Parts for your 2008 Subaru Legacy-Temperature sensors

2008 Subaru Legacy temperature sensors

Temperature sensors absolutely are fitted and relevant on the 2008 Subaru Legacy. The Subaru Factory Service Manual for the 2008 model (Engine Diagnostics and HVAC sections) details the Engine Coolant Temperature (ECT) sensor and related control logic. Subaru Technical Information System wiring diagrams show an Intake Air Temperature (IAT) sensor (often integrated with the MAF on EJ engines), an ambient air temperature sensor for the climate control/outside temp display, and an Automatic Transmission Fluid (ATF) temperature sensor on auto models. Standard OBD‑II diagnostics for this car also include temperature-sensor DTCs such as P0115–P0119 (ECT), P0110 (IAT), and P0711 (ATF temp), confirming these sensors are used across the range.

On a 2008 Legacy, temperature sensors help the engine and gearbox behave properly across Aussie and Kiwi conditions—from frosty mornings to scorching arvos. The ECT sensor tells the engine computer how hot the coolant is so it can set fuel, ignition timing, idle speed, and when to switch the radiator fans. The IAT sensor helps with fuel trim by tracking incoming air density. The ambient sensor feeds the climate control and outside temperature display. Autos rely on an ATF temp sensor so the transmission control module can protect the gearbox when fluid gets too hot.

• Engine Coolant Temperature (ECT): Fuelling, timing, idle, radiator fan control, overheat warnings.
• Intake Air Temperature (IAT): Air‑fuel calculations, cold‑start enrichment, knock avoidance.
• Ambient temperature (HVAC/cluster): Climate control performance and outside temp read‑out.
• ATF temperature (auto only): Shift strategy and thermal protection.

If a sensor goes south, drivers may see hard cold starts, high idle, rich running, the thermo fans stuck on, lazy A/C, or a Check Engine Light with codes like P0115 or P0110. Servicing is straightforward: sensors aren’t routine “consumables”, but they should be inspected whenever the cooling system, intake, or transmission is serviced. Check connectors for corrosion, brittle housings, and damaged loom sections. When replacing an ECT sensor, use a quality OEM‑spec part, fit a new sealing washer or O‑ring, avoid sealant unless the manual specifies it, torque to spec, and bleed the cooling system properly. For IAT integrated with the MAF, clean only with MAF‑safe cleaner and replace the unit if readings drift. The ATF temp sensor is typically internal, diagnosis comes first, as the repair may require pan or valve‑body access. Keeping radiator/condenser fins clean and coolant/ATF fresh helps sensors read true and keeps the Legacy happy on long Kiwi or Aussie road trips.

Popular questions about 2008 Subaru Legacy temperature sensors

Where is the engine coolant temperature sensor located?
The ECT sensor on most 2008 Legacy EJ25 engines is threaded into the coolant crossover/pipe near the thermostat housing or at the coolant outlet area on the front/top of the engine. Access is usually from above with the intake snorkel removed. Exact location can vary by engine and market, so checking the service manual or a verified diagram is best.

How do you tell a bad temperature sensor from a bad thermostat?
A stuck-closed thermostat typically causes rapid overheating and top hose staying cool until it suddenly gets very hot, while a failed ECT sensor may cause rich running, high idle, fan operation at odd times, and a Check Engine Light with P0115–P0119. Comparing live scan data (coolant temp vs actual radiator/engine warmth) helps separate sensor faults from mechanical thermostat issues.

Does the 2008 Legacy have more than one temperature sensor?
Yes. Beyond the ECT, there’s an IAT sensor (often built into the MAF), an ambient air temperature sensor for HVAC/outside temp display, and an ATF temp sensor on automatic models. Each serves a different control system, so a fault in one doesn’t necessarily affect the others.