P0117 Subaru Forester
Engine Coolant Temperature Sensor Circuit Low · Powertrain Code · Medium · Repair: Easy
What is P0117?
The coolant temperature sensor is reading lower than expected — possible open circuit or faulty sensor.
When the Subaru Forester triggers code P0117 (engine coolant temperature sensor circuit low), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Subaru Forester.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Subaru Forester.
Common Causes on Subaru Forester
- Failed ECT sensor reading low voltage
- Short in ECT sensor wiring harness
- Corroded ECT sensor connector from coolant seep
- Ground circuit issue affecting ECT signal
Symptoms
- Check Engine Light on
- Radiator fans running constantly
- Gauge reads cold when engine is warm
- Rich fuel mixture and poor economy
Notes for Subaru Forester
On boxer engines, the ECT sensor location varies; consult the service manual for your specific model year.