Toyota Yaris: Smart Key System (for Start Function) / Engine does not Start

Toyota Yaris XP210 (2020-2025) Reapir and Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Key System (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 clutch pedal is depressed, the engine can be started by pressing the engine switch.

Related Data List and Active Test Items

Problem Symptom

Data List and Active Test

Engine does not start
Power Source Control
  • Neutral SW/ Clutch SW
  • Starter Relay Driving Request (Starting Control)
Smart Key
  • Immobiliser
  • Start Request
  • L Code Check
  • S Code Check

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When using the GTS with the ignition switch off, connect the GTS to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the GTS and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Key. While using the GTS, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the GTS and the vehicle.
  • If the smart key system (for Start Function) has been disabled, enable the system before performing troubleshooting.

    Click here

  • Inspect the fuses for 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 Registration.

    Click here

  • After completing repairs, confirm that the problem does not recur.
  • After performing repairs, confirm that no DTCs are output by performing "DTC Output Confirmation Operation."

PROCEDURE

1.

CHECK ENGINE SWITCH CONDITION

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

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

Result

Proceed to

Power source mode changes : Off → ACC → ON → off

A

Power source mode does not change to ACC or ON

B

Power source mode changes to ON but not to ACC

C

Power source mode changes to ACC but not to ON

D
B

GO TO OTHER PROBLEM (Power Source Mode does not Change to ON (IG and ACC))

C

GO TO OTHER PROBLEM (Power Source Mode does not Change to ON (ACC))

D

GO TO OTHER PROBLEM (Power Source Mode does not Change to ON (IG))

A

2.

READ VALUE USING GTS (NEUTRAL SW/ CLUTCH SW)

(a) Read the Data List according to the display on the GTS.

Body Electrical > Power Source Control > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Neutral Switch / Clutch Switch

State of clutch pedal

OFF or ON

OFF: Clutch pedal released

ON: Clutch pedal depressed
  • Use this item to help determine if the clutch position switch is malfunctioning.
  • The engine cannot be started when this item is "OFF".
Body Electrical > Power Source Control > Data List

Tester Display

Neutral Switch / Clutch Switch

OK:

The GTS display changes correctly in response to the clutch pedal operation.

NG

GO TO STEP 12

OK

3.

READ VALUE USING GTS (POWER SUPPLY CONDITION)

(a) Read the Data List according to the display on the GTS.

Body Electrical > Power Source Control > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Power Supply Condition

Power supply state

OFF, ACC ON, IGR ON, IGP ON or Starter ON

OFF: Ignition switch off

ACC ON: Ignition switch ACC

IGR ON: Ignition switch ON

IGP ON: Ignition switch ON

Starter ON: Sending engine start request signal

-
Body Electrical > Power Source Control > Data List

Tester Display

Power Supply Condition

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 GTS display changes correctly in response to the engine switch operation.

NG

GO TO STEP 10

OK

4.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ST NO. 1 RELAY)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

No. 1 engine room relay block assembly ST NO. 1 relay terminal 2 - Body ground

Engine switch pressed and held with clutch 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 auxiliary battery voltage may drop to approximately 6 V.

*1

No. 1 Engine Room Relay Block Assembly

(ST NO. 1 Relay Holder)
NG

GO TO STEP 9

OK

5.

CHECK HARNESS AND CONNECTOR (ST NO. 1 RELAY - AUXILIARY BATTERY AND GROUND)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

No. 1 engine room relay block assembly ST NO. 1 relay terminal 1 - Body ground

Always

Below 1 Ω

*1

No. 1 Engine Room Relay Block Assembly

(ST NO. 1 Relay Holder)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

No. 1 engine room relay block assembly ST NO. 1 relay terminal 5 - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

6.

INSPECT ST NO. 1 RELAY

Click here

NG

REPLACE ST NO. 1 RELAY
OK

7.

CHECK HARNESS AND CONNECTOR (STARTER ASSEMBLY - ST NO. 1 RELAY)

(a) Disconnect the D54 and D55 starter assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

No. 1 engine room relay block assembly ST NO. 1 relay terminal 3 - D54-1

Always

Below 1 Ω

No. 1 engine room relay block assembly ST NO. 1 relay terminal 3 - D55-1

Always

Below 1 Ω

No. 1 engine room relay block assembly ST NO. 1 relay terminal 3 or D54-1 - Other terminals and body ground

Always

10 kΩ or higher

No. 1 engine room relay block assembly ST NO. 1 relay terminal 3 or D55-1 - Other terminals and body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

8.

CHECK HARNESS AND CONNECTOR (STARTER ASSEMBLY - AUXILIARY BATTERY)

(a) Disconnect the D108 starter assembly connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

D108-1 (B) - Body ground

Always

11 to 14 V
OK

REPLACE STARTER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

9.

