as well as the actual data communications, all how it would be accessed, presented, listed, was sorted out right down to the connector type which must be used and where it could be fitted, even the service reminder light was a part of this. In fact 3 standards were included at that time 2 called J1850 to appease the large influential motor corporates that had their own comms standards that they would rather go public with that change their cars, the other was a standard ISO 9141 that Europe was adopting. He looked into it and found that modern cars had intelligent computer systems controlling their emissions, but due to tight security and anti access measures only the manufacturer/ dealers could access these and check that the engines were were running right and producing low pollution levels, they had a monopoly, charged what they wanted and people with cars were not wanting to go to dealers and get their cars checked / fixed.Īngered, the guy said right we design a communications standard that will be openly published so any half intelligent software company can read how to access usin this communications standard. I will try my best to break it down and explain it simplistically.Īt some point in time, some Californian official cycled to work and got a bit miffed about the pollution pouring from cars. Wishful thinking or deception on the part of unscrupulous scan tool vendors certainly does not help to clarify this, and unless you study it extensively which i must as part of my job, it is confusing. Sadly however many people are confused about OBD EOBD and they just do not really fully understand just what the term OBD actually means.

There are also a large and growing number of software companies providing software that uses one of the elm interfaces, usually in the form of a limited Demo and then purchasable extra features or whatever I have myself purchased a number of full kits for less money than i buy OBD plugs for.

Nowadays ready built interfaces can be purchased all over the place for very little money, helped no doubt by the fact that the chip has a few Chinese clones in circulation. It is very cheap, and has been widely adopted as the hardware of choice for a number of companies writing diagnostic software. It has a simplified Ascii command set to achieve OBDII communications on a vehcile via a PC's standard RS232 port and all details of the circuit required to construct a finished interface based on it are supplied in an extensive manual.

The Elm 327 is a small Micro controller chip designed to act as an OBD to RS232 interpreter, for hobbyists and experimenters.

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