Parts for your 2009 Toyota Aurion-Temperature sensors

2009 Toyota Aurion temperature sensors — what they do and how to look after them

Temperature sensors are absolutely fitted to the 2009 Toyota Aurion (GSV40, 2GR‑FE V6). Toyota’s factory Repair Manual and Electrical Wiring Diagram for the Aurion, along with the New Car Features (NCF) guide for the 2GR‑FE and U660E automatic, detail several temperature sensors used for engine, transmission and climate control. These include the engine coolant temperature (ECT) sensor, the intake air temperature (IAT) element within the MAF sensor, the ambient (outside) air temp sensor for the HVAC and instrument display, the evaporator thermistor, and the automatic transmission fluid (ATF) temperature sensor inside the transaxle.

On this Aurion, temperature sensors feed live data to the engine and transmission control modules so the car can start cleanly when cold, run efficiently once warm, manage cooling fans, protect the drivetrain, and keep the cabin comfy. The ECT sensor, threaded into the water outlet/thermostat housing, tells the ECU how hot the coolant is, the IAT helps trim fuel on hot or cool days, the ambient sensor up front informs the A/C and the dash, the evaporator sensor prevents the core from icing, and the ATF sensor helps the auto choose shift timing and line pressure, especially during warm‑up or towing.

• Common signs a temp sensor is crook: hard cold starts, rough idle, poor fuel economy, cooling fans stuck on, a dead temp gauge, harsh shifts, or fault codes like P0115–P0119.
• Basic maintenance: during regular servicing, check connectors for green corrosion, brittle plastic clips and rubbed wiring near the radiator support and under the airbox.

Replacement tips vary by sensor. For the ECT, let it cool fully, relieve system pressure, drain a little coolant, then swap the sensor and new sealing washer/O‑ring as specified. Refill with Toyota Super Long Life Coolant (pink) and bleed air. A scan tool helps verify the new sensor reads plausibly (cold start near ambient, then rising smoothly). The IAT on the Aurion is part of the MAF, if readings are off, try proper MAF cleaner (no touching the element) before replacement. The ambient sensor lives behind the bumper/condenser area and often breaks after minor front‑end knocks—easy fix, but make sure the mounting tab points into free airflow. The A/T fluid temperature sensor isn’t a routine service item, it’s integrated in the transmission’s internal harness/valve body, and level checks are done with the fluid at a specific temperature using a scan tool. Quality, known‑brand parts (or genuine) are the go, and always clear codes and road‑test to confirm normal fan, gauge and shift behaviour after any work.

• Where is the engine coolant temperature sensor on a 2009 Toyota Aurion?

  It’s threaded into the water outlet/thermostat housing on the 2GR‑FE, at the front of the engine under the bonnet (radiator side on this transverse V6). You’ll see a two‑pin connector and a small brass sensor body. Access is usually from above with the engine cover off.

  If unsure, follow the upper radiator hose to the housing, the ECT sits nearby. Always let it cool before unplugging.

• What symptoms point to a faulty Aurion temperature sensor?

  Cold start enrichment all wrong (hard start, high idle), fans running constantly, black smoke, lousy economy, temp gauge not moving, or the A/C cycling oddly. The ECU often stores codes like P0117 or P0118 for the ECT, and live data will show implausible values (e.g., -40°C or 130°C).

  A quick scan and wiggle‑test of the connector will usually separate a bad sensor from a wiring drama.

• Does a new temperature sensor need programming?

  No programming is required for the ECT, IAT (within the MAF), or the ambient sensor on a 2009 Aurion. Fit the new part, ensure good connections, top up coolant if applicable, then clear codes and verify live data.

  Transmission fluid temperature checks do need a scan tool to confirm the correct ATF level at the specified temperature, but that’s a service procedure rather than programming.