====== OBD-II On-Board Diagnostics ======

See Wikipedia **[[wp>On-board_diagnostics]]**.

^ ECU      | Eengine Control Unit: controls a series of actuators on an internal combustion engine to ensure optimal engine performance.  |
^ 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      | [[wp>OBD-II_PIDs|On-board diagnostics Parameter IDs]], codes used to request data from a vehicle.  |
^ Service  | OBD-II standard (SAE J1979) defines several //[[wp>On-board_diagnostics#Diagnostic_services|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/[[wp>Check_engine_light|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.  |
===== Toyota Yaris 1KR-FE Engine, 998 cc, 51 kW (year 2006) =====

We tried the **iLC OBD2** adapter (WiFi version) along with the Android app **[[https://play.google.com/store/apps/details?id=org.prowl.torquefree|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.

==== OBD-II Available Sensors (PIDs) ====

  * Engine Coolant Temperature(°C)
  * Intake Air Temperature(°C)
  * Intake Manifold Pressure(kPa)
  * Timing Advance(°)
  * Fuel Trim Bank 1 Short Term(%)
  * Fuel trim bank 1 sensor 1(%)
  * O2 Volts Bank 1 sensor 1(V)
  * O2 Volts Bank 1 sensor 2(V)

==== OBD-II Unavailable Sensors (PIDs) ====

  * Fuel pressure(kPa)
  * Fuel trim bank 1 sensor 2(%)
  * Fuel trim bank 1 sensor 3(%)
  * Fuel trim bank 1 sensor 4(%)
  * Fuel trim bank 2 sensor 1(%)
  * Mass Air Flow Rate(g/s)
  * O2 Sensor1 Equivalence Ratio
  * O2 Volts Bank 2 sensor 1(V)

===== Web Reference =====

  * **[[wp>OBD-II PIDs]]**
  * **[[https://mechanics.stackexchange.com/questions/17537/how-is-engine-load-determined|How is engine load determined?]]**
  * **[[https://www.obd-codes.com/faq/fuel-trims.php|What are fuel trims?]]**
  * **[[http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info|Fuel Trim Info]]**
  * **[[https://www.freeasestudyguides.com/fuel-trim-adaptive-learning.html|Short Term Long Term Fuel Trim Explained]]**
  * **[[http://ricksfreeautorepairadvice.com/open-loop-versus-closed-loop/|Open loop versus closed loop]]**
  * **[[http://www.underhoodservice.com/tech-feature-detecting-misfires-in-obd-ii-engines/|Tech Feature: Detecting Misfires in OBD II Engines]]**