Will not stay running

Joe thanks a lot of the reply and information! I have checked all of the fuses and relays. All the fuses are good and all of the relays work mechanically. Now what I don't know if if the relays are allowing the proper voltage through and not getting cut down by bad contacts inside the relays. My car has a push button ignition and an immobilizer key. I don't think it's an immobilizer issue because I'm able to lock and unlock the doors and the instrument panel shows the key as being recognized. Now I will say this. This did have an aftermarket remote start to it that I removed that bypassed the immobilizer. I removed it by tracing the wires from the component back to where they were connected to the harness and clipped them and taped them at that point. Now with regards to the crank sensor. Let me take a step back. Sometimes I do see the tachometer moving, esp when the car battery is fully charged, but then there are sometimes it doesn't move. I'm not sure if the speed of the rotation of the crank has anything to do with it registering on the tach or not. The sensor has two wires coming from it, both with about 2.3 or 2.4 volts at both female connection points (I always thought one was supposed to be ground) so combined that is a little less than the 5 volt reference it is supposed to be. The crank sensor is new and I've had it out and had the multimeter connected to it, moves a piece of metal back and forth across it and it did produce A/C, so it is working, but the insert is just a little shorter than the original OEM prong. So I guess it might not be picking up the magnetism like it should be. Today I pulled a couple of plugs to check for spark. Put the plug in the coil, attached one negative side of jumper cables to engine and the other to the shank of the plug. Had my son turn the car over and if it didn't fire then no spark was produced, but when it did briefly fire it did produce a spark (obviously since it fired) but the times it didn't produce a spark I had my son continue to crank it and no spark was produced. There were a couple times he cranked the motor for 10 seconds and it never produced a spark, but, like I'd mentioned, the times I saw the spark the other cylinders (or at least some of them) fired. I also tested for injector activation by putting a piece of paper over the plug hole and had my son crank the engine again for several seconds. The one time I did this there was not any fuel mist on the paper. As I'm sure you know the ECU sends signals to those components to spray and fire.
Ultimately it appears the fuel and the spark are random, so, at least in my opinion, the crank sensor isn't sending consistent info to the ECU so the ECU can send consistent info to the fuel pump and injectors, or the ECU is faulty in sending and receiving information. Of course the ignition sends the signal to the ECU to fire IF the brake pedal sensor sends info to the ECU to let it know it's okay to start the car. Just so, so many things it could be. But the only code is a P0560. So the OBD2 is of no help. Just very odd that this all started with the car stalling and starting and stalling and starting enough to et it him, but once home and cooled down overnight the only thing now is a crank, no start.A crank, a brief fire, and then a cut off, or a couple of times only a crank, start, and rev for about 5 to 10 seconds before it cutting off again. Not sure if the heat of the engine caused something to expand and increase contact, and then it contract when cold and reducing contact. Thus the behavior when this whole ordeal started as compared to the next morning after it cooled.
Sorry this was such length and thanks for the help. Also, I forgot if I mentioned this was a 3.8 automatic direct injection engine with drive by wire throttle control.

So sorry. Yes, there is an approximately 5 volt combined reference on the coil connections with the ignition on. One connection point in the harness is 3.4 and the other around 1.65. I should have included that information beforehand. Also, for both cam sensors, with the ignition on, there is a 4.7 volt reference on the signal wire, a 4.9 volt reference on the positive wire, and verified ground on the ground wire. I have tried to back probe the crank sensor but it is nearly impossible because of the gauge of the two connected wires and the location of the sensor. Also, not sure if it makes any difference, but this car is a 2015 3.8 with a 2013 3.8 engine in it. The motors are the exact same but I noticed the wiring harness part number for the 2013 car is different than the part number for the 2014 and 2015 car. (Just found this out yesterday) Never have been able to figure out what the difference was. In any event the harness that came with the car is the one that is being used and since the engines are the same and everything "fits" then I'm figuring this isn't an issue as the car was driving fine before this issue started. Thanks again for the help.

Another thing to add just a fyi. Compression is around 145 give or take 5 in each cylinder, and I understand it's suppose to be about 169, but the compression was done dry and on a cold engine too. Just can't do a compression test on a warm engine because I can't get it to run and warm up. :) I suppose the more accurate picture would be the PSI after a wet test was done. The engine does have around 75,000 on it so a little wear is expected I suppose.

