Parts for your 2010 Subaru Forester-Temperature sensors

2010 Subaru Forester temperature sensors — what they do and when to service them

Temperature sensors are absolutely used on the 2010 Subaru Forester. The Subaru Factory Service Manual (FSM) for the SH series (2009–2013), as accessed via Subaru’s Technical Information System, lists multiple temperature inputs: the engine coolant temperature (ECT) sensor, an intake air temperature (IAT) sensor integrated with the MAF, an automatic transmission fluid (ATF) temperature sensor, plus ambient and A/C-related sensors for climate control. These are also reflected in standard OBD‑II diagnostics (SAE J1979) with codes such as P0115–P0119 (ECT), P0128 (coolant thermostat/temperature), and P0113 (IAT). Workshop references such as the Haynes manual for 2009–2014 Forester cover the same components and test procedures.

This Forester relies on a handful of temperature sensors to run sweet as. The ECT sensor is the big one for the engine computer. It helps manage cold starts, fuel delivery, ignition timing, radiator fan operation, and the dash gauge. The IAT sensor tells the ECU how dense the air is, so it can trim fuelling. If it’s an auto, the ATF temperature sensor informs shift timing and line pressure. Ambient and evaporator sensors keep the air‑con behaving, while turbo XT models may also monitor exhaust temps for protection.

When these sensors drift or fail, the car can be a bit of a diva: hard cold starts, rich running, high idle, dodgy economy, radiator fans stuck on, erratic temp gauge, harsh shifts, or air‑con that can’t make up its mind. If the check engine light pops with P0115–P0119, P0128 or P0113, it’s time to check live data.

At service time, a quick health check pays off:

• Scan live data from cold, ECT and IAT should be close to ambient, then rise naturally.
• Inspect plugs and looms for corrosion or coolant staining around the ECT.
• Keep coolant fresh to Subaru spec and bleed air properly — sensors hate steam pockets.
• MAF/IAT can be cleaned with MAF-safe cleaner only, don’t touch the element.

Replacing the ECT on the EJ25 is straightforward for a competent tech: cool engine, relieve pressure, unplug, swap the sensor, and top up/bleed coolant. Use an OE-quality sensor and tighten to the FSM torque (around 18 N·m, confirm for your engine code). ATF temperature sensors are internal to the transmission, focus on correct fluid and cooling system service rather than proactive replacement. Ambient/A/C sensors are up front near the grille or within the HVAC box, if the dash temp reads wildly off, inspect for damage or open circuits.

There’s no fixed kilometre interval for swapping temperature sensors, but checking them every major service and any time related fault codes appear will keep the Forester running reliably across Aussie and Kiwi conditions.

FAQs

Where is the engine coolant temperature sensor on a 2010 Forester?
On EJ25 engines it’s mounted on the coolant crossover/pipe near the thermostat housing under the intake area. Access varies with intake ducting, a deep socket helps. Turbo XT layouts may look a bit different but location remains on the coolant passage near the top of the engine.

What symptoms point to a bad temperature sensor?
Think hard cold starts, rough idle, poor fuel economy, radiator fans running constantly, inaccurate temp gauge, harsh auto shifts, and fault codes like P0115–P0119 or P0128. Live data that doesn’t match ambient when the engine’s stone cold is a giveaway.

Can temperature sensors be cleaned or should they be replaced?
The ECT and most HVAC sensors are sealed thermistors — replace if faulty. The IAT (inside the MAF) can be gently cleaned with MAF-safe cleaner. If contamination returns, check for crankcase ventilation or air filter issues causing deposits.