Parts for your 2006 Subaru Forester-Temperature sensors

2006 Subaru Forester temperature sensors — what they do and how to keep them sweet

Temperature sensors are absolutely relevant and fitted to the 2006 Subaru Forester (SG). Technical sources including the Subaru Factory Service Manual for the 2006 Forester (SG, EJ25), the Subaru Technical Information System (STIS), and standard OBD‑II diagnostics used with the Subaru Select Monitor all document multiple temperature inputs: the engine coolant temperature (ECT) sensor, intake air temperature (IAT), ambient air temperature for HVAC, and transmission fluid temperature on 4EAT models. These sensors feed the engine and climate control computers to manage fuelling, ignition timing, cooling fans, A/C performance, and shift strategy, with related fault codes such as P0115–P0119 (ECT) and P0110 (IAT) called out in the service literature.

On this Forester, the ECT sensor is the big player. It tells the engine control module how hot the engine is so it can adjust cold-start enrichment, idle speed, timing, and when to kick the radiator fans on. Many 2006 Foresters also read IAT (often integrated in the MAF housing) to fine-tune fuelling as air density changes. The climate system uses an ambient sensor to display outside temp and to keep the cabin comfy, while auto transmissions monitor fluid temperature to protect the gearbox and tidy up shift feel.

As part of routine servicing, these sensors don’t need constant replacement, but they do need a bit of love:

• Keep the cooling system healthy: correct coolant mix, no leaks, clean connectors near the thermostat and coolant crossover area.
• If the Check Engine light’s on with codes like P0115, P0117, P0118 or the fans behave oddly, confirm with scan tool live data before swapping parts.
• Inspect plugs and wiring for corrosion or broken clips — heat and age under the bonnet can be rough on plastics.

Replacement of the ECT sensor is straightforward for a competent home mechanic, but patience helps. Work on a cold engine, relieve pressure carefully, and catch any coolant. The sensor threads usually seal without tape, follow the workshop manual for torque and any sealant call-outs. After refitting, top up with the correct coolant, bleed air from the system (heater on, let the fans cycle), clear codes and verify with a scan tool that temperatures look realistic at cold start and at operating temp. Sticking to OEM-quality sensors avoids weird readings that cheap copies sometimes cause.

When temperature sensors are behaving, the Forester starts cleanly on a frosty morning, holds a steady idle, runs efficiently, and keeps the fans and A/C doing their job without dramas — exactly how owners like it.

Where is the coolant temperature sensor on a 2006 Forester?

It sits on the engine’s coolant crossover passage near the top/front of the engine, close to the thermostat area. It’s accessible from above with basic hand tools, though some intake ducting may need to be moved for room.

Does the cooling system need bleeding after replacing the ECT sensor?

Yes. Any time the cooling circuit is opened, refill with the correct coolant and bleed air. A spill-free funnel helps. Run the engine with the heater on, allow the fans to cycle, and top up the overflow bottle after a short drive once it cools.

Can a dodgy temperature sensor cause poor fuel economy or rough idle?

It can. If the ECT or IAT reads colder than reality, the ECU enriches the mixture and can hold a higher idle, burning extra petrol. Expect hard cold starts, rich smell, or erratic fan operation, and often a fault code to match.