Parts for your 2000 Subaru Forester-Temperature sensors

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

Based on the Subaru Factory Service Manual for the MY2000 Forester (SF), the Subaru wiring diagrams for this generation, and Subaru parts catalogues used by dealers, the 2000 Forester absolutely uses multiple temperature sensors. These include an engine coolant temperature (ECT) sensor feeding the engine control unit (ECU), an intake air temperature (IAT) sensor, an automatic transmission fluid (ATF) temperature sensor on 4EAT models, and temperature sensors used by the HVAC system. So “temperature-sensors” are not only relevant to the 2000 Forester—they’re essential to how it runs and keeps its cool.

The ECT sensor is the big player for drivability. It tells the ECU how warm the engine is so fuelling, ignition timing, idle speed and radiator fan control all behave properly from cold start through to highway cruising. The IAT sensor helps the ECU correct for hot or cold intake air, improving economy and throttle response. On 4EAT autos, the internal ATF temp sensor protects the transmission by altering shift strategy when fluid gets hot. Climate-control sensors simply keep the cabin comfy.

• Engine Coolant Temperature (ECT): ECU strategy, fan control, gauge data.
• Intake Air Temperature (IAT): fuelling trims and spark timing.
• ATF Temperature (4EAT): shift quality and transmission protection.
• HVAC/ambient/evaporator sensors: air-con performance and defogging.

There’s no fixed replacement interval for the ECT or IAT sensors, they’re serviced on condition. During routine servicing, a quick scan-tool check is gold: with a stone-cold engine, the ECT and IAT readings should sit close to ambient. Under the bonnet, check connectors for green corrosion, brittle wiring and coolant leaks near the ECT. Follow the factory coolant service schedule to keep sensor tips clean and readings accurate.

• Common signs of a crook ECT/IAT: hard cold starts, high idle, rich running, lousy fuel economy, cooling fans running constantly, temp gauge acting odd, or OBD-II codes P0115–P0119/P0112–P0113.

Replacing the ECT is straightforward for a competent DIYer: let it cool completely, relieve pressure, disconnect the two-pin plug, swap the sensor (use the correct sealing washer/O-ring), and top up with the right coolant mix. Bleed air carefully to avoid hot spots. Don’t overtighten—use the factory torque spec. Stick with quality OEM-equivalent parts, cheapies can read a few degrees off and cause headaches. On 4EAT models, the ATF temp sensor is internal and not a routine service item—diagnose before any big transmission work.

Where is the engine coolant temperature (ECT) sensor on a 2000 Subaru Forester?
On most 2000 Forester SF models, the ECT sensor sits on the coolant crossover passage at the top of the engine, under the intake manifold area, with a two‑pin connector. It’s near the thermostat housing/front of the block—visible once the intake ducting is out of the way.

Does a 2000 Forester have more than one temperature sensor?
Yes. There’s at least the ECT for the ECU, plus an IAT. Auto (4EAT) models include an ATF temp sensor. The cluster usually gets coolant temperature data via the ECU, some early or region-specific builds may also have a separate one‑wire sender for the dash gauge.

What fault codes point to a bad ECT or IAT sensor?
For ECT: P0115 (circuit fault), P0116 (range/performance), P0117 (low input), P0118 (high input), P0119 (intermittent). For IAT: P0112 (low input) and P0113 (high input). If these show up, check wiring and connectors first, then the sensor.