Parts for your 2014 Subaru Forester-Temperature sensors

2014 Subaru Forester temperature sensors – what they do and how to look after them

Temperature sensors are very much used on the 2014 Subaru Forester (SJ). Technical documentation such as the Subaru factory service manual for the 2014 Forester (engine control, HVAC and CVT sections), Subaru parts catalogues, and standard OBD‑II telemetry (SAE J1979) confirm multiple temperature inputs: an engine coolant temperature (ECT) sensor, an intake air temperature (IAT) sensor integrated with the MAF, an ambient/outside air temp sensor for HVAC and the dash display, an A/C evaporator temperature sensor, and a CVT fluid temperature sensor monitored by the transmission control module. These are all critical to how the Forester starts, runs, cools, shifts and keeps you comfy.

On this model, the ECT sensor is the engine’s main thermal reference. The ECU uses it to set cold‑start fuelling, ignition timing, idle speed and to command the radiator fans. If it reads wrong, expect hard starts, rich running, poor economy and over‑ or under‑cooling. The IAT (inside the MAF) helps fine‑tune fuelling and spark based on incoming air density, improving drivability across Aussie and Kiwi climates.

The cabin side isn’t left out. The ambient temp sensor feeds the outside temperature display and helps the HVAC decide how hard to work, while the evaporator temp sensor prevents the A/C core from icing up. In CVT models, fluid temperature is monitored so the TCM can protect the transmission, adjust shift behaviour and manage thermal load when towing or climbing.

Service tips that actually help:

• ECT sensor: Not a routine replacement item, but replace if it’s out of spec or flagged by diagnostics (think DTCs like P0117/P0118). Any time the sensor is removed, fit a new seal, use correct coolant, and bleed the system properly to avoid air pockets that can skew readings.
• IAT/MAF: If airflow readings seem off or trims are wonky, try cleaning the MAF with a proper MAF cleaner. Don’t touch the element. Replace the unit if values remain unstable.
• Ambient and evaporator sensors: Inspect connectors and mounting. If the outside temp reads silly values or A/C cycles oddly, test resistance against the service manual chart and replace if outside spec.
• CVT fluid temp sensing: It’s typically internal, if the TCM logs temperature‑related faults, further diagnosis may point to wiring, connectors or internal components. Keep CVT fluid in good nick at the recommended intervals to maintain accurate temperature control.

Practical signs of trouble include the temp gauge misbehaving, cooling fans running flat‑out, rough cold starts, high fuel use, or erratic A/C performance. A scan tool that shows live ECT/IAT/ambient data is the quickest way to confirm what the sensors are actually telling the car.

Popular questions

How do you know a temperature sensor is failing on a 2014 Forester?
Common hints include hard cold starts, the cooling fans running constantly, a temperature gauge that jumps around, or poor fuel economy. A scan will often reveal codes such as P0117/P0118 (ECT), P0113 (IAT) or P0073 (ambient). Checking live data against the actual engine temperature or ambient conditions is the best first step.

Do temperature sensors need routine replacement?
No set interval. They’re “as‑needed” parts. Keep the cooling system healthy, maintain good electrical connections, and service the MAF carefully. Replace a sensor only if it’s out of spec, damaged, or flagged by diagnostics.

Can the intake air temperature sensor be cleaned instead of replaced?
Yes—because it’s part of the MAF. Use a dedicated MAF cleaner and gentle technique. If readings are still off after cleaning and wiring checks, replacement of the MAF assembly may be required.