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People often write asking where they can get more OBD information, or for help in making their circuits, etc. The sections shown at the left provide answers to most of the common questions that we receive.

Perhaps the most popular question of all is:

What OBD protocol does my car use?

There is a chance that your car may not use any. Not all vehicles use standard OBD (On Board Diagnostics) protocols, so do not be surprised if yours does not. If your car is older, or from a country that does not require OBD, then your car will likely not respond to OBD requests for data.

Some regions passed laws requiring OBDII compliance many years ago, while others have only recently required it. It is difficult to come up with a truly accurate list, but here are the approximate Model Years for when laws came into effect for light duty vehicles:

Cars and light duty trucks that were manufactured for sale in these regions (ie not imported), will likely work well with our products. If your vehicle is older than this, it is likely not OBDII compliant, even if it uses a similar looking connector. Note that large trucks and busses generally have different requirements, and use different protocols (usually SAE J1708 or SAE J1939). We are not referring to them in this discussion.

Vehicles that comply with the OBDII standards will have a data connector within about one meter of the driver's position. Check the owner's manual for information on its location as newer manuals often provide this information. In most cases, it will be in plain sight at the bottom of the dashboard, but occasionally it will have a cover that needs to be removed, or moved sideways (there are a few vehicles that have the connector behind a panel in the centre of the dashboard).

The OBD connector is officially called an SAE J1962 Diagnostic Connector, but is also known by DLC, OBD Port, or OBD connector. It has positions for 16 pins, and looks like this:

J1962 connector

Be careful, as many vehicles that do not comply with the OBDII standards do occasionally use the J1962 type connector for data, but do not use a standard OBDII protocol for data exchange. These may appear as if they should work, but they will not (and you may cause damage to the circuits if you connect the wrong voltages to them).

Locate this connector in your vehicle and determine if wires are in pins 2, 6, 7, 10, 14 or 15. Once you know which pins are used and which are not, then determine which standard applies to you using the following table:

Pin 2Pin 6Pin 7Pin 10Pin 14Pin 15StandardUse
must have--must have--J1850 PWMELM320
or
ELM327
must have-----J1850 VPWELM322
or
ELM327
--must have--may have*ISO9141-2
or
ISO14230-4
ELM323
or
ELM327
-must have--must have-ISO15765-4
(CAN)
ELM327
or
ELM329

* not all ISO9141 or ISO14230 vehicles use pin 15 (the 'L' line)

The above should be considered a good guideline. The presence or absence of wires in the connector is not an absolute indication though, as only your vehicle manufacturer can say for sure which standards the vehicle was built to.

New cars (2008+) now generally use the faster ISO15765 (CAN) protocol, but older vehicles might have used one of several. The protocol used by a particular manufacturer was generally consistent, but is not guaranteed to be so (for example, Chrysler started using ISO9141 and switched to J1850 around 2000). Typically, you will find the following standards usage for older vehicles:

ManufacturerJ1850
PWM
(ELM320)
J1850
VPW
(ELM322)
ISO9141
ISO14230
(ELM323)
ISO15765
CAN
(ELM327 or
ELM329)
Acura  X 
Chrysler XX 
FordX   
General Motors X  
Honda  X 
Saturn X  
Subaru  X 
Suzuki  X 
Toyota  X 
Volkswagen  X 

Actually, beginning with the 2005 model year, some North American vehicles did begin using the ISO 15765-4 (CAN) interface standard, so maybe we should have put some 'X's in the last column. The above should be a good starting point for you, though.

Beginning with the 2008 model year, all North American vehicles were required to use ISO 15765-4 (CAN).





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