Parts for your 2020 Subaru Legacy-Temperature sensors

2020 Subaru Legacy temperature-sensors

Temperature sensors are absolutely fitted and relevant on the 2020 Subaru Legacy. This is confirmed in Subaru’s factory service information for the 2020 Legacy/Outback platform, which details the Engine Coolant Temperature (ECT) sensor and Intake Air Temperature (IAT) sensor in the Engine Diagnostics section, the Ambient and Cabin temperature sensors in the HVAC section, and the Automatic Transmission Fluid (ATF) temperature sensor within the Lineartronic CVT control documentation (Subaru Service Manual/Technical Information System). Subaru diagnostic references also list DTC ranges for these sensors, including P0115–P0119 (ECT), P0110–P0114 (IAT), and P0711–P0713 (ATF temp), further verifying their use.

On a 2020 Subaru Legacy, temperature sensors keep the brains of the car (the ECU and TCM) in the loop so it can run sweet as under the bonnet and in the cabin. The ECT sensor tracks coolant temp so the ECU can set the right fuelling, ignition timing, idle speed and radiator fan operation. The IAT sensor helps with air–fuel mix, particularly on cold starts or hot days. The ambient and cabin sensors let the climate control hold the temp you’ve set, while the CVT’s internal fluid temperature sensor protects the transmission from heat stress and adjusts shift logic to stay smooth.

They’re solid-state parts and don’t have a set replacement interval, but like any piece of kit, age, heat and corrosion can have a go at them. Look for hard starting, rough idle, poor fuel economy, a stuck-on radiator fan, a dead outside temp reading, odd climate behaviour, limp mode, or a lit check engine light. A quick scan with an OBD tool to see live temperature data is the best first step. Compare readings to actual engine and ambient conditions—if the numbers are way off, the sensor or its wiring may be the culprit.

• Common sensors on a 2020 Legacy:
  • Engine Coolant Temperature (ECT)
  • Intake Air Temperature (IAT, often integrated with the MAF on some trims)
  • Ambient and cabin temperature (HVAC)
  • CVT transmission fluid temperature (internal to the unit)

• Service tips:
  • For ECT: replace only when testing confirms a fault, use a new seal, don’t overtighten, and bleed the cooling system properly.
  • For IAT: if it’s part of the MAF, clean with proper MAF cleaner—never harsh solvents.
  • For ambient/cabin sensors: check for debris, broken clips, or weather damage near the front bumper/grille.
  • For CVT temp issues: the sensor is internal, diagnosis first, then specialist transmission service if needed.
  • Always inspect connectors and earths—many “sensor” faults are actually wiring or plug problems.

Stick with quality OEM or reputable aftermarket parts, clear any DTCs after the fix, and take a decent test drive to confirm stable temperatures and proper fan and shift behaviour. Done right, these sensors quietly keep the Legacy running efficiently for heaps of kilometres.

FAQs

How do you know if the engine coolant temperature sensor is failing on a 2020 Legacy?
Common signs include hard cold starts, rich running, poor fuel economy, radiator fans running constantly, or a check engine light with codes like P0115–P0119. Use a scan tool to compare live ECT data to the actual engine temperature, if it’s reading wildly cold or hot when it shouldn’t, it’s suspect.

Do temperature sensors need regular servicing, or only replacement?
They’re maintenance-free components—no routine servicing. Inspect connectors during scheduled services, keep the cooling system healthy, and clean the MAF/IAT correctly if required. Replace a sensor only after proper diagnosis confirms it’s faulty.

Can you drive with a faulty temperature sensor?
It’ll usually run, but it’s not a great idea. A bad ECT or IAT can cause poor drivability and higher fuel use, and a dodgy CVT temp reading can trigger protective modes. Continued driving risks overheating or transmission damage—diagnose and fix promptly.