General Thinking of Building a Very Basic 1G OBD1 Diagnostic Scan Tool

[XC92]

That's 12v coming out the diagnostic connector. Luckily in this case a voltage divider should suffice as a solution.

I think that some Arduinos can handle 12V, and even if not like you said a simple voltage divider should work. That's for board power. The digital Arduino port reading the OBD1 12V signal would require one as well. But very basic stuff.

When I get around to building this I'll post everything in case anyone's interested.

 

[Jane Hacker]

No power off the diag connector: https://www.dsmtuners.com/threads/need-the-wiring-of-obd1-plug.348904/post-152673037
I've seen a spade connector to the fuse box as a solution. Inline fastblow fuse with that method obviously.

 

[XC92]

A 9V battery would also work, since most people won't need this to be connected for long. A real scanner is another matter.

 

[Jane Hacker]

Check this out! I just randomly stumbled upon it: https://www.prusaprinters.org/prints/89005-1st-gen-dsm-eagle-talon-diagnostic-connector A 3D printable diagnostic plug!

 

[XC92]

Thanks. I don't have a 3D printer but I assume that one can order a 3D part from companies that do this, like a 3D Kinko's?

 

[steve]

This is still the simplest and cheapest solution for just reading out the 1G ECU fault codes.

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[XC92]

Heh, no doubt, but not as fun.

 

[steve]

I see this old post and have a question. I have a copy of fordiag from Tomáš Chvátal. Do you know what cable he uses to make the connection to his software (PC based)? I understand that it is proprietary does that mean he special built it to decode OBD1 from early 90's fords with eec iv?

As far as I can tell Fordiag is Ford specific. Back in the OBD1 day and earlier there wasn't much standardization on the diagnostic interfaces so many were brand specific.

The only cable I found for Fordiag was on his Czech site and OBD2 so I don't know how it might relate to a Mitsubishi OBD1 cable.