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"

aa040371, did the problem ever return? If so, did you fix it? I just experienced this for the first time too. Restarted the vehicle, and it was fine again.

Hello. The problem still persists and in fact has become more pronounced, in that reliably now the gauge drops to "Empty" about half a tank in, i.e. after I fill up it reads fine, and then reads fairly accurately down to about half a tank at which point it drops to "E" every time and stays there until I fill up again.

As pointed out above, it is almost certainly the sending unit located inside of fuel tank, which Toyota geniuses decided to make easy to see (from inside the car via hatch accessed from under 2nd seat row), but rather difficult to actually change out, requiring dropping the fuel tank. So I've just left as is and fill up when my trip odometer reads about 350 miles or so (car has ~380-mile range when full).

I have the same problem with amother auto unless you want to replace the sending unit and i don't, just keep a running track of your driven miles and don't let the tank get to empty.

Yep...that's what I mentioned in just previous post that I already do. It comes with risk, of course...coincidently, with regard to this discussion, I just ran my vehicle out of gas because I was paying attention to the mileage/miles driven, but had driven a few days since last fill-up with a trailer hooked up, and I didn't think to consider the effect of that extra weight/drag on MPG. Doh!!

Had similar fuel instrument cluster issue. It turns out the cluster gauge was bad. Happy it was not the sending unit.

For my issue I always just assumed it was the sending unit, based on observable behavior. Is there a straightforward way to determine if the gauge in instrument cluster is the culprit?

I installed a replacement cluster which worked perfectly. That eliminated sending unit. I did not know in advance if the sending unit or cluster was bad so no, I do not have a straightforward way.

You may not want to go the hack job route, but I'm glad I did. Multi tool and a carbide blade to enlarge the opening, some tin sheet, and some 5mil rubber to make my own little hatch with about 4 self tapping screws and 1 of the existing ones.
Tin Sheets Rubber Sheets

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@4RunnerAquasport : you are saying this opening you cut lets you get at, even replace, the sending unit? Also, which one of the three cars you have listed was this for, please?

I'm pretty sure it's his 4th Gen, under the diver's rear seat there's a access hole for disconnecting the wires/fuel lines to the fuel pump/gas tank prior to dropping the fuel tank, but it's not big enough to remove the fuel pump, so many will enlarge the hole so they don't have to drop the fuel tank to replace the fuel pump, the sending unit is a part of the fuel pump.

If I ever have to replace my fuel pump I will be enlarging that hole!!!

Yes @AuSeeker is correct, it's my 4th gen. I believe the 5th gen can be done this way also, but I cannot confirm that.