P0453 HELP! Obscure Repair NOT canister assembly or ECU

I have a 2006 Tundra 4.7 SR5. I'm an ASE certified technician and have been in the field for years. Fuel and emissions diagnostic is something I excel in. This is the first time in 10 years I am ever asking a question on forum because I am genuinely stumped.
Problem: P0453 Evap Emissions System Pressure Sensor/Switch High. The code is permanent. No amount of clearing or reset will erase CEL. Multiple diagnoses and repairs don't work.
1. There isn't a pressure switch on the 2006, heck I'd test a known good if they sold one.
2. Pressure on this one is run through the Vapor Vent Valve attached to the Fuel Vapor Storage Canister Assembly.
3. Smoke Test showed leak at vent valve and bad gas cap. Changed out entire Storage Canister with Vent Valve assembly (aftermarket) with toyota gas cap. Passed smoke test after repairs. No leaks. Code still on. Will not clear.
4. Replaced with genuine toyota part. Code still on will not clear.
5. Tested voltage at connector located under driver seat. 5v. Pass.
6. Tested fuel pressure at rail, perfect.
7. Per Toyota's testing procedures, last step is ECU. Before replacing ECU I had independently diagnosed by both a local repair facility and by Toyota themselves. Paid for both diagnostics (even though I had already diagnosed myself) and both independently came up with replacing the ECU as the only solution. Replaced with ECU and relearn successful but code/fault was on as soon as vehicle started. Still will not clear. Toyota has no clue, suggested this forum. Identifix has nothing. Every master I know over the past 10 years has no clue. I am at a loss and can't sell this truck until I fix it.

At this point I have replaced everything that can be replaced. Please help. Has anyone encountered tis issue.

 

@shifty` and @empty_lord

 

Have you tested voltage and resistance at the plug at the charcoal canister? Couldn't figure out how to load the file but here's a long screen shot of the repair procedure directly from tis. Probably will have to click on it a zoom.

 

I'm no help to anybody here in this thread. But heres your screenshot all blown up, and zoomed in.

 

Definitely did not translate very well. Sorry.

 

What’s with tundras and weird electoral issues this week? I’ve got one. Stumping me at work.

Short of checking literally pin on the ecm related to the evap system, I wouldn’t be surprised if it’s ecu. I have had 2 trucks (not this vintage, but similar) with burn marks on the board that ended up being tied to the evap pump. It’s not hard to pop the ecm out and take the screws out to check the board. Might be the quick check before delving into diagrams

 

@pgstewart316 Where is the pressure switch located. I know you say that you can't get a switch independently, but can you pull the the whole "module" that the switch is in, if there is one... from a junkyard truck?

You were clear in your post, but I'm tired. Let me clarify something here, you replaced the storage canister with vent valve assembly with aftermarket first, and then replaced that same part with Toyota OEM later?

 

@Lextech @Tundra2 Yes, have tested resistance at plug at canister as well as voltage. Voltage is about 4.9-5.0 volts. Resistance is less than 100 ohms. about 92. The procedure you screenshot has been performed by me, a tech at an indy shop and a tech at toyota. All three of us came to same conclusion regarding ECU. @Tundra2 to clarify, yes the storage canister with vent valve assembly has been replaced with toyota OEM.

This fault is permanent, can't be cleared, permanently stored. Once new ECU was installed yesterday the code was immediately on as soon as the truck was turned back on. Toyota basically told me good luck. At this point there is literally nothing left to throw at it.

 

Have you tried your ECU in a different truck to see if the code will clear?

Could be a wiring issue in the harness you're not picking up with the voltage/resistance test (ie: it doesn't happen until running/driving).

 

Is it possible that the sensor is correct and the pressure really is high?

Is there a way you can "plug into" the system with a manual gauge to determine actual pressure?