OBd2 Standards and Terms

OBD2 standard
OBD2 (or OBDII) defines a communications protocol and a standard connecter to acquire data from passenger cars. It was required by U.S. EPA on all gasoline powered cars and light duty trucks manufactured for the U.S. after 1996 to help monitor/inspect vehicle emissions. Canada required it after 1998, and a European standard (EOBD) is also enforced.

OBD2 electrical interfaces
The OBD2 standard allows for multiple electrical interfaces, which complicates the hardware used to interface with the vehicle.  Here is a brief summary of the most popular electrical interfaces:

  • ISO15765 (CAN) – Controller Area Network, a new higher speed interface, just now being implemented (This protocol is currently not supported by any ELM32x or by our software)
  • ISO9141-2 used mostly by Chrysler and the European/Asian imports
  • ISO14230, or KWP2000 (Keyword Protocol) shares the electrical portion of ISO9141 standard, but defines it’s own commands. (This protocol is currently not supported by the ELM323 (ISO) or by our software)
  • PWM J1850-41.6 (41.6Khz Pulse Width Modulated) used mostly by Ford (supported by the ELM320 chip)
  • VPW J1850-10.4 (10.4Khz Variable Pulse Width) used mostly by GM vehicles (supported by the ELM322 chip)

OBD2 Acronyms
Some additional terms you may run across in OBD2:

  • CTS – Coolant Temperature Sensor, pretty self-explanatory
  • DLC – Data Link Connecter, the standardized plug in the vehicle, a 16-pin trapezoidal connecter, often found under the driver side dash (U.S. EPA’s allowed DLC location GIF)
  • DTC – Diagnostic Trouble Codes, an alphanumeric code indicating a specific fault reported by the OBD system
  • ECM – Electronic Control Module, a vehicle computer
  • ECU – Electronic Control Unit, a vehicle computer
  • EGR – Exhaust Gas Recirculation, to recirculate unburnt volatiles in exhaust
  • HO2S – Heated Oxygen Sensor, refers to oxygen sensors in exhaust path looking for unburnt oxygen
  • ISO – International Standards Organization
  • KOEO – Key On Engine Off, describes some tests without engine running, but ignition on
  • KOER – Key On Engine Running, describes tests with engine running
  • MAF sensor – Mass Air Flow measures amount of air being drawn into intake
  • MAP sensor – Manifold Absolute Pressure, reads air pressure to adjust timing, fuel/air ratios
  • MIL – Malfunction Indicator Light, indicates a trouble code has been recorded. Also referred to as the Service Engine Soon light, the Check Engine light, idiot light, etc. Usually can only be reset by an OBD2 tool (even if the condition is no longer present), will automatically fail any emissions test if lit.
  • PCM – Programmable Control Module, a vehicle computer that can be reprogrammed/have values modified
  • PCV – Positive Crankcase Ventilation – recirculates unburnt volatiles escaping into crankcase
  • SAE – Society of Automotive Engineers
  • Scantool – an OBD2 tool
  • SIR – Supplemental Inflatable Restraint – airbag
  • Tap Test – Gently striking the ECU housing with fingers with engine running to check for intermittent connections
  • TPS – Throttle Position Sensor, monitors position of the accelerator pedal/throttle linkage
  • WOT – Wide Open Throttle, pedal to the metal

Good for You, Good for the Environment

How to get better gas mileage?

With today’s high gas prices, here are some tips from OBD2 blog.

Here are simple tips:

  1. Go Easy on the Pedals
  2. Slow Down
  3. Leave Extras at Home
  4. Use Cruise Control (When Appropriate)
  5. Turn off the Car, when idling at read lights
  6. Check Tire Pressure
  7. Replace Spark Plugs
  8. Check Alignment
  9. Fill Your Tank Early in the Morning – or Late at Night
  10. Purchase an OBD2 CAN Scanner,  very good to check the condition of the oxygen sensor O2. Replacing near faulty O2 sensors drastically improves gas mileage and performance.

Obd2 scan tool could make you save hundreds of dollars…..

Car Owners Can Save Hundreds of Dollars on Auto Repairs with a OBD2 scanner.

DIY, is the keyword here.

How ? You purchase a OBD2 Scan Tool  for under one hundred dollar.

Then by utilizing tips and information on online help, automotive forums and other tools. Example, you get a check engine light code (DTC) P0171 and P0174 on a Ford F-150, Some Mechanic tells you that is 100 % sure it’s the Oxygen sensor !!!

But, What it means is that the engine is running lean. There are many possible problems that may cause the air-fuel mixture to be lean: Defective or contaminated airflow sensor, intake vacuum leak, dirty fuel filter, etc. There are certain tests to be performed to find the exact cause of the problem. Common problems with Ford engines are defective airflow sensors and vacuum leaks.

So, replacing the O2 sensors for nothing may cost you up to $ 600. By using this simple and low cost obdii CAN scanner

You can save Hundreds and Hundreds Dollars. The internet is full of Forums dedicated to you our make of car and with valuable advice form users that did repair their our cars.

New exciting software on the market for advanced obd2 diagnostics


I found some new exciting software on the market for advanced obd2 diagnostics. With these programs you can read, erase and log :

anti-lock braking system (ABS OBDii)

supplementary restriant system (SRS OBD-ii)

advanced powertrain systems like electronic transmissions, CVT  (Auto OBD2)

Right now theses software packages are just available for Ford, GM and Mazda cars.

 Obd2 Enhanced Software Packages

ECU scanning has come from a long way since obd1 systems.