for Start Function) DTCs are output

B
B

GO TO DIAGNOSTIC TROUBLE CODE CHART

A

7.

READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH1)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(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 if the stop light switch assembly is malfunctioning.
  • The engine cannot be started when this item is OFF.
  • If the stop light switch assembly is malfunctioning, the engine can be started by pressing and holding the engine 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 pedal operation.

NG

GO TO STEP 22

OK

8.

READ VALUE USING TECHSTREAM (STARTER REQUEST SIGNAL)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(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

Engine start request signal status

OFF or ON

OFF: The engine switch is not pressed

ON: With the shift lever in P and the brake pedal depressed, the engine switch is pressed and held
  • When the engine cannot be started due to a start request signal malfunction, OFF is displayed.
  • When the engine switch is pressed, the duration of time that ON is displayed will be extremely short. As such, the engine 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 key indicator display is displayed on the multi-information display in the combination meter assembly, and then press the engine switch.

OK:

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

NG

GO TO STEP 20

OK

9.

INSPECT ST RELAY

(a) Inspect the ST relay.

Click here

NG

REPLACE ST RELAY (STARTER RELAY ASSEMBLY)
OK

10.

INSPECT STARTER ASSEMBLY

(a) Remove the starter assembly.

Click here

(b) Inspect the starter assembly.

Click here

NG

REPLACE STARTER ASSEMBLY

OK

11.

CHECK HARNESS AND CONNECTOR (BATTERY - STARTER ASSEMBLY AND ST RELAY)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

D71-1 (B) - Body ground

Always

11 to 14 V

5 (ST relay) - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

12.

CHECK HARNESS AND CONNECTOR (ST RELAY - BODY GROUND)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

1 (ST relay) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

13.

CHECK HARNESS AND CONNECTOR (STARTER ASSEMBLY - ST RELAY)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 (ST relay) - D21-1 (ST)

Always

Below 1 Ω

3 (ST relay) or D21-1 (ST) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

14.

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A74-20 (STA) - Body ground

Engine switch pressed and held with brake pedal depressed (starter on) → Approximately 1 second after engine switch released (starter off)

6 V or higher* → 1.0 V or less

HINT:

*: While the engine is cranking, the battery voltage may drop to approximately 6 V.

*a

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))
NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

OK

15.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ST RELAY)

(a) Disconnect the A74 certification ECU (smart key ECU assembly) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A74-20 (STA) - 2 (ST relay)

Always

Below 1 Ω

A74-20 (STA) or 2 (ST relay) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

16.

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Reconnect the A74 certification ECU (smart key ECU assembly) connector.

*a

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A74-9 (STAR) - Body ground

Engine switch pressed and held with brake pedal depressed (starter on) → Approximately 1 second after engine switch released (starter off)

6 V or higher* → 1.0 V or less

HINT:

*: While the engine is cranking, the battery voltage may drop to approximately 6 V.

NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

OK

17.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - PARK/NEUTRAL POSITION SWITCH ASSEMBLY)

(a) Disconnect the A74 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the D15 park/neutral position switch assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A74-9 (STAR) - D15-4 (B)

Always

Below 1 Ω

A74-9 (STAR) or D15-4 (B) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

18.

CHECK HARNESS AND CONNECTOR (PARK/NEUTRAL POSITION SWITCH ASSEMBLY - ST RELAY (STARTER RELAY ASSEMBLY)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

D15-9 (L) - 2 (ST relay)

Always

Below 1 Ω

D15-9 (L) or 2 (ST relay) - Body ground

Always

10 kΩ or higher
OK

GO TO SFI SYSTEM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

19.

INSPECT TRANSMITTER BATTERY

(a) Inspect the transmitter battery.

Click here

NOTICE:

Do not wrap the lead wire ground 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.

OK

REPLACE ELECTRICAL KEY TRANSMITTER SUB-ASSEMBLY
NG

REPLACE TRANSMITTER BATTERY

20.

CHECK STEERING LOCK

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

OK:

The steering unlocks.

NG

GO TO STEERING LOCK SYSTEM (UNABLE TO UNLOCK STEERING)

OK

21.

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 engine 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).

OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

GO TO IMMOBILISER SYSTEM (PROBLEM SYMPTOMS TABLE)

22.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - POWER SUPPLY AND BODY GROUND)

(a) Disconnect the A55 stop light switch assembly connector.

*a

Front view of wire harness connector

(to Stop Light Switch Assembly)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A55-1 (B) - Body ground

Always

11 to 14 V

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A55-3 (GND) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

23.

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

(a) Disconnect the R1 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the A37 ECM connector.

(c) Disconnect the A41 skid control ECU (brake actuator assembly) connector.

(d) Disconnect the J22 transmission floor shift assembly connector.

(e) Disconnect the 1D semiconductor pwr integration ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

R1-25 (STP1) - A55-2 (L)

Always

Below 1 Ω

R1-25 (STP1) or A55-2 (L) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

24.

INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Inspect the stop light switch assembly.

Click here

OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

REPLACE STOP LIGHT SWITCH ASSEMBLY

25.

INSPECT PARK/NEUTRAL POSITION SWITCH ASSEMBLY

(a) Remove the park/neutral position switch assembly.

Click here

(b) Inspect the park/neutral position switch assembly.

Click here

NG

REPLACE PARK/NEUTRAL POSITION SWITCH ASSEMBLY

OK

26.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - PARK/NEUTRAL POSITION SWITCH ASSEMBLY)

(a) Disconnect the A74 certification ECU (smart key ECU assembly) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A74-9 (STAR) - D15-4 (B)

Always

Below 1 Ω

A74-9 (STAR) or D15-4 (B) - Body ground

Always

10 kΩ or higher
OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
    Lost Communication with ECM / PCM (U0100,U0140,U0142,U0155,U1117)
    DESCRIPTION These DTCs are stored when there is a CAN communication malfunction between the certification ECU (smart key ECU assembly), ECM, main body ECU (multiplex network body ECU) or combination m ...

    Power Source Mode does not Change to ON (IG and ACC)
    DESCRIPTION If any of the following operations are performed, the certification ECU (smart key ECU assembly) receives a signal, and changes the power source mode. With the electrical key transmitte ...

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    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

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