LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2021 >> RX 450h Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (Diagnostic Codes) (8 Of 8) & Circuit Tests) >> SFI System >> Circuit Tests >> Fuel Pump Control Circuit [10/2015 - 03/2018] >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Fuel Pump Control Circuit [10/2015 - 03/2018]: Procedure

  1. INSPECT FUEL PUMP CONTROL ECU ASSEMBLY 
    1. Remove the fuel pump control ECU assembly.

      Refer to REMOVAL [10/2015 - ]

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      S49-1 (+B) - S49-3 (GND) Always 200 Ω or higher
      S49-1 (+B) - S49-2 (FPC) Always 2 kΩ or higher
      S49-2 (FPC) - S49-3 (GND) Always 10 kΩ or higher
      S48-1 (FPG) - S49-3 (GND) Always 1 kΩ or higher
      S48-2 (FPU) - S49-3 (GND) Always 2 kΩ or higher
      S48-3 (FPV) - S49-3 (GND) Always 2 kΩ or higher
      S48-4 (FPW) - S49-3 (GND) Always 2 kΩ or higher

      HINT: 

      This procedure checks for an internal short of the fuel pump control ECU assembly when its transistor is stuck on.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE FUEL PUMP CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2015 - ] 

    Result: 

    OK 

    See step  2

  2. CHECK TERMINAL VOLTAGE (POWER SOURCE OF FUEL PUMP CONTROL ECU ASSEMBLY) 
    GTY652483Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Front view of wire harness connector
    (to Fuel Pump Control ECU Assembly)
    1. Disconnect the fuel pump control ECU assembly connector.
    2. Turn the power switch on (IG).
    3. Measure the voltage according to the value (s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      S49-1 (+B) - S49-3 (GND) Power switch on (IG) 11 to 14 V

      HINT: 

      Make a note of the measured voltage as it may be used in a following Active Test.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  7

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (FUEL PUMP CONTROL ECU ASSEMBLY - ECM ASSEMBLY) 
    1. Disconnect the fuel pump control ECU assembly connector.
    2. Disconnect the ECM assembly connector.
    3. Measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      S49-2 (FPC) - A37-41 (FPC) Always Below 1 Ω
      S49-2 (FPC) or A37-41 (FPC) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. PERFORM ACTIVE TEST USING TECHSTREAM (FUEL PUMP SINGLE PHASE ENERGIZATION) 
    GTY947351Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Component without harness connected
    (Fuel Pump Control ECU Assembly)
    1. Disconnect the S48 fuel pump control ECU assembly connector.
    2. Connect the Techstream to the DLC3.
    3. Turn the power switch on (IG).
    4. Turn the Techstream on.
    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Fuel Pump Single Phase Energization.

      Powertrain > Engine and ECT > Active Test 

      Tester Display
      Fuel Pump Single Phase Energization
    6. Operate the fuel pump control ECU assembly using the Active Test function and measure the voltage according to the value (s) in the table below.

      Standard Voltage

      Tester Connection Techstream Operation Specified Condition
      S48-2 (FPU) - Body ground U Phase 4.4 to 8.4 V*
      S48-3 (FPV) - Body ground V Phase 4.4 to 8.4 V*
      S48-4 (FPW) - Body ground W Phase 4.4 to 8.4 V*

      HINT: 

      • *: This Active Test restricts the fuel pump control ECU assembly output duty cycle to 50%. Therefore, the output voltage of the fuel pump control ECU assembly will be approximately 50% of the power source voltage measured in a previous step.
      • Before performing this inspection, check that the battery voltage is between 11 and 14 V (not depleted).

      Result

      Result Proceed to
      The U phase, V phase and W phase are all normal A
      The U phase, V phase or W phase is abnormal B
      The U phase, V phase and W phase are all abnormal C

    Result: 

    B 

    REPLACE FUEL PUMP CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2015 - ] 

    Result: 

    C 

    See step  6

    Result: 

    A 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (FUEL PUMP CONTROL ECU ASSEMBLY - FUEL PUMP (FOR LOW PRESSURE SIDE)) 
    1. Disconnect the fuel pump control ECU assembly connector.
    2. Disconnect the fuel pump (for low pressure side) connector.
    3. Measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      S48-2 (FPU) - E2-3 (BLPU) Always Below 1 Ω
      S48-3 (FPV) - E2-4 (BLPV) Always Below 1 Ω
      S48-4 (FPW) - E2-2 (BLPW) Always Below 1 Ω
      S48-2 (FPU) or E2-3 (BLPU) - Body ground and other terminals Always 10 kΩ or higher
      S48-3 (FPV) or E2-4 (BLPV) - Body ground and other terminals Always 10 kΩ or higher
      S48-4 (FPW) or E2-2 (BLPW) - Body ground and other terminals Always 10 kΩ or higher

      HINT: 

      Perform "Inspection After Repair" after replacing the fuel pump (for low pressure side).

