348 gts misfire and pulling 2.7 codes

Gentlemen, I have a missfire in my 348gts. I have gone through a vast number of checks to pin point the cause, and I'll spare you the details for the moment. What I would like to do before I go further is pull any fault codes from the ECUs. I have the procedure, but not the test switch to connect to the 3 wire test cable at the ECUs. Does anyone know how the switch is configured?
Cheers, Mike.

 

Jimmie, I did a search and came up empty. Must have used the wrong key words, so thanks for this link, It's exactly what I was looking for. Cheers, Mike.

 

Thanks all for the advice. I had already done the basics. Changed the ignition pick ups, they were rotten, new spark plugs, one had a broken insulator, checked the HT leads, all around 13k ohms, cleaned every earthing point I could find, treated every connector with the stabilant stuff. None of this made a difference. So I will try to pull the codes this weekend before I start spending on coils and such. When I checked the coils, I measured around 1 ohm on the primary side (centre pin to the two outside pins), which feels about right. But I got 40 plus meg ohm between the coil posts to ground and this seems wrong.
Is there a test for them.
Thanks, Mike.