CHECK HARNESS AND CONNECTOR (CLUTCH START SWITCH ASSEMBLY - ST NO. 1 RELAY)

(a) Disconnect the A64 clutch start switch assembly connector.

(b) Disconnect the A67 engine stop and start ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A64-1 (L) - 2 (ST NO. 1 relay)

Always

Below 1 Ω

A64-1 (L) or 2 (ST NO. 1 relay) - Other terminals and body ground

Always

10 kΩ or higher
OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

10.

CHECK STEERING LOCK FUNCTION

(a) Check that the steering unlocks when the ignition switch is turned to ACC.

OK:

The steering unlocks.

NG

GO TO OTHER PROBLEM (Unable to Unlock Steering Wheel (Engine cannot Start))

OK

11.

CHECK SECURITY INDICATOR LIGHT (IMMOBILISER FUNCTION UNSET)

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

(b) Press the engine switch with the clutch 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 ACC.

OK:

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

OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

GO TO OTHER PROBLEM (Immobiliser System does not Operate Properly)

12.

READ VALUE USING GTS (NEUTRAL SW/ CLUTCH SW)

(a) Disconnect the A106 ECM connector.

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

Body Electrical > Power Source Control > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Neutral Switch / Clutch Switch

State of clutch pedal

OFF or ON

OFF: Clutch pedal released

ON: Clutch pedal depressed
  • Use this item to help determine if the clutch position switch is malfunctioning.
  • The engine cannot be started when this item is "OFF".
Body Electrical > Power Source Control > Data List

Tester Display

Neutral Switch / Clutch Switch

OK:

The GTS display changes correctly in response to the clutch pedal operation.

OK

REPLACE ECM

NG

13.

READ VALUE USING GTS (NEUTRAL SW/ CLUTCH SW)

(a) Disconnect the A67 engine stop and start ECU connector.

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

Body Electrical > Power Source Control > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Neutral Switch / Clutch Switch

State of clutch pedal

OFF or ON

OFF: Clutch pedal released

ON: Clutch pedal depressed
  • Use this item to help determine if the clutch position switch is malfunctioning.
  • The engine cannot be started when this item is "OFF".
Body Electrical > Power Source Control > Data List

Tester Display

Neutral Switch / Clutch Switch

OK:

The GTS display changes correctly in response to the clutch pedal operation.

OK

REPLACE ENGINE STOP AND START ECU

NG

14.

INSPECT CLUTCH START SWITCH ASSEMBLY

Click here

NG

REPLACE CLUTCH START SWITCH ASSEMBLY

OK

15.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - CLUTCH START SWITCH ASSEMBLY)

(a) Disconnect the H45 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the A64 clutch start switch assembly connector.

(c) Remove the ST NO. 1 relay.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

H45-3 (STA) - A64-1 (L)

Always

Below 1 Ω

H45-3 (STA) - A67-21 (STA)

Always

Below 1 Ω

H45-10 (STAR) - A106-23 (NSW)

Always

Below 1 Ω

H45-10 (STAR) - A64-2 (B)

Always

Below 1 Ω

H45-10 (STAR) - A67-17 (CLL)

Always

Below 1 Ω

H45-3 (STA) or A64-1 (L) - Other terminals and body ground

Always

10 kΩ or higher

H45-10 (STAR) or A106-23 (NSW) - Other terminals and body ground

Always

10 kΩ or higher

H45-10 (STAR) or A64-2 (B) - Other terminals and body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

16.

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Connect the H45 certification ECU (smart key ECU assembly) connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

H45-10 (STAR) - Body ground

Engine switch pressed and held with clutch 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 auxiliary battery voltage may drop to approximately 6 V.

NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

OK

17.

INSPECT ST NO. 1 RELAY

Click here

OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

REPLACE ST NO. 1 RELAY

    Lost Communication with ECM/PCM "A" Missing Message (U010087,U012987,U014087,U015587,U110387,U111787)

    DESCRIPTION These DTCs are stored when there is a CAN communication malfunction between the certification ECU (smart key ECU assembly) and ECM, main body ECU (multiplex network body ECU) or combination meter assembly...

    Power Source Mode does not Change to ON (IG and ACC)

    DESCRIPTION When the ignition switch cannot be turned to ACC or ON, interior verification may be abnormal or there may be a malfunction in the ACC relay or IG relay circuit...

    Other information:

    Toyota Yaris XP210 (2020-2025) Reapir and Service Manual: Parts Location


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    Toyota Yaris XP210 (2020-2025) Reapir and Service Manual: Abbreviations Used In Manual


    ABBREVIATIONS USED IN MANUAL Abbreviation Meaning ABS Anti-Lock Brake System A/C Air Conditioner AC Alternating Current ACC Accessory ACIS Acoustic Control Induction System ACM Active Control Engine Mount ACSD Automatic Cold Start Device ACT Actuator A...

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