What causes the PO117 Code?

The PO117 code indicates a problem with the engine coolant temperature (ECT) sensor, specifically that the sensor is reading a temperature that is lower than expected, typically below -40°C (-40°F). This can be caused by a faulty ECT sensor, poor electrical connections, damaged wiring, or issues with the engine's cooling system, such as low coolant levels. If not addressed, this code can lead to poor engine performance and increased emissions. It's essential to diagnose and fix the underlying issue to prevent further complications.