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OBD II Plug and Software

Is the OBD II wire a common computer plug? Can I say harvest a SCSI cable or other and use that?

Where does one find reliable free software to analyze the OBD II data?

The OBD 2 plug has its own standard and design.

Some time back, I had a crazy notion to develop my own diagnostic tool set for OBDII. It didn’t take long to abandon that idea when I discovered that there were 3 different hardware protocols as well as a number of (perhaps 5) software protocols that had to be implemented in order to work with all variants of the standard.

The hardware chips are available and you can even locate designs on-line for that aspect.

I was fortunate enough to get a copy of the software protocols and it was like 200 double sided pages long on 11x17 paper. Not overtly difficult to implement with the exception of the vast number of commands and responses required. Then you’ll need to build an interpretation table for the diagnostic codes, including the manufacturer-specific ones, assuming you can even find all of them without purchasing an existing scanner.

I have never run across any free versions of software. I did locate one guy’s version of the hardware interface layer but the upper level software that encodes/decodes the protocol, issues commands and interprets the responses was not available unless you paid for the priviledge.

I ended up buying an EQUUS scanner for $120 and that was the end of that notion. YMMV.

You can’t plug it directly in. I have a OBD II reader that plugs into a laptop rs-232 port. The OBD II reader is basically a serial data converter. Then I have software installed on my laptop that actually reads the OBD II. YOu just can’t plug a cable directly into the OBD II and expect to be able to read it. There are newer ones that connect to a USB port.

This link contains a schematic for building your own serial data converter.

Here’s a link for a cable and software for your PC to read the OBD II.

You can analyze OBD2 using your brain and a factory or equalivent manual. Really alot can be done with these tools.Are you trying to look at freeze frame data? Or pull codes with a PC? Just get a scanner and use your time becomming proficent with it. Or perhaps this is just a hobby shop expermint. I enjoy that kind of challenge also

oldschool — re: “Just get a scanner and become proficient with it…”

i want to read the codes in order to make what repairs i can with the family cars (Honda 2000and Toyota 2003) and also to minimize expense when turning to the pros. Can you recommend a particular scanner that doesn’t require hooking up to a PC? (Using the brain is good — plus the software I’ve seen is all for PC and I have a Mac) Thanks!