2017 Tundra Immobilised, literally!

Good Day Everyone! Not sure if anyone can help? I have a 2017 Tundra 5.7 SR 5 that does 1 of 4 things when I try and start it.
1. It just cranks but doesn't fire
2. It fires for 2/3 seconds then shuts off
3. It fires for 0.5 second then shuts off
4. It fires up first time and runs like nothing has ever happened and off I drive into the distance....until I turn it off and try and restart it.
My start up procedure would always be a mixture of the above, obviously ending in stage 4.

I tried disconnecting the battery for 24hrs, that seemed to do something, I had a week of normal driving, then the gremlins returned.
I'm on a tiny island in the Caribbean, no Toyota dealer to run it to, the best help I've had is a garage ran a fault check with a computer when it wouldn't start. Code P1604 and B2799.
I know it has something to do with the immobiliser, I have 2 chipped keys with fobs and a bare key. I have the same issue whichever key I use, security light on the dash goes out when key is inserted. It was so intermittent, the last 3/4 days it just started getting harder to start to the point now where Ive been sat at home for 2 days and can't get that damn thing to go.
Ive seen guys resetting ECU's using a paperclip, that's how desperate I am.
So if money was not necessarily an issue where would you guys start with replacing parts? Because I'm losing money everyday I'm sat at home.
Thanks in advance guys!

 

Is it the stock battery? Did the shop load test they battery? Bad batteries do weird things to these trucks and if it’s stock from 2017 then it’s most likely done. I’d test the battery before throwing money at something else.

 

Hi Tim, I did actually replace the battery recently thinking it might be an issue.
Initially I thought it was the fuel pump going but checked and have good pressure during cranking.
After every start attempt I would take the key out and wait a while then reinsert the key, maybe I was just imagining it but doing that gave me a better chance of it starting.

 

Id still load test the battery, I have purchased brand new batteries and had them have bad cells or other issues.

is your truck flex fuel? I am thinking it is?

p1604 is a starting fault, if you have flex fuel truck could be related to the alcohol density. Search and you will get hits.

Other code is often related to a bad chip in the key or some other issue with the immobilizer system.

But, Tundras will give faults and alerts, seemingly unrelated issues, if a battery had low power or a bad cell as the trucks systems are not getting the full power they need.

and look around under the hood and cab for any rodent damage wires.

 

There has been a lot of stories about rodents chewing wires ... partial chews causing intermittent issues, etc. Just something easy to check.

Battery check suggestion is a good one. I had issues with bunch of dash lights due to weak battery.

 

Yes Frank its a FFV

 

I had a good look underneath this morning, rats did cross my mind and we have them around. Everything looks in good shape, conduit is pretty heavy duty on the body and Ive checked what I can see under the hood. I'll take the battery and get it tested. Just got to figure out how to get there!

 

There have been issues with the flex fuel and startability. Most recent fix is fuel pump and I think a software update. There is T-SB-0166-19 on it.

But I would check wires for rodent damage, battery first.