The fuel gauge in my 1998 LS400 seems to be inaccurate. Its reading almost 3/4 tank but in the message center it says my range is 58 miles. Which should I trust? The only way I can think of is to fill it up and subtract the gallons I put in from the capacity. Does that make any sense?

 

That's all you can do for now til you figure out what's wrong. You don't want to run it out and cause problems with the fuel pump.

 

My gage is off also in my 98... but I find the range value is dead on. A little bit of testing will show your range meter may be more accurate and the one to follow. I usually fill up after about 300 miles.

 

I filled the tank this morning with the needle gauge showing exactly 1/2 tank and the range as 53 miles. It took 19.2 gallons to fill it so I guess I will trust the range message instead of the gauge. I don't guess there is a "reset" option that I could try. Anyone know?

Thanks,
hms09

 

Attached is the way to check the amount of gas and the voltage at the sender gauge connector. There are 3 pins. Pin #1 is grounded, Pin #3 is supplied 5.0V from the cluster unit, Pin #2 is the read out voltage from a variable resistor connected to the float. When the float moves from the lowest to the highest, the read out voltage should swing almost 0V to nearly 5V thoroughly without any glitch. You'd better check these.

Regarding the reset, there is no special method. All you can do is just disconnect the battery and after waiting several minutes simply connect it.
Hope this helps.