Put a voltmeter across the battery terminals.

What is the DC V at rest?
What is the DC V when holding the key in the crank position?

Also, You checked continuity of wires, but did you check for the operation of the relays as described?

Junkyard ECM? No problem with that, except you don't know what brought that donor car to the junkyard.....

Can you find 12V at the IP BATT fuse terminal (one or the other vs ground?
That would at least confirm SOME current is making its way from the battery to the trunk. You said some things in the car work.......electrically,
yet have ANY V at the starter -- either the 12V from the battery ot the purple wire from the fuse box when cranking?

 

12 volts at starter main cable no power at purple wire at starter when trying to crank . Will crank but not start if I close the relay 31 manually . No ground to pin 86

 

Well you got it to crank! Now I have to go back and look at the schematic to see what your symptoms mean...

 

So it seems relay 31 is malfunctioning/ not functioning.
Multiple possibilities.
1). The coil inside the relay is broken. Open circuit.
2). The wire between relay 31 pin 86 and the ECM pin for the starter coil control (yellow wire) is damaged/open, thereby not grounding pin 86 on relay 31. Again, open circuit.

Are you manually closing relay 31 by jumping pins 30 and 87 or by manually grounding pin 86 on relay 31?. The latter will tell you if the relay coil is intact since the circuit doesn't care where the ground is from, just that it appears when cranking to complete the circuit and close relay 31. Try this alternate ground of 86 but only when cranking. The former tells you the starter and the purple wiring are intact. Now the cranking issue seems narrowed down to the really 31 or the wiring from the ECM to pin 86.

 

I took the cover off relay 31 and closing by hand

 

What's the resistance across relay 31 85 and 86 while not cranking?

What's the voltage drop fr pin 85 to engine ground while not cranking and while cranking?

 

 

My resoning: Trying to see if relay coil is the issue 85 & 86, or if control signal to it is the problem.

Just trying to save some dinero.

 

I know this post is old, and sorry to hijack it, but the jumper of the pins got my car to turn over continuously (while jumped), but I couldn't get it started.

Background:
2007 Saturn Ion 3 2.2L Sedan
360,000 miles

Had someone replace my A/C. Within a week, got stranded due to a blown Ignition fuse (10A). Kept blowing them occasionally. Sometimes before crank, sometimes after. Twice, while shifting from Drive to Park, it shut off on me. Luckily, I was already at my destination.

Back in August 2023, it stopped cranking altogether. Parked in driveway on incline. Couldn't get it into garage to lift it up until last week.

Starter is good (bench test by me, bench test at O'Reilly). Fuses are all currently good. Relays are all currently good (even have a new one to interchange).

I've had trouble in the past with the ignition holding onto the key, but not every time, and I'd override with the button. I've tried cranking in Park and Neutral.

I'd appreciate any suggestions as I see the help available here is thoughtful and genuine.
If I need to start my own thread about this, then let me know and I will.

 

You should start a new thread.