LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2021 >> NX 300h Base >> Repair and Diagnosis >> Engine Mechanical >> Starter >> Smart Access System With Push-Button Start (For Start Function) - Diagnostic Codes & Symptom Tests >> SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function) >> Power Source Mode does not Change to ON (IG) [10/2014 - ] >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Power Source Mode does not Change to ON (IG) [10/2014 - ]: Procedure

  1. CHECK FOR DTC 
    1. Using the Techstream, check for DTCs.

      Body Electrical > Power Source Control > Trouble Codes 

      Body Electrical > Smart Access > Trouble Codes 

      Result

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

    Result: 

    B 

    GO TO DIAGNOSTIC TROUBLE CODE CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2014 - 10/2019]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2019 - ] 

    Result: 

    A 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY) 
    1. Disconnect the I51 certification ECU (smart key ECU assembly) connector.
    2. Disconnect the 4C and 4D instrument panel junction block assembly connectors.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      I51-3 (IG1D) - 4C-44 Always Below 1 Ω
      4D-9 - Body ground Always Below 1 Ω
      I51-3 (IG1D) or 4C-44 - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY - IG1 RELAY) 
    1. Remove the IG1 relay.
    2. Disconnect the 4B instrument panel junction block assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      4B-46 - 1 (IG1 relay) Always Below 1 Ω
      2 (IG1 relay) - Body ground Always Below 1 Ω
      4B-46 or 1 (IG1 relay) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY - IG2-MAIN RELAY) 
    1. Disconnect the 4B instrument panel junction block assembly connector.
    2. Remove the IG2-MAIN relay.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      4B-55 - 1 (IG2-MAIN relay) Always Below 1 Ω
      2 (IG2-MAIN relay) - Body ground Always Below 1 Ω
      4B-55 or 1 (IG2-MAIN relay) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CHECK INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY (IG1 NO. 1, IG1 NO. 2, IG1 NO. 3 RELAY) 
    1. Remove the instrument panel junction block assembly.

      Refer to REMOVAL [10/2014 - 05/2019] , or refer to REMOVAL [05/2019 - ]

    2. Measure the resistance according to the value(s) in the table below.
      GTY519669Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component without harness connected
      (Instrument Panel Junction Block Assembly)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      4C-44 - 4D-9 20°C (68°F) 87.32 to 127.14 Ω
      4F-1 - 4C-25 Auxiliary battery voltage applied to terminals 4C-44 and 4D-9 Below 1 Ω
      Auxiliary battery voltage not applied to terminals 4C-44 and 4D-9 10 kΩ or higher
      4F-1 - 4C-45 Auxiliary battery voltage applied to terminals 4C-44 and 4D-9 Below 1 Ω
      Auxiliary battery voltage not applied to terminals 4C-44 and 4D-9 10 kΩ or higher
      4F-1 - 4B-50 Auxiliary battery voltage applied to terminals 4C-44 and 4D-9 Below 1 Ω
      Auxiliary battery voltage not applied to terminals 4C-44 and 4D-9 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [10/2014 - 05/2019]  , or refer to  REMOVAL [05/2019 - ] 

    Result: 

    OK 

    See step  6

  6. INSPECT IG1 RELAY 
    1. Remove the IG1 relay.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 - 5 Auxiliary battery voltage applied to terminals 1 and 2 Below 1 Ω
      Auxiliary battery voltage not applied to terminals 1 and 2 10 kΩ or higher
      GTY464377Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 IG1 Relay

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE IG1 RELAY 

    Result: 

    OK 

    See step  7

  7. INSPECT IG2-MAIN RELAY 
    1. Remove the IG2-MAIN relay.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 - 5 Auxiliary battery voltage applied to terminals 1 and 2 Below 1 Ω
      Auxiliary battery voltage not applied to terminals 1 and 2 10 kΩ or higher
      GTY464377Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 IG2-MAIN Relay

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE IG1 MAIN RELAY 

    Result: 

    OK 

    See step  8

  8. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) 
    1. Reconnect the I51 certification ECU (smart key ECU assembly) connector.
    2. Install the instrument panel junction block assembly.

      Refer to INSTALLATION [10/2014 - 05/2019] , or refer to INSTALLATION [05/2019 - ]

    3. Install the IG1 relay.
    4. Install the IG2-MAIN relay.
    5. Measure the voltage according to the value(s) in the table below.
      GTY516487Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Certification ECU (Smart Key ECU Assembly))

      Standard Voltage

      Tester Connection Condition Specified Condition
      I51-3 (IG1D) - Body ground Power switch on (ACC) → Power switch on (IG) 1 V or less → 9 V or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2014 - 09/2017]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2017 - 05/2019]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [05/2019 - 10/2019]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2019 - 07/2020]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [07/2020 - ] 

    Result: 

    NG 

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [10/2014 - ] 

scientia non olet · About LEMON Manuals