See Wikipedia On-board_diagnostics.
| ECU | Eengine Control Unit: controls a series of actuators on an internal combustion engine to ensure optimal engine performance. |
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| DTC | Diagnostic Trouble Code: 4-digits, preceded by a letter: P for engine and transmission (powertrain), B for body, C for chassis, and U for network, |
| PID | On-board diagnostics Parameter IDs, codes used to request data from a vehicle. |
| Service | OBD-II standard (SAE J1979) defines several services (or modes) used to communicate with the ECU. There is a service to request PIDs data, a service to clear DTC, etc. |
| MIL/CEL | Malfunction Indicator Lamp/Check Engine Light, typically has amber color. When the MIL is lit, the engine control unit stores a fault code DTC related to the malfunction. |
| Freeze Frame | When the check engine light turn on, the ECU determines the error based on several engine operating conditions and stores it in what’s called a OBDII freeze frame. The data stored in Freeze Frame is usually recorded when a system fails the first time for two consecutive trip faults. Freeze Frame data will only be overwritten by a different fault with a higher priority. |
| Fuel trim | Fuel trim is an adaptive strategy that adjusts fuel injector pulse width (open time) to adapt to wear, defects, or changes in the system. There is a short term fuel trim STFT and a long term fuel trim LTFT strategy. |
| Closed loop mode | In closed loop mode the vehicle is adjusting air/fuel mixtures based on the real time results it’s getting from the oxygen sensors. Engine stays in open loop for a few minutes, until oxygen sensor reaches its working temperature, etc. |
| Misfire | Most engine control systems with OBD II monitor the speed of the crankshaft between cylinder firings to detect misfires. The change in rotational velocity indicates a misfire must have occurred. |
| Bank 1 and 2 | There are a number of OBD-II trouble codes that refer to either Bank 1 or Bank 2. Bank 1 refers to the side of the engine that has the #1 cylinder, Bank 2 is the opposite side of the engine. |
We tried the iLC OBD2 adapter (WiFi version) along with the Android app Torque Lite (OBD2 & Car) on a 2006 Toyota Yaris 1.0 XP9 KSP90G, equipped with the 1KR-FE engine. As expected some sensors are available, some others are not; here a partial list we compiled.