Stand alone harness question

[Jason 56]

I’m installing a 2016 L83/8L90 in my 56’. I have everything figured out with the harness except which wire to hook to the ignition switch. All the diagrams show the switch going to the BCM then a dashed line (no wire identification) to the ECM. Just wondering if anyone has any experience that can help.

[gmc684x4]

The dashed lines are for you to supply and hook up there should be a tail of the aftermarket harness to supply power to that is marked for each circuit

[nsb29]

This looks like a wiring harness that was reworked A picture of your diagram would help

[Jason 56]

Sorry I didn’t clarify in my original post but, I’m doing my own stand alone harness. The starter relay signal comes from the ecu so I assume the ignition switch signal must go to the ecu first. Just need to know which wire in the ecu receives the signal

[rodstored-72]

I am not sure if this is right or helps.. but I am doing a '13 swap into my '86. I believe that the wire just needs to be "tied\plugged" into the truck fuse box where a slot is just for "key on\start" check on LT1swap & see if there is a pinout diagram (find on web) that is for '16. Also look for the fuse panel diagram (on this site) on the truck to tell you where the slot\wire is for this source.

hope this might help... good luck!!

[Jason 56]

Here’s some diagrams. The first two are of the factory fuse panel for engine controls which I duplicated. Except the downstream O2 sensors. The 3rd picture is the ignition schematic. Looks like the violet/yellow wire is the one I’m looking for but, it‘a called the accessory data wakeup (Pin 70)? Not sure if that’s the one? The 4th image is the starter schematic. That one has a violet/lt green wire coming from the main ignition relay. It’s labeled run/crank ignition 1 voltage (pin 51). Not sure which wire I should use. The labels are from the last picture which is the blue X1 pin out for the ECM. Pin 63 runs to the starter relay to activate it. Nothing in all the ECM pin outs is labeled ignition signal!