Over the last week I have had two incorrect fuel gauge readings. Both times were when I was low on gas (less than a quarter tank or 330+ miles). What occurred was that when I started the car, the fuel needle shot up as if I had a full tank of gas. Then, it slowly goes back to its correct position, or a little below it. This occurred today for the second time in a week. Both times the car was parked on a flat surface (my driveway). I'm thinking it would be the fuel sending unit starting to go bad, as that is what reads how much gas is left in the tank. It shouldn't be the entire fuel pump as that would actually SEND the fuel and the car would cut out while running. Anyone have this symptom with their GS at all? If so, what was the solution?

 

I had the same problem a few months back, where the readings were that I had 1/4 tank, but when I went to fill it up, I could only put $20 worth in. So in most cases, I had a full tank, but the reading was off. I took the car in, and they said it was either the fuel sending unit, or the sub sending unit. The funny thing is that right after the day i took it in, the problem stopped and it hasnt happened ever since.

Another member on the boards had it happen to his GS, and then it also corrected itself shortly there after. I dont know how common this is, but if it happens again on my car, I will have both the sending units replaced.

 

I was actually stranded on the Highway on Friday due to incorrect readings. My fuel gauge showed I had 1/2 a tank but then all of a sudden my car stopped acelerating and I ran out of gas. I had to call my dealer and he came with some Gas and the gauge was off a bit until yesterday when it returned to normal. I think if you let the gas go way beyond "E" the gases and the deposits may affect the gauge reading. I learned that you must fill up before that little Empty light comes on.

 

Hrm... I always fill up right after the light goes on It's an addicting habit that one day i'll regret.. But I definitely did not know that the car could stop working because of a gauge malfunction

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1999 Lexus GS400
-Stock

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Regardless of when the light comes on, I know that if it reaches 400 miles or city driving... Im going to be out of gas REALLY soon. I reset Trip A at every fill up, so I know what to expect from each tank.

 

EXACTLY,
I drove from San Francisco to Santa Ana California yesterday on one tank. I filled up at exactly 400 miles. My light was on, and when I did fill up, it only took 17.2 gallons. We have 19.8 gallons to use. I also reset at least one of my trip computers at each fill-up and calculate the gallons. I got 23 miles per gallon on premium.

The fuel gage has a mind of its' own. On the road, I normally get about 100 miles on 1/4, 200 on the half, 300 around 3/4, and then it holds its' own for a long time before going to E just before 400 miles. If I drive in the city, the mileage is much worse. I have seen 110 miles on 1/2 tank, so hot rodding does take its' toll on your fuel, and your wallet.

 

I had the same problem, took it to the dealer and found out the fuel sending sensor was bad, so they replaced the main sending sensor and the sub sensor ( yes there are 2 sensors for the fuel guage). if that doesnt fix it. there is a sensor / relay in the dash board that has to be changed
****be vey careful pulling the dash I've heard horror storys of guys shorting out there dashboard trying to work on them the electronics are very very fragile......by the way all the sensor were under warranty I dont know how much they cost...

 

hey guys, do you know how much the snesors would cost to replace?
my car has 57k and out of warranty.

 

Do you know what the sensor is called?

 

Do you know what the relay is called?