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Good stuff Mike. Tried to rep you but gotta spread the love first

 

Alvaro, the communications network is a "twisted pair" set of wires. It is connected to the DLC under the dash, and the wire colors are given in the "description of operation" text I posted.

The troubleshooting matrix is long, and is broken down into each concern or failure that you can experience with the system. I posted all of "J" in the matrix, which deals with the twisted pair network being down and not working. It walks you through step-by-step on how to find the problem. Start at J1, and work your way to J13 until you figure it out.

The reason I asked about the door chime...It is part of the system that tells the computer that the key is in the ignition. If the computer can't "see" the key is in the ignition, then it won't act like it is.

 

Here is pinpoint test K:

 

And here are some more test methods from the PCM diagnosis book:

 

That was my problem when my port stopped communicating. Fuses get old too.

 

 

 

Here are the manuals I use:


These cover everything but the engine. That is in the next book.


This is the most valuable tool any 7.3L owner can have. Period.