no power to under dash fuse panel

I'm having a similar problem with my 2016 Tundra. Tuesday afternoon everything working fine. Next morning truck started fine but no power to windows, speedometer, turn signals, shifter interlock, radio, a/c, wipers, etc. I haven't done any recent work on the truck and there's no evidence of rodents. I checked the under dash fuse box, the inboard strip of fuses has 12v but no power on the outboard side even with ignition on. I checked the 7.5A AM1 fuse, it has 12v but no improvement swapping the fuse with another. Looked at the other fuses, nothing seems bad.

Any suggestions? Appreciate any help.

 

Are you sure you are checking the correct fuse, the 7.5A AM1 fuse has been misidentified before. Study the diagram on the fuse box cover to make sure you are on the right one.

If the AM1 fuse is good, almost every fuse in the interior fuse box should have 12V with key on.

Can you verify which fuses dont have power with the key on?

 

Thanks for the diagram. Yes, confident I checked the AM1 fuse, it's easy to find next to the larger 30A fuse next to another 7.5A fuse. It looked fine, had continuity. I replaced it with a new one. Still the same.

That side of the panel has power with key to acc/on. The other side has no power.

 

Seems the relays are not closing as the key comes on. If you have 12V+ power on both side of the AM1 fuse the only other thing to keep the relays from closing would be a bad ground wire.

Count the fuses in the row to make absolutely certain you are on the AM1 fuse, verify it has 12V on both sides. If it does you could check the ground wire or check the relay power wire into the body control module. Wonder if you have a wiring break around the ignition switch in the steering column

 

This should help its for the 2016 specifically

I would look for 12V on Pink wire pin 45 connector DD with key on and then Light Green wire pin 43 connector DD with key on. The AM1 fuse could be good and be sending 12V out to the ignition switch but its not coming back in to close the relays. Like I said might have a broken wire around the ignition switch.

 

***RESOLVED*** 2016 Tundra Platinum, no power to half the fuse box

You called it, broken wire near the ignition switch.

I opened the lower dash to get the fuse panel box accessible. While I was thinking about how to best test those pins I decided to remove the plastic shrouds around the steering column. Quickly saw the broken white wire. This wire is coming from the ignition switch (it had 12v on ignition side) and must be involved in the relay circuits. Seems it broke at the T-tap from the red wire. These wires move a lot when the steering wheel moves out of the way when the truck is turned off/on. My guess is the T-tap made a fulcrum on the white wire and after years of bending it finally broke. It seems a less than ideal place for a T-tap but this is how it came from the factory. I made a soldered connection for the white and red wires and everything works.

Your direction on where to look and providing wiring diagrams is much appreciated! Saved lots of time and money. Thank you!

 

Great news.

Yes the 12v power goes through the 7.5A AM1 fuse out of the interior fuse box into the ignition switch. When the ignition switch closes it sends this same 12v power signal back into the interior fuse box to the relays. When the relay coils are charged they close and power the rest of the fuse box.

You had the power signal coming out of the interior fuse box but never making it through the ignition switch and back to the relays.

 

The whole look of it makes me think there was an error at the factory. To put T-splices on wires in a moving part seems like an afterthought or fix of an error.

Another thing that makes me wonder is the broken white wire had 12v power on the ignition side, the fuse box side of it did not. Indicating power made it to the ignition but not back to fuse box. From the wiring diagrams I was expecting it to be a light green, gray, pink, or possibly an orange wire taking the 12v to the fuse box relays. I didn't take the time to trace the white wire to the pin on the DD connector.