Thank you again. I did verify ground to Pins #48, #49, #50 on the injector distribution box connection, and also verified voltage on pins #30, #44, #59. All three between 2.4v and 2.6 v.

That being said, going back to the crank position sensor. Is that suppose to show up on the tach every time the car is cranked? Seems like yesterday when I was verifying the compression there were times where I was cranking the engine to build the pressure, but most of the time the tach wasn't moving. Every now and then it would bump a little bit, but by no means was it consistent. Seems to show up when the battery is at top charge but stops showing up as the battery weakens. Thanks again for the help. Tremendous information you're sharing.

I do not have access to live data but I did use some alligator clips and a multimeter to verify the crank was putting out a pulsating voltage when the engine was being cranked. I will include the video of the readout. Although the pins on the injector control box checked out properly per your information I'm not sure if the signal is getting to the injectors. I'm also questioning the fuel pressure regulator within the fuel pump unit. If i'm not mIstaken the FPR regulates the fuel pressure based on the pressure in the intake manifold so as to create the proper fuel/air mixture? Also, I do need to include that I rarely hear the fuel pump prime when the ignition is turned on. And I can definitely hear it as I can hear it running from the outside of the car when I have jumped the fuel pressure relay. I may hear it prime one time out of every twenty or thirty crank/start/shuts off cycles. Then again this pump might be the type that doesn't prime but only pumps fuel when the motor is actually cranking. Thanks

Unfortunately it's a GDI engine and I don't have access to the injectors or the connections, but today I was able to get it to start and it actually ran for about 30 seconds idled on its own for prob 10 seconds before shutting off again. But after that happened I decided to check the fuel pressure on the low pressure hose so I disconnected it at the high pressure fuel pump and there was pressure, and then I wanted to check the high pressure so I unscrewed the high pressure connection at the rail and there was pressure there too, but since then I can't get the car to fire anymore. I checked two of the plugs for arc and neither are arcing, lol. I did invest in a Blue Driver OBD diagnostic tool and it did show a code I hadn't previously seen and I'm not sure how long it has been there, but it was a P0685 code. Also I removed the EMS relay and was unable to find any ground on that fuse panel connection. If i'm not mistaken one of the five connect points is suppose to be a direct ground. As I'm sure you know the Blue Driver allows me to access a decent amount of live data. Thanks again

Greetings,

I checked the ECM harness per the information above and this is what I came up with, and these readings on the positive points are with the ignition in the "on" position
#'s 5, 6, 30, 55, 80 (Grounds) all measured 5.2 Ohms

#52 Battery 12.26 volts
#75 ECR Relay "on" input .87 volts
#77 Battery 12.26 volts
#94 ECR control 12.25 volts
#99 ECR "on" input .87 volts
#100 ECR "on" input.87 volts
. So it appears the ECR main relay is only transferring.87 to the to the ECR "on" inputs when energized.

I am a bit confused on testing the ECR per instructions as on the diagram page that shows measurements A and B it mentions if "no" then replace with a known good fuel pump relay, so I tested both of the relays per the instructions. Unfortunately the fuel pump relay doesn't have a schematic diagram on it like the ECR does
For the ECR the control pins (85 & 86) are showing 16.2 ohms and the load pins (87a and 30) are showing infinity. With the ignition off there is a constant voltage at both pins 86 and 30.
The FPR the control pins ( the darker bronze pins on the picture) are showing 88 ohms and the load pins (the two lighter gold colored pins) are showing infinity. The only pin on the FPR that has a constant voltage with the ignition off is the bronze pin furthest right. Also, and finally I was unable to locate a ground on the ECR connection at the fuse box with the ignition on or off. My apologies again for the length and thank you

Goodness, it ended up being a loose female terminal connection for one of the switch pins for the ECM. I put a new ECM in and checked the power and grounds for the ECU and they were showing the same as they were with the old ECM with several showing.86 volts, so I decided to get a read at the terminal itself so I shaved a wired and jammed it into the terminal with the switch pin of the ECM and it went from.86 volts to 12.4 volts and heard the fuel pump priming too when I opened the door. Car started right up and idled good. Drove it around for a bit and it did fine! Still curious why I could never find a ground at the ECM, but I'm not going to complain. I'm sort of scared to remove the wire though, lol. Thank you so much for your help and all of the information. Would have never been able to find the issue without it Thank you!

You do the same. You've got a great site! Five stars.
Thanks again