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Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 91 (Engine Control System - Diagnostic Codes (02 Of 10)) >> SFI SYSTEM (for Gasoline Model) >> DTC P0128-00: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature); DTC P0128-07: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) Mechanical Failure [08/2023 - ] >> Caution / Notice / Hint

Caution / Notice / Hint

WARNING: This page is about a different car, the 2025 Lexus RX 350, 2024 Lexus RX 350, and 2023 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.

HINT: 

When the DTC is output, check the engine coolant temperature using the GTS. Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature. If the Coolant Temperature value is lower than the actual engine coolant temperature, the engine coolant temperature sensor circuit may be malfunctioning. In this case, check the wire harnesses and connectors (and those connections) between the ECM and the engine coolant temperature sensor first.