Low fuel indicator light on Honda

The low fuel indicator light has quit working on my 1999 Honda Civic. My wife ran out of gas one night and I want to fix it. The fuel gauge itself still works.

I removed the instrument cluster and found that the bulb does work.

I got to the top of the gas tank by swinging the back seat bottom cushion out of the way. I unplugged the three electrical connectors there and inspected the wiring. It all looked OK and I plugged things back together.

It will take some driving to get to a low-fuel condition and see if the light is somehow working now. If i does not, what next? Replace the fuel gauge sending unit in the gas tank? (It seems the switch that turns on the low-fuel indicator light is incorporated in that unit - is that right?)

If I remember correctly the low fuel light is operated by part of the fuel level sending unit which is in the gas tank. If you’ve verified that the bulb and wiring are good then you will need to replace the sending unit in the tank. You state that the fuel gauge itself still works properly, but you also say that your wife ran out of gas. If you added gas and the car started I don’t see how the gauge can be working properly, it should have read empty when she ran out.

Did you use a VOM to verify continuity of the wiring?

Well just looking at my Acura manual that should be similar, looks like either the sending unit in the tank or the guage module. I suspect it is quite expensive and requires calibration when replacing. There is a self diagnostic mode but is too complicated even with a manual, and also a sending unit test that requires the Honda test equipment. So probably going to have to spend a couple hundred just for the diagnosis from the dealer. The one thing though is to check all of the fuses. There are a couple that could cause a problem.

I couldn’t tell you if any of my low fuel lights work or not because they have never gone on. I fill up when I get below a half tank. Back in the old nuclear war days of bomb shelters, it was drilled into out heads to make sure we had enough gas to get out of town at all times. Major power outages and storms do happen which can make getting gas in an emergency a bit of a problem. I know its like talking to the wall, so what I do is just check the wife’s car from time to time and go fill it up for her. If its not the fuses, I think you are looking at a fairly large repair bill for what I consider a novelty item.

You will probably need a new sending unit as the low fuel light is usually controlled by a thermistor on the unit.
A thermistor is a resistor that changes resistance based on temperature.

The gasoline keeps it cooled down while immersed and the circuit open. When the thermistor is exposed to air after the fuel level drops low enough the resistance changes and closes the electrical circuit from the bulb when then causes the bulb to illuminate.

I have not pulled a schematic up and determined what color of wire from the bulb is involved but grounding that wire as a test should cause the bulb to turn on. Hope that helps.

The schematic does indicate a thermistor. Thank you for explaining what it is and how it works. I didn’t test continuity of the wiring (good idea, jt, but I didn’t think of that.) Looks like a new sending unit is needed.

How common is this problem? I wonder if 10% ethanol in the gasoline is a factor in it.

This may be a stupid question but, if the gauge works why do you even need the light? Doesn’t the needle being really close to the big letter E just scream “find thyself a fuel station”. I understand the light is a convenience but IMHO not the only thing telling you to get fuel.

Sounds kinda like my wife.
One would think…think ,that the E should mean something but in the daily rat-race just running around town she doesn’t even look at the speedometer ( keeping up or in with traffic ) let alone the other gauges.
Every now and then she’ll just up and tell ME…’‘go see if I need gas.’’

The light can serve as a backup indicator separate from the gauge. Some cars get down to under 1/8 of a tank on the gauge and may run out of gas in 5 miles. Others may go 150 on the same gauge reading.

My Lincoln even has a third option; it beeps on the Message Center and provides a readout of how many miles are left on the remaining few gallons.

On both vehicles , I leave the messege center on ‘‘miles to empty’’ at all times unless I want to know something else.
But do you think she’d look there too ?
’'my car beeped at me…go see what it wants. ‘’

I would fill the tank sooner then later its a lot easer on the fuel pump

I guess its a cultural thing. We might as well get used to it. I’m sitting at the computer and I know exactly where the gas gauge needles are on all three cars. The one is a little over 1/2 but I’ll be filling that up when I go to the store. I also know how much is in the lawn mower tank and how much is left in the 5 gallon can for the mower. I dunno. No point whipping a dead horse I guess.

The only thing more annoying than a message center beep are those 80s era Nissans with the voice boxes.

Trying to repair something on the car with a monotone robotic female voice repeating the same phrase over and over can be very frustrating.
About the 99th time that box says, “The door is open… the door is__open…the door is open…” or “The fuel level__ is low…The fuel level__ is low…” the urge to throw something becomes pretty strong. :slight_smile: