On-Board Diagnostics II (OBD II), which will be to be introduced into motorcycles in Europe and India, requires that the engine oil and cooling water temperatures be monitored in a rational manner. The rationality of the sensors for engine oil and coolant temperatures (TW sensors) is derived from the ability to detect failure modes such as offset or fixation of unintended output voltage in addition to circuit continuity checks such as sensor harness disconnection and short circuit.
The OBD II technology for 4-wheeled vehicles cannot be easily converted to motorcycles with their multiple cooling systems (air-cooled and water-cooled) and multiple heat dissipation structures (full fairings, naked structures, etc.). In previous studies, failures of the TW sensor were detected by estimating the water temperature with high accuracy based on the calorific value of the engine and the amount of heat dissipated. However, in studies considering the implementation of electronic control units (ECUs), it has been reported that such estimations are vulnerable to disturbance (especially from a heater or blower) because it was difficult to estimate water temperature based on accurate heat removal. In addition, since the motorcycle has a heat-dissipating structure that facilitates cooling, it is necessary to consider heat removal in any environment.
In this study, in order to detect a failure in the TW sensor, the temperature increase is estimated based on the amount of fuel injected during the engine operation and the temperature change characteristics of the TW sensor corresponding to the engine load, in the coldest environment in which the vehicle is used. The proposed method has a feature that it does not require re-correction of parameters for normal temperature or high temperature environments. Firstly, the parameters required to estimate an increase in temperature in the TW sensor during operation are discussed. In the preliminary test, in order to understand the detection characteristics for temperature increase of the TW sensor, an engine heating value test was conducted under a predetermined low-temperature environment during engine operation. Next, the detection performance in the simulation environment was confirmed using fault detection logic based on the above. This fault detection logic was implemented in an ECU, and vehicle tests were conducted under various temperature load conditions on a low-temperature chassis dynamometer to confirm the usefulness of the proposed method.