Where is the coolant temperature sensor on a Lexus ES330?
The coolant temperature sensor (CTS) in the Lexus ES330 is mounted in the thermostat housing at the front of the engine, on the passenger side, where the upper radiator hose attaches. This small sensor tells the engine computer and the gauge how hot the engine is running. Knowing its exact position helps with diagnostics, maintenance, and replacement.
Locating the sensor on the 1MZ-FE engine
In the ES330, which uses the 3.3L 1MZ-FE V6, the CTS is threaded into the thermostat housing at the front of the engine. Access is easiest from above, and you may need to remove the air intake ducting or engine covers to see the housing clearly.
To help you locate it, follow these steps:
- Open the hood and clear any obstructions around the front of the engine to view the area where the upper radiator hose connects to the engine.
- Trace the upper radiator hose to the thermostat housing; the CTS will be screwed into the housing at or near this junction.
- Look for a small metal or plastic sensor with an electrical connector plugged into the side or top of the housing.
- Disconnect the electrical connector, then use a suitable wrench or socket to carefully unscrew the sensor from the housing.
Locating the CTS in this spot is consistent across most ES330 models within the late 2000s, but always consult your specific owner's manual or a service manual if you encounter a different engine bay layout.
Testing or replacing the CTS
Before you test or replace the sensor, prepare the vehicle and gather the right tools. You’ll want to avoid hot coolant spills and protect against electrical shorts.
- Disconnect the battery and allow the engine to cool before touching cooling system components.
- Unplug the CTS harness and inspect the electrical connector for corrosion or bent pins; clean or replace as needed.
- If testing, use a multimeter to check resistance (or consult a service manual for the correct values at known temperatures) or scan the ECU for related coolant temperature codes (such as those indicating sensor, wiring, or circuit faults).
- If the sensor shows signs of failure (erratic gauge readings, poor starting, or engine running abnormally in cold/hot conditions), replace the CTS with an OEM or equivalent unit and re-seat the connector firmly.
After replacing or testing, reconnect the harness, fill or top off coolant if needed, and perform a short engine run to verify normal gauge operation and that there are no leaks around the thermostat housing.
Additional notes and tips
If you have trouble locating the CTS or your engine bay layout differs slightly, check the service manual for your exact ES330 year and engine variant. Some models may have minor variations in sensor positioning or harness routing.
Summary
The coolant temperature sensor on a Lexus ES330 is located in the thermostat housing at the front of the 3.3L V6 engine, on the passenger side near the upper radiator hose. Access typically requires removing some intake components for visibility. When servicing, always work on a cool engine, disconnect the battery, inspect connectors, and replace the sensor with proper torque and sealing to ensure reliable temperature readings and engine performance.
