Parts for your 2017 Subaru Outback-Temperature sensors

2017 Subaru Outback temperature sensors – what they do and how to look after them

Temperature sensors are absolutely fitted to the 2017 Subaru Outback (BS series) and they’re central to how the car runs. Subaru’s Factory Service Manual for 2015–2019 Outback/Legacy outlines the Engine Coolant Temperature (ECT) sensor in the FB25 2.5i and EZ36 3.6R, the Intake Air Temperature (IAT) element within the MAF, climate-control ambient and evaporator sensors, and the CVT fluid temperature sensors in the TR580/TR690 transmissions. The Subaru Owner’s Manual also shows the outside temperature display sensor, and standard OBD‑II (SAE J1979) data includes PID 05 for coolant temperature—clear technical confirmation that temperature sensors are used throughout this model.

In day-to-day driving, these sensors let the engine computer trim fuel and ignition, manage the radiator fans, and keep the CVT and cabin climate happy. If the ECT reads too cold, the engine can run rich, chew through fuel, and feel doughy. If it reads too hot, fans may run constantly and the dash gauge can scare the daylights out of anyone under the bonnet.

They’re not “regular replacement” items, but they do benefit from smart servicing:

• During coolant changes, scan live data to confirm the ECT tracks smoothly from ambient to operating temperature (roughly mid‑80s to low‑90s °C on a gentle drive). Any wild jumps or fixed values are red flags.
• Inspect connectors for green crust, coolant wicking, or broken locks—especially around the thermostat housing area.
• If replacing the ECT, let the engine cool, relieve system pressure, use the correct Subaru coolant, fit a new sealing washer, and tighten to the Factory Service Manual spec. Bleed the system properly to avoid air pockets.
• The IAT (in the MAF) and the ambient sensor up front can be upset by dust, bugs, or minor front-end knocks. Gentle cleaning and proper clip routing go a long way.
• CVT temperature sensors are internal, they’re monitored during fluid services to ensure correct change temperatures. Replacement typically requires transmission disassembly, so it’s a diagnostic step rather than routine maintenance.

When to suspect a crook temp sensor? Look for a Check Engine Light with codes like P0115–P0119, hard cold starts, black exhaust on start-up, a lazy heater, fans running flat-out, or a temp gauge that doesn’t make sense. For most owners, a quick scan during scheduled servicing is the easiest way to catch issues early and keep the Outback running sweet across Aussie and Kiwi climates.

Where is the engine coolant temperature sensor on a 2017 Outback?

On the 2.5i FB25, the ECT sensor is threaded into the coolant passage near the thermostat housing at the front of the engine. On the 3.6R EZ36 it’s similarly positioned in a coolant crossover. Access improves with the engine cool, the intake snorkel removed, and a proper deep socket. Always refit with a new sealing washer and bleed the coolant system after work.

Does the 2017 Outback have a transmission fluid temperature sensor, and can it be replaced?

Yes. Both TR580 (2.5i) and TR690 (3.6R) CVTs monitor transmission fluid temperature. These sensors are internal to the transmission or valve body. They’re not a routine service item and aren’t typically replaced unless diagnostics point squarely at a sensor fault—most temperature-related CVT issues are fluid, cooling, or control related.

What should the ECT reading look like on a scan tool?

Cold start should be close to ambient. As the engine warms, the reading should climb steadily without sudden spikes. On a mild day after a normal drive, expect mid‑80s to low‑90s °C with the thermostat open and fans cycling as needed. Irregular jumps, a stuck reading, or overheat values with a cool radiator hint at sensor, wiring, or coolant flow faults.