Author Topic: What to do if your G40 doesn't have diagnostic wiring  (Read 4382 times)

Offline hayesey

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What to do if your G40 doesn't have diagnostic wiring
« on: February 10, 2009, 01:54:57 pm »
For some reason some G40s randomly don't have the 2x2 diagnostic ports fitted to them.  The wiring for them simply isn't there.  This doesn't mean you can't connect up diagnostic equipment, just that you will have to do some wiring first.

The 2x2 connectors have two wires on each one so four wires in total.  On a G40 only three of these wires do anything.  Two of them are simply 12v and earth so can be connected to a 12v source in the car (directly to the battery if you wanted).  The third wire is the important one which connects to the ECU which is used for the actual diagnostic signals.

Here is a 2x2 connector pin-out diagram I found:

The signal wire is the "K-Line", this needs to connect up to pin20 on the ECU connector.  Note, in G40s with the correct wiring, the wires aren't actually coloured yellow & blue, they are yellow/white (k-line) and solid yellow (l-line). 

You can ignore the L-Line wire, it shouldn't need earthing.

Also note, most VAGCOM leads will have an ODB connector on them, you'll need an ODB to 2x2 adaptor which are readily available from people like Ross-Tech or also on ebay.  As far as I'm aware the adaptor is more than just a wiring adaptor so I don't think you can just run these wires directly into certain ports of the ODB connector.  Although I stand to be corrected on that if anyone knows better.
« Last Edit: February 10, 2009, 01:57:13 pm by hayesey »

Offline Nick_S

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Re: What to do if your G40 doesn't have diagnostic wiring
« Reply #1 on: February 10, 2009, 08:18:37 pm »
Good info.
I just got some donor plugs from a mk3 down the scrappers and then traced the pins to the internal loom. Here is the engine bay side plug from a photo in Max Crox's build thread on CP.