OBD2 (OBDII) Explained

What is OBD, and what are its benefits?
OBD stands for "On-Board Diagnostics," a computer-based system built into modern vehicles. OBD monitors the performance of some of the engines' major components, including individual emission controls. The OBD system on a vehicle normally consists of one or more ECUs (Electronic Control Unit – basically a computer), a Malfunction Indicator Light (MIL), Diagnostic Link Connector (DLC), and the wiring that connect these different elements.  The system provides owners with an early warning of malfunctions by way of a dashboard "Check Engine" light (also known as a Malfunction Indicator Light or MIL, for short). By giving vehicle owners this early warning, OBD protects not only the environment but also consumers, identifying minor problems before they become major repair bills.

What is OBD2? 

OBD2 is the second generation of OBD. It is a set of standards issued by the SAE (Society of Automotive Engineers) and ISO (International Organization for Standardization).

OBD II was created to set a standard communication amongst all car manufacturers and to provide a fixed minimum requirement on emission data. 

OBD2 (also referred to as OBD2) uses a J1962 socket to allow interfacing with a diagnostic reader system – usually a PC based software/hardware or handheld device. 

Now while OBD2 has created a set of standards across manufacturers, different manufacturers have still chosen to use their own communication protocols within that system. Put simply, while still using the standard hardware set by OBDII and its data requirements, the communication between the OBD system within the vehicle and the scanning device varies. There are five different communication protocols to date. These are: 

J1850 PWM,  

J1850 VPW,  

ISO9141-2 ,  

ISO14230-4 (also known as Keyword Protocol 2000),  

ISO15765-4/SAE J2480 (also known as CAN and becoming the set standard amongst more manufacturers). 

How do I know what protocol my vehicle uses? 

One way is to look at your vehicle’s diagnostic port (the J1962 socket). If all the pins are not present you may be able to determine the protocol from the pins that are used. See the following diagram and list: 

Where can I find the OBD II diagnostic socket on my car? 

Within OBD II guidelines the diagnostic port should be situated within reach of the driver’s side seating position. Common locations are just under the steering wheel shroud or to the side of the centre console. Check your vehicle’s handbook for specific information.

Which Interface do I need? 

If you plan to use the tool with a single vehicle, you only need one interface. However, if you plan to use it on vehicles with different protocols, you need to buy multiple interfaces, depending on the number of protocols (up to four - ISO, VPW, PWM and CAN).

The ELM327 diagnostic reader we sell covers ALL the protocols in one unit!

ISO 

Interface using the ISO9141-2 and ISO14230-4 (KWP - Keyword Protocol 2000)  protocols used mostly in Chrysler Corporation, European, and Asian vehicles.

VPW 

VPW (Variable Pulse Width) scan tool supports the J1850 VPW protocol used mostly in General Motors vehicles.

PWM 

PWM (Pulse Width Modulation) is the J1850 PWM protocol used mostly in Ford Corporation vehicles and Mazda.

CAN 

ISO15765, also known as CAN (Controller Area Network). This protocol was introduced in 2004 model year vehicles and will eventually become the only protocol for legislated OBD. 

How do you know if your vehicle is OBD2 compatible? 

There are several ways.

1996 or later vehicle sold in the United States

United States legislation requires all cars and light trucks model year (MY) 1996 and newer to be OBD2 compliant.

2001 or later petrol vehicle sold in the European Union*

Commission Directive 70/220/EEC, Annex I:

8.1. Vehicles with positive-ignition engines
With effect from 1 January 2000 for new types and from 1 January 2001 for all types, vehicles of category M1, except vehicles the maximum mass of which exceeds 2500 kg, and vehicles of category N1 class I, must be fitted with an on-board diagnostic (OBD) system for emission control in accordance with Annex XI. [...]

* Referring to countries which were members of the EU in 2000.

2004 or newer model year diesel vehicle sold in the European Union**

Commission Directive 70/220/EEC, Annex I:

8.2. Vehicles with compression-ignition engines
Vehicles of category M1, except
- vehicles designed to carry more than six occupants including the driver,
- vehicles whose maximum mass exceeds 2500 kg,
from 1 January 2003 for new types and from 1 January 2004 for all types, must be fitted with an on-board diagnostic (OBD) system for emission control in accordance with Annex XI.

** Referring to countries which were members of the EU in 2003.

Other vehicles

If your vehicle does not fall into any of the above categories, look under the bonnet and try to locate a label that states that the vehicle was designed to comply with OBD2 legislation.

The following lettering can mean OBD2 compliance:

• OBD II (California ARB)
• EOBD (European OBD)
• JOBD (Japanese OBD)

You may also consult your vehicle's owner's manual and perhaps contact your local dealer. If the vehicle is not OBD2 compliant, you cannot use a generic OBD2 scan tool to obtain diagnostic information from your vehicle.

All Vehicles with D-shaped 16 pin connectors are OBD2?

Having a D-shaped 16 pin connector doesn't automatically mean the vehicle is OBD2 compatible. Many European and Asian manufacturers equipped their vehicles with D-shaped 16-pin connectors long before OBD2 came to be. 

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