      Refer to INITIALIZATION [10/2015 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FUEL PUMP (FOR LOW PRESSURE SIDE). Refer to  REMOVAL [10/2015 - 08/2016]  , or refer to  REMOVAL [08/2016 - 08/2019] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  6. INSPECT ECM ASSEMBLY (FPC TERMINAL) 
    GTY652480Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Front view of wire harness connector
    (to Fuel Pump Control ECU Assembly)
    1. Disconnect the fuel pump control ECU assembly connector.
    2. Connect the Techstream to the DLC3.
    3. Turn the power switch on (IG).
    4. Turn the Techstream on.
    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Fuel Pump Single Phase Energization.

      Powertrain > Engine and ECT > Active Test 

      Tester Display
      Fuel Pump Single Phase Energization
    6. Operate the fuel pump control ECU assembly using the Active Test function and measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Techstream Operation Specified Condition
      S49-2 (FPC)- Body ground Before Active Test → During Active Test Before Active Test: Resistance is stable → During Active Test: Resistance fluctuates*

      HINT: 

      *: Using the Active Test, duty control of the transistors in the ECM assembly will be performed. Due to the duty control, resistance of the FPC terminal will be unstable during the Active Test. If the resistance is stable before the Active Test and fluctuates while performing the Active Test, it can be determined that the transistor is operating. If the transistor does not operate during the Active Test, the ECM assembly may be malfunctioning.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FUEL PUMP CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2015 - ] 

    Result: 

    NG 

    REPLACE ECM ASSEMBLY. Refer to  REMOVAL [10/2015 - 08/2016]  , or refer to  REMOVAL [08/2016 - 03/2018] 

  7. CHECK HARNESS AND CONNECTOR (POWER SOURCE VOLTAGE OF FUEL PMP RELAY) 
    1. Remove the FUEL PMP relay from the engine room relay block and junction block assembly.
    2. Measure the voltage according to the value (s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      5 (FUEL PMP relay) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - FUEL PMP RELAY) 

    Result: 

    OK 

    See step  8

  8. INSPECT FUEL PMP RELAY 
    1. Inspect the FUEL PMP relay.

      Refer to PROCEDURE - Step 2

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE FUEL PMP RELAY 

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (SEMICONDUCTOR PWR INTEGRATION ECU - ECM ASSEMBLY) 
    1. Disconnect the semiconductor pwr integration ECU connector.
    2. Disconnect the ECM assembly connector.
    3. Measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      1G-6 - A37-46 (MREL) Always Below 1 Ω
      1G-6 or A37-46 (MREL) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  10

  10. CHECK HARNESS AND CONNECTOR (SEMICONDUCTOR PWR INTEGRATION ECU - FUEL PMP RELAY) 
    1. Disconnect the semiconductor pwr integration ECU connector.
    2. Remove the FUEL PMP relay from the engine room relay block and junction block assembly.
    3. Measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      1G-8 - 1 (FUEL PMP relay) Always Below 1 Ω
      1G-8 or 1 (FUEL PMP relay) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  11

  11. CHECK HARNESS AND CONNECTOR (FUEL PMP RELAY - BODY GROUND) 
    1. Remove the FUEL PMP relay from the engine room relay block and junction block assembly.
    2. Measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2 (FUEL PMP relay) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  12

  12. CHECK HARNESS AND CONNECTOR (FUEL PMP RELAY - FUEL PUMP CONTROL ECU ASSEMBLY) 
    1. Remove the FUEL PMP relay from the engine room relay block and junction block assembly.
    2. Disconnect the fuel pump control ECU assembly connector.
    3. Measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 (FUEL PMP relay) - S49-1 (+B) Always Below 1 Ω
      3 (FUEL PMP relay) or S49-1 (+B) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  13

  13. CHECK HARNESS AND CONNECTOR (FUEL PUMP CONTROL ECU ASSEMBLY - BODY GROUND) 
    1. Disconnect the fuel pump control ECU assembly connector.
    2. Measure the resistance according to the value (s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      S49-3 (GND) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO ECM POWER SOURCE CIRCUIT. Refer to  ECM Power Source Circuit [10/2015 - ]  

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

scientia non olet · About LEMON Manuals