Parts for your 2020 Subaru Impreza-Temperature sensors

2020 Subaru Impreza temperature sensors — what they do and how to look after them

Temperature sensors are absolutely used on the 2020 Subaru Impreza and they’re critical to how the car runs. Technical sources including the Subaru Factory Service Manual via the Subaru Technical Information System (STIS) confirm the car is fitted with multiple temperature sensors: an Engine Coolant Temperature (ECT) sensor in the engine management system, an Intake Air Temperature (IAT) sensor (integrated with the MAF on this model), an Ambient Air Temperature sensor for the auto A/C, and an ATF temperature sensor within the Lineartronic CVT (TR580) control system. See: FSM Engine/Engine Control/Diagnostics (ECT & IAT), HVAC Auto A/C (Ambient Temp Sensor), and CVT TR580 Control System (ATF Temp Sensor).

On the Impreza, these sensors let the ECU and control modules make smart decisions. The ECT tells the engine when to enrich fuel on cold starts and when to switch on the radiator fans. The IAT helps fine-tune fuelling and ignition for Aussie and Kiwi conditions, whether it’s a frosty morning in Dunedin or a scorching arvo in Brisbane. The ambient sensor feeds the climate control so the cabin temp stays comfy. The CVT’s fluid temperature reading protects the transmission, adjusting line pressure and shift strategy when things get hot.

They’re not a scheduled replacement item, but they’re worth a look during servicing. A few practical pointers:

• Scan live data: Compare ECT and IAT readings to actual conditions (cold engine should read close to ambient). Odd values or slow warm-up traces hint at a failing sensor or wiring issue.
• Inspect connectors: Check for corrosion, brittle loom tape, or oil/coolant wicking into plugs.
• Cooling system care: Fresh Subaru-spec coolant and proper bleeding help the ECT sensor read accurately and keep fans cycling as intended.
• CVT caution: The ATF temperature sensor is typically integral to the valve body/harness. If it’s out of spec, diagnosis and replacement are specialist jobs, with fluid level setting and adaptation procedures required.

If a sensor does fail, replacement is usually straightforward for the ECT and ambient units. Always follow the service manual torque specs and sealing steps. For the ECT, expect some coolant loss and be ready to top up and bleed. After any sensor work, clear fault codes and verify readings on a test drive. Treat them well and these little thermometers will keep the Impreza running sweet for hundreds of thousands of kilometres.

Popular questions

Where are the main temperature sensors on a 2020 Subaru Impreza?
The ECT sensor threads into the engine’s coolant passage near the thermostat area, the IAT is built into the MAF housing in the intake duct, the ambient temperature sensor sits ahead of the radiator (usually behind the grille), and the CVT’s ATF temp sensor is inside the transmission valve body.

Exact placement can vary slightly by trim, so a quick check of the Subaru service manual or a parts diagram helps pinpoint the connector locations before diving in.

What symptoms point to a failing coolant temperature sensor?
Common give-aways include hard cold starts, rich running, high fuel use, radiator fans stuck on or never coming on, a wandering temperature gauge, or an illuminated check engine light with ECT-related codes.

If live data shows an implausible coolant temperature (e.g., 130°C on a cold start), or the reading jumps around with a wiggle of the connector, the sensor or wiring likely needs attention.

Do temperature sensors need routine replacement?
No, they’re replaced on condition. During regular servicing, a technician will typically scan and sanity-check temperature readings, inspect connectors, and ensure the cooling system and CVT fluid are healthy.

Proactive replacement is usually only considered when there’s confirmed drift, a fault code, or physical damage. Using quality parts and correct installation helps avoid repeat issues.