LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2007 >> Avalon XLS >> Repair and Diagnosis >> Electrical >> Starter >> Starting System >> Smart Key System >> DTC B2278 Engine Switch Circuit Malfunction >> Inspection Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Inspection Procedure

  1. READ VALUE OF INTELLIGENT TESTER 
    1. Connect the intelligent tester to the DLC3.
    2. Turn the engine switch on (IG) and press the intelligent tester main switch on.
    3. Read the Data List according to the displays on the tester.

    PWR SOURCE CTRL (Power source control ECU): 

    DATA LIST

    Item Measurement Item / Display (Range) Normal Condition Diagnostic Note
    START SW1 Status of start switch 1 / ON or OFF ON: Engine switch ON (IG) OFF: Engine switch OFF (IG) -
    START SW2 Status of start switch 2/ ON or OFF ON: Engine switch ON (IG) OFF: Engine switch OFF (IG) -

    OK: 

    "ON" (engine switch on (IG)) appears on the screen 

    Result 

    RESULT

    Condition Proceed to
    NG C
    OK (When troubleshooting according to the PROBLEM SYMPTOM TABLE) B
    OK (When troubleshooting according to the DTC chart) A

    B: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN  PROBLEM SYMPTOMS TABLE  

    C:  Go to step 2 below.

    A: REPLACE POWER SOURCE CONTROL ECU 

  2. INSPECT ENGINE SWITCH 
    1. Disconnect the D21 switch connector.
    2. Measure the resistance according to the value(s) in the table below.
      Fig 1: Identifying D21 Connector Terminals
      G05000356Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Resistance

      RESISTANCE SPECIFICATION

      Terminal No. (Symbol) Switch Condition Specified value
      D21-2(SS2)-D21-5 (GND) Free 10 kΩ or higher
      Pushed (Hold) Below 1 Ω
      D21-7(SS1)-D21-5 (GND) Free 10 kΩ or higher
      Pushed (Hold) Below 1 Ω

    NG: REPLACE ENGINE SWITCH 

    OK: Go to Next Step 

  3. CHECK WIRE HARNESS (ENGINE SWITCH - POWER SOURCE CONTROL ECU AND BODY GROUND) 
    1. Disconnect the D21 switch connector.
    2. Disconnect the D44 ECU connector.
    3. Measure the resistance of the wire harness side connectors.
      Fig 2: Disconnecting D44 ECU Connector Terminals SSW1 And SSW
      G05000357Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      Fig 3: Identifying D21 Connector Terminals
      G05000358Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Resistance 

      RESISTANCE SPECIFICATION

      Terminal No. (Symbol) Specified Condition
      D21-7 (SS1) - D44-14 (SSW1) Below 1 Ω
      D21-2 (SS2) - D44-37 (SSW2) Below 1 Ω
      D21-5 (GND) - Body ground Below 1 Ω
      D21-7 (SS1) or D44-14 (SSW1) - Body ground 10 kΩ or higher
      D21-2 (SS2) or D44-37 (SSW2) - Body ground 10 kΩ or higher

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: REPLACE ENGINE SWITCH 

scientia non olet · About LEMON Manuals