A system and method for detection of coking in a fuel. The system including a fuel system for delivery of fuel, a fuel contamination sensor having a contamination detection sensor with input and output transducers immersed in the fuel, a controller in operable communication with the fuel contamination sensor, the controller configured to execute a method for detection of coking in fuel. The method including generating an excitation signal for the contamination detection sensor, receiving at a controller operably connected to the contamination detection sensor, a sensor output signal from the output transducer, comparing the sensor output signal with the excitation signal, diagnosing a condition of the fuel based on a the comparing, and indicating a condition of coking based on the diagnosing. The system also includes an enunciator to indicate the detection of coking in the fuel.