Good man, glad it’s resolved.

I started this thread kinda in the middle of my story.

I went in under the intake to do some pre-emptive maintenance to the secondary air pump crap. Why it's under the intake is not a question I have answers for, other than dumb design.

The air pump has a small mower-like sponge filter in it, which has been a nightmare for Tundra's with 2UZ-FE. The more that pump runs (cold engines in colder climates) the more that little filter gets sucked into the blower motor (fused with 50A) and clogs up the valves that feed that air into exhaust, which is supposed to help heat the cats faster. When the related DTC's are logged the owner has to pay near $3000 to have a dealer fix it. OEM parts are about $800. I removed the little sponge filter and attached a K&N-like clamp-on air filter to the inlet snout of the fan assembly (a common thing to do).

So, my little filter was still there, but signs/evidence the fan blades were starting to suck it in. I also inspected the motor itself, and no sheet, they wrapped one lead wire around the body and over the other wire before exiting the assembly. No sheeting, the two wires were chaffing each other and the pos had visible copper. So I had to fix that about-to-happen problem.

In prep for doing that work I got some 'new' injectors and new plugs. Figured then was the time to do it.

All that work went ok, then the no-start issue. I did some initial testing in the relay box and the C/OPN relay did not work as "I" expected it to, but in fact it was working as designed. I then came looking for some answers as to why what I was seeing did not make sense...... hence my initial post. Along the way I did learn for safety reasons the C/OPN relay will not engage w/o a signal from crank sensor, or if an airbag is deployed. This is ECU functionality/info that is not well known by many. I had even talked to my dealer service manager guy, who told me the fuel pump turns on as soon as the key gets to run/on position, which is just bs. The ECM will only start the pump during starting cycle, and stick it on when ECM detects a running engine.

So, that's the long story of it.

Miller time ;)

It is always the jobs that eat your lunch, where you end up learning a lot . Nice work sorting it ajl out, and good job on welding up the hole under the seat .
On to the next adventure ,

I will add that your service manager is correct. All late model vehicles energize the fuel pump briefly before actual crank. Some by unlocking with key fob, or when the fob is near / in the 'slit' with your foot on the brake pedal. This ensures correct line pressure at initial crank.

Maybe I read it completely wrong, but all 4-6 fuel injectors were stuck? Or is it TBI?
An engine would at least run poorly with one or two not working.

His setup is PFI, which has been the standard but quickly giving way to direct injection. One thing I would like add is with newer vehicles the drivers in the ECM that control the ignition coils and fuel injectors ( and circuits) are much more 'sensitive' to load / resistance. So say you pull the wire connector to the coil pack or injector with the engine running the driver will shut down until restart or some until you clear memory and restart.

So no injector code was thrown.
Plus the entire engine shut down because of one single mechanically-stuck injector?
Those boys over in Yokohama sure won't be designing Russian tanks anytime soon!

https://scanneranswers.com/p0201-obd2-trouble-code-generic-dtc-fault/
P0200 OBD-II Trouble Code: Injector Circuit Malfunction
P0201 OBD2 Trouble Code ✔️- Time to replace an Injector
P0203 OBD2 Trouble Code - check your fuel injector and wiring!
P0292 OBD-II Trouble Code: Cylinder 11 Injector Circuit High

Not on the GX470. The ECM will not engage C/OPN relay unless two conditions are true, 1) key asks for a start, and 2) during start cranking there's a signal from the crank sensor. Both must be there for the ECM to engage the relay and to start-up the EFI side (injectors and spark). Once it starts running the ECM switches from start-mode to run-mode.

This unknown snafu of #1 and #2 is the reason why the C/OPN relay appears to be not working if you just turn key from off to run/on.

The ECM has no way of knowing if the mechanical side of an injector is good or bad in start-mode (see note below). It can only monitor injector coil current. No/low current is a high-ohms issue, short/hi current is a low ohms issue.

And no............, it would not start, because 6 of the 8 were stuck closed. See vid in post #19.

Note: I purposely left the last injector alone after bumping 7 of them. Wanted to see if it would start. It did start, but ECM threw some dash lights and DTC. Turns out while in run-mode the ECM detected cyl #6 was in mis-fire. In fact it was no fire because that injector was still stuck closed. Engine was running but only on 7 fires. I went back and bumped #6 to unstick it.

So, the ECM can detect something related to mis-fire (which could be no fuel, or bad spark, etc), but only does that when engine is running. Many of the ECM monitors are engine running monitors, and some of them are the 2-trip type.

It's not ez to diagnose some things when the engine is stuck in a small area ("state", in this case a no-start state) and the ECM does not have much self-diagnostics in that state.

I didn't know exactly what relay that was before, but it brings back a memory.
https://www.rav4world.com/threads/fuse-box-is-missing-c-opn-fuse.189337/
"C/OPN is the fuel pump control circuit relay"

Apples vs. old oranges....but similarly I once had an '89 VW Golf which tended to randomly die, sometimes in traffic, at an intersection while rush hour waited, on the way to work.

The car also had an unfixed coolant problem which added to the problem solving.
It popped the bypass climate radiator spraying fluid inside the car and in my face on a 100deg day on the bridge.
Had to bypass the interior climate heat radiator with plumbing elbows and a hose from a hardware store a mile away.
Keeping it from overheating was an ongoing thing. Three different thermostats and a radiator didn't fix it.
Sitting in stuck California traffic with the hood cracked, fan on high, and all windows down was hell.

Once it was running it usually stayed running.

Hot restart was usually a problem especially on hot days for some reason, which led me down the wrong path.
I was looking at the twice-changed fuel filter, and then fuel pump, and then lines for vapor lock, and then into replacing coil and crank sensor.

It finally turned out to be the burned up Bosche relay which still worked 90% of the time.