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OBD-II On-Board Diagnostics

See Wikipedia 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 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.

Toyota Yaris 1KR-FE Engine, 998 cc, 51 kW (year 2006)

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.

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

tecnica/motori/obd-ii.txt · Last modified: 2018/08/04 07:33 by niccolo