I think I finally found the right schematics for my lnf swap to wire in the bcm so I can get around the security features.
But I don't know how to figure out the reference points on the paper verses real life.
here is the schematic
Red arrow points to bcm. The bcm has many connections on it not in a straight line. How do I know what number on the paper goes to which spot on the bcm?
Here is the bcm
I have about 4 sensor/things to wire up to the bcm and all I have now is a jumble of wires.
Any one have any advice?
There's usually also a connector diagram that maps positions to numbers. I think some of the GM connectors also have the numbers molded into them, but you may need the eyesight of a teenager to see them.
If the unit is in a dashed outline, that means not all terminals used are listed in that image.
The connectors are labeled with an underlined X(number). I see X1, X2, X3, and X4. From there you get the terminal numbers. Some are labeled in column/row format like X4, which is usually only done for the big screw-in bulkhead connectors like that pink sucker. The others are labeled with pin numbers, which are sometimes actually on the connector housing.
You will ideally find the connector view diagram, which has the terminal locations labeled. GM also tells you a general idea of what the wire is, along with the circuit number. Like to pick one at random, connector X2 pin 20 is serial data low, tan wire, circuit 2501.
Mostly just adding to what Keith posted. I honestly did not know that about the dashed vs solid outline until two days ago so I wish to share 
i wish everyone was as nice as GM for wiring diagrams. I like track diagrams too, but not when they only list stuff like r35/28 and you have to go to three separate charts to figure anything out.
In reply to Pete. (l33t FS) :
I didn't know about the dashed vs solid lines until just now :)
Thank you. I will have to look a little closer to see if the connectors are labeled. But what you guys said has helped me understand it.
Oh, the connectors won't be labeled for X-whatever. You need a component view for that, or infer it from the diagrams.
GM is at least nice in that the connector view also lists the part numbers for the connector shells and terminals. Getting that information can be impossible for some makes.
A lot of this is fresh in my mind thanks to a 2010 CTS last week that needed some deep down wiring diag. Trying to find the computer end of the engine wires I needed was "fun" because the connector views listed all three engines available and the shell layout only corresponded to the CTS-V, which was the polar opposite car. Turns out it had a 2011 computer and harness even though it was mid 2010 production and the emissions sticker proudly stayed it was a MY2010 vehicle.
GM likes to hang on to wiring colors and circuit numbers for-ev-er but change the actual hardware on a whim.
When I did my first engine swap I imported a JDM MR2 half-cut. Wiring diagrams are even more fun when you have to translate from kanji/hiragana to english and then figure out how to merge the two. But that project taught me a love for reading wiring diagrams. The GM one above is pretty nice - it at least gives you a general location of where the grounds are located. The Js on there are junctions/splices in the wire run, so are good places to look first if you have any broken circuits.
There should be a component table / diagram that shows the locations of the connectors. Most multi-pin connectors will have a 1 pin and last pin marked for orientation, so a 20-pin connector will have a 1 and 20 molded into the plug. Most multi-pin connectors will have multiple circuits that aren't all depicted on a single drawing. Once you find one, find a known wire color so that you can orient yourself on the connector - so you can tell which side of the plug it's numbered from. It's pretty easy on components, but juntion-junction connectors could be numbered on the male or female side of the connector.
Here's a Toyota one for comparison. Most of the concepts carry over between mfgs.
You should have a legend that shows the location of all the connectors in the diagram, like this:
Personal experience says wiring problems are usually within a couple inches of a connector if not the connector itself . Plus bulkhead connectors are an easy place to divide and conquer.
