Parts for your 2000 Subaru Legacy-Temperature sensors

2000 Subaru Legacy temperature-sensors: what they do and how to look after them

Temperature sensors are absolutely fitted to the 2000 Subaru Legacy. The Subaru Factory Service Manual for the 2000MY Legacy/Outback (BE/BH) lists several: the Engine Coolant Temperature (ECT) sensor feeding the engine control module, a separate coolant temperature sender for the dash gauge on some trims, an Intake Air Temperature (IAT) element (integrated with the airflow meter on many EJ-series engines), and—on autos—a transmission fluid temperature sensor. Wiring diagrams and the Engine Diagnostics section in the Subaru manual, along with Subaru parts catalogues for part numbers such as the ECT sensor, confirm their presence and function.

On this model, the ECT sensor is the big player for everyday running. Under the bonnet, it monitors coolant temperature so the ECU can sort cold starts, fuel delivery, ignition timing, idle speed, and radiator fan control. When it’s reading right, the Legacy warms up cleanly, holds steady temps in Kiwi and Aussie conditions, and keeps fuel economy in check. The IAT trims fuelling as air density changes, while the dash sender simply moves the gauge needle so the driver can keep an eye on things.

Because they’re thermistors living in a hot, wet environment, these sensors can age. Typical clues include hard cold starts, an over-rich smell, higher-than-usual fuel use, lazy idle, radiator fans that run when they shouldn’t, or a dead or dodgy temperature gauge. OBD-II fault codes like P0115–P0119 (ECT) or P0110 (IAT) are common flags in scan data.

They’re not a scheduled replacement item, but they’re worth checking during regular servicing, especially if the cooling system has recently been worked on. Good practice includes:

• Inspecting the connector and harness for green corrosion, brittle insulation, or oil/coolant wicking.
• Verifying live data with a scan tool: cold readings should be close to ambient, then climb smoothly to roughly 85–95°C at operating temp.
• Ensuring cooling fans cut in and out consistently, and the gauge sits where it normally does.

Replacing the ECT sensor is straightforward for a competent DIYer. Work on a cold engine, relieve any system pressure, and be ready to catch a small coolant dribble. The sensor lives on the coolant crossover near the intake, unplug, swap like-for-like, use the correct sealant if specified by the manufacturer, and tighten to the factory torque. Top up with the correct Subaru-approved coolant, run the heater on hot, and burp the system so there’s no trapped air. If in doubt, a trusted workshop can test, supply, and fit the right part and clear any fault codes so the Legacy’s ECU sees proper temps again.

Popular questions about 2000 Subaru Legacy temperature-sensors

Where is the coolant temperature sensor located on a 2000 Legacy?
On most EJ engines in this year, the ECT sensor threads into the coolant crossover pipe near the intake manifold, close to the thermostat housing area. It has a two-pin plug. Some models also have a separate one-wire sender nearby for the dash gauge. Access is typically from the top with basic hand tools.

Can you keep driving with a faulty coolant temp sensor?
It’ll usually run, but it’s not a great idea. A bad reading can make the ECU dump extra fuel, wash cylinder bores, foul plugs, trigger constant fan operation, and hide real overheating. Short trips home are one thing, for daily use, fix it promptly to avoid poor economy and potential engine damage.

Do you need to bleed the cooling system after sensor replacement?
Yes—any time the system is opened. Refill with the correct coolant mix, set the heater to hot, run the engine, squeeze the upper hose to purge air, and top up the radiator and overflow bottle. Watch scan-tool temps and the dash gauge to confirm stable operation with no air pockets.