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Home >> Lexus >> 2025 >> NX 250 FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 109 (Engine Control System - Diagnostic Codes (P26CA-U1150)) >> SFI System >> DTC P26CA-31: Engine Coolant Pump No Signal [03/2022 - 03/2023] >> Procedure

DTC P26CA-31: Engine Coolant Pump No Signal [03/2022 - 03/2023]: Procedure

WARNING: This page is about a different car, the 2025 Lexus NX 350h, 2024 Lexus NX 350h, 2023 Lexus NX 350h, and 2022 Lexus NX 350h. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK TERMINAL VOLTAGE (POWER SOURCE OF ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING)) 
    1. Disconnect the engine water pump assembly (water inlet housing) connector.
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      B31-5 (NWP) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  8

    Result: 

    OK 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING) - BODY GROUND) 
    1. Disconnect the engine water pump assembly (water inlet housing) connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B31-3 (PGN2) - Body ground Always Below 1 Ω
      B31-6 (PGND) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK TERMINAL VOLTAGE (POWER SOURCE OF ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING)) 
    1. Disconnect the engine water pump assembly (water inlet housing) connector.
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      B31-1 (+B2) - Body ground Ignition switch ON 11 to 14 V
      B31-4 (+B) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING). Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    See step  4

  4. INSPECT EFI-MAIN NO. 3 RELAY 

    Refer to PROCEDURE - Step 4

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    REPLACE EFI-MAIN NO. 3 RELAY 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (POWER SOURCE OF EFI-MAIN NO. 3 RELAY) 
    1. Remove the EFI-MAIN NO. 3 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
      GTY1254279Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 EFI-MAIN NO. 3
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      3 (EFI-MAIN NO. 3 relay) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - EFI-MAIN NO. 3 RELAY) 

    Result: 

    OK 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 3 RELAY - BODY GROUND) 
    1. Remove the EFI-MAIN NO. 3 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      1 (EFI-MAIN NO. 3 relay) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 3 RELAY - ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING)) 
    1. Remove the EFI-MAIN NO. 3 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
    2. Disconnect the engine water pump assembly (water inlet housing) connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      5 (EFI-MAIN NO. 3 relay) - B31-1 (+B2) Always Below 1 Ω
      5 (EFI-MAIN NO. 3 relay) - B31-4 (+B) Always Below 1 Ω
      5 (EFI-MAIN NO. 3 relay), B31-1 (+B2) or B31-4 (+B) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI-MAIN NO. 1 RELAY - EFI-MAIN NO. 3 RELAY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  8. CHECK HARNESS AND CONNECTOR (ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING) - ECM) 
    1. Disconnect the engine water pump assembly (water inlet housing) connector.
    2. Disconnect the ECM connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B31-5 (NWP) - B48-51 (WPI) Always Below 1 Ω
      B31-5 (NWP) or B48-51 (WPI) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE ECM. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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