Parts for your 2009 Lexus Is-Temperature sensors

2009 Lexus IS Temperature Sensors

Temperature sensors are absolutely relevant and fitted to the 2009 Lexus IS. Technical documentation from Toyota/Lexus TIS (Technical Information System) for the 2009 IS 250/350 and IS F, including the Repair Manual (SFI: ECT Sensor, DTC P0115–P0119, IAT circuits P0112–P0113) and New Car Features, details multiple thermistor-based sensors used across engine, transmission, and climate control systems. The Lexus parts catalogue for these models further lists the Engine Coolant Temperature (ECT) sensor and ambient air temperature sensor, confirming their use.

• Engine Coolant Temperature (ECT) sensor – feeds the ECM for fuelling, ignition timing, fan operation, and overheat protection.
• Intake Air Temperature (IAT) sensor – typically integrated in the MAF sensor, informs air density corrections.
• Ambient Air Temperature sensor – up front near the condenser, used by A/C and the outside temp display.
• A/C evaporator temperature sensor – prevents evaporator icing and stabilises cabin comfort.
• Automatic transmission fluid temperature sensor (auto models) – manages shift strategy and protection.

On the 2009 Lexus IS, these sensors quietly keep the car running sweet as. The ECT sensor lets the engine know when it’s cold for smooth starts and when it’s hot so the fans kick in. The IAT helps fine‑tune fuelling as the weather swings from a frosty morning to a scorching arvo. HVAC sensors make sure the climate control doesn’t freeze the evaporator and that the outside temp on the cluster isn’t telling porkies.

They’re not a regular “replace by kilometres” item, they’re replaced when faulty. Typical symptoms include hard cold starts, poor fuel economy, lazy or constantly running radiator fans, odd gauge readings, A/C misbehaviour, or a check engine light with codes like P0115–P0119 (ECT), P0112–P0113 (IAT), or HVAC codes for ambient/evaporator sensors.

ECT sensor replacement basics: work on a stone‑cold engine, depressurise the cooling system, and catch coolant properly. The ECT usually threads into the water outlet/thermostat housing. Swap the sensor and seal, reconnect the plug, then refill with Toyota Super Long Life Coolant (pink) and bleed the system with the heater on HOT. Check for leaks and verify the fans cycle normally.

For the IAT (integrated with the MAF), don’t touch the sensing element. If it’s contaminated, use proper MAF cleaner only—no compressed air blasts. Ambient sensors live in the front bumper and can get knocked in minor nudges, replacement is simple and restores accurate outside temp and A/C performance.

1. Scan first—diagnostics save guesswork.
2. Use OEM‑quality sensors, cheapies can read off and cause dramas.
3. After any cooling system work, bleed thoroughly to avoid hot spots and false ECT readings.

FAQs

Where is the coolant temperature sensor on a 2009 Lexus IS?
The ECT sensor is typically threaded into the water outlet/thermostat housing on the engine. On IS 250/350 it’s near the upper radiator hose area. Access is straightforward with basic tools, but let the engine cool fully and be ready to top up and bleed coolant after replacement.

Can a temperature sensor be cleaned, or does it need replacing?
ECT and ambient sensors are sealed thermistors—if they read incorrectly, replacement is the go. The IAT, often inside the MAF, can be carefully cleaned with MAF cleaner if it’s just dirty. If cleaning doesn’t restore proper readings, replace the relevant sensor or the MAF assembly.

What coolant should be used after ECT sensor replacement, and how is bleeding done?
Use Toyota Super Long Life Coolant (pink), premixed or a 50/50 demineralised water blend if concentrate. Fill slowly, set the heater to HOT, run the engine, and squeeze the upper hose to burp air. Top up the radiator and overflow bottle as bubbles clear, then recheck levels after a short drive.