You have moved/changed so many that I dont know where you can start..

Run a health scan (if you have a decent scanner), tell us what comes up..

 

The bad thing is you disconnected the battery, so any history/pending/freeze frame data which would assist in diagnostic has been erased..

 

The only OBDII code displayed before I reset the ECU was P0350. Before I replaced the spark plugs and wires there was no P0350 error but there were some that indicated random misfires on cylinders 1, 3 & 5.

I really haven't changed that much. Just the spark plugs and ignition wires. After the replacement a single wire to one of the coil packs didn't get connected well and I ran the engine with a coil pack disconnected.

What is a 'health check'?

 

Update... I have procured a clever little oscilloscope and have been able to determine that the coil packs are each receiving a trigger pulse train from the ECU but I still get no spark.
I check for spark by removing a spark plug, putting it back in its boot, grounding the threads against the block and watching for a spark in the gap while someone cranks the engine for me.

The pulses peak at 6VDC and I wonder if that is correct.

This was obtained by removing the sockets from the coil pack plug, stabbing them back onto the coil pack's pins and clipping a lead to the trigger terminal.
The signal looked the same when measured at the ECU (ie no voltage drop).

 

Are you saying that you see control, but no spark ?
Have you confirmed you have 12vdc and ground at the coil, ?
12vdc, control, ground if you have the 3wire COPs

 

Correct. Control pulses, but no spark. I verified 12V power, but the ground is doing something odd. As you can see in the photo, I have hooked one lead of my multimeter to the ground lead of cylinder 2's COP (and have verified that it is not touching the other 2 leads) and the other lead to the battery's negative post. The other two COPs have been disconnected. With everything off, it reads 3Ω. When I turn the key to Run it reads ~350Ω. As I crank the engine it reads 6MΩ. After I attempt to start the engine, but with the key still in the Run position, it reads ~1MΩ. When I turn the key off it drops to 70Ω until the mail relay clicks off, at which point it returns to 3Ω again.

I recognize that those crazy high resistances are likely the cause of the lack of spark. Now I need to figure out what is causing the crazy high resistance.

The ECM is now reporting a P1631. That error can be associated with CAN bus communication issues so maybe the crazy ground is messing with the CAN bus too.

While the key is in the Run position, the tach, which is usually inoperative, starts bouncing around like crazy... not in a discernable pattern but in a crazy random way.

 

I would like you to confirm the 12vdc, use an incandescent test light.

Circuits (unloaded) may show voltage, but incapable of supporting power (amps).

Next confirm the ground with the light, from battery (+) to COP ground (-), do not perform these tests without the load (light).

I suspect you have a bad connection on one of these circuits.

 

Ok. I'll try the light tomorrow.

I looked at the schematic and noticed that the ground lines from the COPs go through a connector and then go directly to ground on the plate that holds the ECU under the passenger side floorboard. I checked the resistance between the COP ground and the ECU plate and it was 2Ω. Cool.

I attached the positive lead of my meter to the big grounding line bolt on the back of the intake manifold and the negative lead to the negative post of the battery. It was also 2Ω. Cool.

Here's the kicker tho: when I turned the key to the Run position, the resistance shot up to ~200Ω. When I cranked the engine the resistance went to ~8MΩ. When I stopped cranking the resistance dropped to ~600MΩ and when I turned the key to Off the reading dropped back to 2Ω after the main and fan relays opened. The resistance between engine ground and the negative battery post would change depending on the position of the key. Shouldn't the resistance between the engine and the negative battery post always be something like 2Ω? I mean, if there is 8MΩ resistance between the engine ground and the battery ground wouldn't that functionally be an open circuit? What could cause such behavior?

 

That is because you have a bad ground connection, it shows up under load, you cannot rely on the resistance reported by the meter...

 

Issue solved. It was the ignition failure sensor (IFS).

I noticed that the 12V supply to the COPs is entirely supplied through the IFS. As you indicated, when under load while cranking, the voltage coming out of the IFS to the COPs dropped to 7V. When I disconnected it and fed the COPs directly from the battery, I got spark. So I unplugged the IFS and bypassed it by connecting together sockets 1 (power to IFS) & 2 (power out to COPS) of the harness so that the COPs would get their 12V directly from the power supply line for the IFS.

The Sorento now starts and runs and my bypass will work until the new IFS gets here in a couple of weeks.

 

Hurrah, good for you, well done !