Parts for your 2016 Subaru Legacy-Temperature sensors

2016 Subaru Legacy temperature-sensors: what they do and how to look after them

Temperature-sensors absolutely are used on the 2016 Subaru Legacy. Factory documentation such as the Subaru Legacy/Outback 2015–2019 Service Manual (Engine Diagnostics for FB25 and EZ36), the New Car Features guide, and the OEM wiring diagrams all show multiple temperature inputs: the engine coolant temperature (ECT) sensor, intake air temperature (IAT) sensor, ambient air temperature sensor, transmission fluid temperature sensor in the CVT/5EAT, and A/C thermistors. These are critical for engine management, emissions, transmission control and HVAC operation.

On this model, temperature-sensors tell the engine computer how warm the coolant and intake air are, so it can sort out cold starts, fuelling, ignition timing and idle speed. They also let the CVT manage line pressure and shift strategy based on fluid temp, and help the climate control aim for the set cabin temperature without fogging the windscreen. The dash gauge and radiator fans rely on the same data. Without good sensor readings, the Legacy can run rich, feel doughy, kick the fans on early, or throw fault codes like P0115–P0119 for the ECT circuit, as listed in the Subaru service manual.

These sensors aren’t typical “replace every X kilometres” items. They’re replaced when faulty, contaminated, physically damaged, or if wiring/connectors deteriorate. During regular servicing, a tech will usually:

• Scan live data cold and hot to confirm realistic readings (cold ECT/IAT near ambient, smooth warm-up curve).
• Inspect connectors and looms for corrosion, oil wicking or rub-through.
• Keep the cooling system healthy with the correct Subaru long-life coolant and proper bleed procedures, as poor coolant condition can shorten ECT sensor life.

If an ECT sensor needs swapping, it’s a straightforward job for a workshop: let the engine cool, relieve pressure, drain a little coolant, unplug, remove the sensor, then install the new OEM-spec unit with a fresh seal and torque it to spec from the Subaru manual. After refilling and bleeding the cooling system, they’ll verify temperature readings and radiator fan operation. Using the genuine part number that matches the VIN helps avoid calibration mismatches. The same logic applies to IAT and ambient sensors—fix the cause (e.g., broken clip, impact damage) and refit correctly so the sensor “sees” true airflow or ambient conditions.

For owners, the best maintenance is preventative: stick to the service schedule, fix any coolant leaks early, and don’t ignore a check engine light or a temp gauge that behaves oddly. A quick scan and a look at the data usually confirm whether a temperature-sensor is the culprit or if something upstream—like low coolant or a stuck thermostat—is to blame.

Popular questions about 2016 Subaru Legacy temperature-sensors

Do temperature-sensors cause hard starting or rough running when cold?

They can. If the ECT sensor reports the engine as warmer or colder than it really is, fuelling and idle strategy go out of whack. Typical signs include rich smell, high idle, poor economy and a check engine light. A scan of live data from cold start is the quick way to confirm.

Should temperature-sensors be replaced as routine maintenance?

No. On this model they’re condition-based items. Replace them only if faulty, contaminated, physically damaged, or when diagnostics point to a sensor or connector issue. Keeping the correct coolant in good nick and wiring intact goes a long way.

What’s the best way to diagnose a dodgy temperature-sensor on a Legacy?

Use a scan tool to compare ECT and IAT to actual ambient temperature when cold, then watch the warm-up curve. Check for related DTCs (like P0115–P0119), inspect the plug and wiring, and make sure the cooling system is full and bled. Repairs without scanning often miss the real cause.