On most cars, fuel pump either work fine OR just die. They DON'T give any sign that it is dying. It happen to me 4x on all my company's cars/trucks (not Toyota). The cars/trucks just die when the fuel pump goes bad (and won't restart), the only thing that my drivers notice was the fuel pump was getting lauder.
But so far, my Toyota's fuel pump has never die on me yet.
FASTMR2 is correct, typically you get no warning it just crapps out.
However sometimes you do get a warning. If after driving for ~30 min or so the car just dies for no reason and will not restart...and a few minutes later it will restart fine and it seems the problem went away.
That could be the fuel pump going. Fuel pumps that are on the way out get hot and fail...sometimes they will work for a short time longer if is has a chance to cool down.
On my 88 LeSabre, I got an extra 2 weeks of use before it died and would not come back to life... i.e. tow time.
In my mk3 turbo supra I had a bad pump. It didn't go out though, I had high egts and ran like crap for so long. Everyone told me it wasn't my pump. So I want to Homedepot and bought a $6 water pressure gauge and bought a T. I "T"ed it into my fuel line and saw that I was only getting 25 psi at 10 psi of boost. I couldn't beleive my motor was still alive with 17:1 A/Fs. I ran the car like that for 6 months of A/F's at 17:1 at 10 psi. Needless to say the car ran great when I put the new pump in. A new pump never hurts on a car that has over 150k on it.
When the fuel pump was going bad on the 93T the engine would buckle above 4k rpms and AFR's shoot lean for a bit. Likewise I have had fuel pumps "slowly die" on other cars. When it did eventually crap out the pump could not push 20psi fuel pressure and the engine refused to idle longer than ten seconds.