No crank no start U0100 Code?

Excuse my artwork, but here you can see there is a Turn signal bulb being powered by an ECM B+, with a multimeter on the Positive side of the circuit. If you were getting a reading of 2volts for example, that means you would be losing that 2volts in between the two meter leads, thats a voltage drop test. You can do the same test on the ground side and see if there is any voltage drop there as well.
Its not as complicated as it sounds. The meter is just comparing the reading from one lead to the other, or the difference in voltage potential. You want zero voltage drop, but with a load and current flow you will have some per connection in the circuit.
Just start by checking for power,

Please let us know what the final fault actually is. It helps others that may run into the same issue. Thank you

Ok thanks I will

Appreciate it.

I have circuit test tester

What kind of circuit tester? Does it load the circuit with at least a few amps? A turn signal bulb is what I use mostly because they have a high inrush of current, then still pull 3 or 4 amps. A circuit tester or short finder, whatever the case may be might not reveal a circuit with corrosion, because if it just tests for circuit continuity, thats not a loaded test. Its just a resistance test. A wire with every single strain copper broken except one will still show zero resistance, whereas with a loaded test, if the bulb doesnt light, the circuit cant carry current.

Ok witch wire do u want me to test now

I have posted the ECM connector pinouts already. Go back on page 2, there are the ECM powers and ground in the X1 and X2 connectors.

I have cheap power probe tester

I would use a regular test light when checking powers and grounds, you need to be able to load test the powers and ground.

I have a make a load tester

ok are you still unsure about the testing? If you want to check how much current flow your setup pulls, your multimeter should be able to take a quick reading with the meter set to the 10Amp setting, most meters say Fused, (under 15 seconds on most multimeters or it will blow the fuse inside), and moving the Red meter lead to the other 10Amp port and put the meter in-series with the light bulb, doesnt matter if youre on the positive or negative side, you will get an amperage reading real quick, write it down so you know how much that specific bulb pulls for current. Before you know it you'll have a set of all different size testing bulbs to pull varying amounts of current.
This is very helpful if you want to learn more about the electrical side of an automotive system. Just remember to take a quick reading, then let the meter sit for something like 10 minutes before testing current again.

As for the testing a power feed wire, you're going to back probe the wire on the back of the ECM connector, turn the key On, and I just have my setup ready, so I can quickly connect up and disconnect the test bulb.
We dont want to pull constant higher amperage on these power feeds, we just need to know that wire can carry enough current. The bulb should light up brightly for at least a few seconds.
This way you are only pulling current from that wire's fuse to the ECM connector and not pulling high amps threw the ECM. This test is not testing the ECM but just the wiring to it.
Same test with the Ground wire on the X2 connector, except you will be hooking the test light to battery positive and using the ground coming from the X2 connector.
Here are the ECM connector pinouts again with notes. But dont proceed if you are unsure or not confident with electrical testing, you have to be extra careful when testing right at the ECM connectors. Heres a couple guides to help.

https://2carpros.com/articles/how-to-use-a-test-light-circuit-tester/
https://2carpros.com/articles/how-to-check-wiring/

Ok I made a headlight bulb test light

Using 9005 h3b bulb test light 73 ground lit very bright
..

Testing ignition pink wire bulb lit very bright

Pin 73 on x2 and 20 on x1

Nice work AL514 :)

Ok what's the next step?

What have you done so far?

Using 9005 h3b bulb test light 73 ground lit very bright
..

Testing ignition pink wire bulb lit very bright

Pin 73 on x2 and 20 on x1 both show bright light when testing

I would go back over this post again, we must have missed something.

What do u mean ?

I mean you have diagrams and guides, please recheck your work to make sure we did not miss anything