Posting in 4th Gen forum as my car is a 2007 Limited V6 (with about 130K miles), but I imagine some of the discussion will be relevant to other generations.

Also, I've read through some of the other posts here on fuel gauge issues and sending unit replacement and watched several videos, e.g. Tim the Toolman...I have a few specific questions, though, and wasn't sure if I should kick up any more dust on the other long threads. So starting this one.

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A week or so ago I filled my gas tank. The next day (or two?) when I went to start my car in the a.m. I noticed that the fuel gauge needle on instrument panel remained pegged at empty with the amber "low fuel" warning light on. I knew it wasn't a low gas situation, although I went to nearest gas station to top off anyway just to be sure (tank was still almost full). Also, the "range" (aka miles-to-go) digital read-out still indicated I had ~375 miles to go before empty.

I drove around the rest of the day and needle remained set on "empty". But next day when I started car, fuel gauge was reading full and has been working normally/as expected since (e.g. it now reads 2/5 full).

So, some questions:

1) Given the "one-time-only" occurrence, how concerned should I be right now? Do I wait until it is permanently mis-reports fuel level or address it now?

2) How can the needle be reading empty but the "range" readout not be affected (as in still be accurate)? I would have assumed both had to tie back into what the system thought fuel level was?

3) I understand that for my car I can access a fuel tank hatch under back seats although for some dumb reason I can't replace anything from this access hatch...is it worth pulling the seats to inspect and or clean off something and/or test something. Or, again, should I wait until issue is permanent or at least actually occurring in real time.

4) A general automotive expert I know suggested that if the low fuel warning light is on but needle is stuck on empty, that the fact that the light is on may indicate source of issue is likely the instrument cluster. Does this make sense?

My best guess is that the fuel level sensor in the tank is OK and sending the proper signal, which goes to the instrument cluster and I would also think the signal is also send separately to the ECU responsible for the mileage calculations, I'm not 100% sure that's how it works but I do know that each of the gauges is the instrument cluster has a "stepper motor" to make each gauge work, so I think what is happening is the fuel gauge stepper motor is going bad, but the ECU is still getting the signal to the center info readout for mileage calculations.

These stepper motors can be replaced without replacing the entire instrument cluster, but it involves de-soldering the old/defective one and then soldering in the new stepper motor.

But wait for other replies, hopefully someone may know more on this....maybe @BlackWorksInc will stop by and comment, he's a Toyota Tech and could possibly give a more precise answer.

That all being said I myself would wait until it becomes a permanent issue before fixing it, it may never happen again and you can always stop and get gas if you're worried about getting too low if it does happen again, but in the meantime I would do exactly what you're doing now and getting as much info that could be causing the issue and sourcing parts for the future if needed.

I am going to say it's possibly a sticking/finicky fuel sender unit, it wouldn't be the first to have oddball dropouts, but since it's only happened once I can't quite say for sure and testing it properly will require removal of the fuel pump assembly (which at that point I'd just install a new one for peace of mind if I am going to drop the fuel tank and pull it out for how relatively cheap it is).

It is possible that the combination meter is having an issue, but I would say it's probably not likely given that the combination meter also turned on the "E" light; which means it thinks it low rather than say a stepper motor is failing intermittently. I'm thinking either the sender is sticking/has some stuff on the printed rheostat or there's some sort of intermittent connection in the circuit between the sender and the combination meter (unlikely, but possible).

As for the lie-o-meter/Multi-Information display not updating correctly? Well... that thing has been a sort of unsolved mystery on the forum for years. But I did find some scraps of information I missed long ago when I was trying to theorize how it works in other threads. It doesn't fully shed light on how it works, but it gives me a better idea and brings some context to some oddities I have noticed over the years. I'll have to dig in deeper and I think I'll need to make a thread once I have time to make sense of all this disparate bits of data...

Anyways, the really cut down version is that the fuel gauge sender only has minimal input on the MPG and Range Modes. It seems like the vehicle only looks for a fuel level signal every once in a while and only when it changes drastically (like filling up/topping off a decent amount), that lets it know to "reset" the Range calculation; otherwise much of the actual miles remaining is based on calculations derived from the MPG calculation and some other factors. It's possible since your fuel sender was acting up in the "Empty" position, the vehicle didn't see it as a refueling event and never updated the Range calculation to reflect it had been emptied and refilled. It's also possible had you driven it long enough in that state it might have corrected itself, but not sure.

As for accessing the fuel pump through the 2nd row seat access cover; you cannot unfortunately. It's there to allow you access to the electrical connectors and fuel lines going into the pump assembly so you can disconnect them before dropping the tank. It's honestly one of the stupidest designs that was implemented on a few vehicles Toyota has made... They really should have just made the panel big enough to pull the fuel pump assembly out with it. You have to drop the fuel tank to access the fuel pump assembly properly (unless you want to cut the hole bigger in your body like some people have... not something I personally recommend).

But it's up to you if you want to fix this or not. If it's only the first time it's happened, maybe wait for it to become more consistent?

Thanks for the info and insights, everyone. I'll sit tight until it's an "actual" issue rather than a curiosity-inducing one-off. If it does become a real issue, then, in the words of The Terminator, "I'll be back"