Low Fuel Light not working

omniphil · **Posted:** Sat Apr 30, 2016 5:48 am

The gas gauge works fine, I was down to maybe a 16th of a tank and it took 18.7 gallons. Seems about right, however the low fuel light never came on. (No chime or anything either)

Has anyone else had this happen? I figured the low fuel light would be tied to the fuel level sensor and that appears to be working fine.

papaindigo · **Posted:** Sat Apr 30, 2016 3:30 pm

Would help if your signature said what model year and gasser vs CRD but I'll assume gasser since this is on the KJ general forum. The 05/06 tank holds 20.6 US (not Imperial) gallons (based on conversion of 78 liters to gallons but in reality it will likely hold a good bit more depending on the setting of the pump's automatic cutoff and/or whether you typically try to top off the tank after the automatic cutoff kicks in. Based on past experience with DCJ vehicles you can likely get 1-1.5 more fuel into the tank than the nominal 20.6 gallon capacity.

In theory the low fuel light comes on with 2.3 gallons left in the tank but as a practical matter, in my experience, the exact time it triggers, again based on past DCJ experience, could be anywhere from 2.0 or less to 2.5 or more.

Given 18.7 fill, assuming pump gauge is right, and a hypothetical 2.3 reserve with the low fuel light off you have a full tank figure of 21 gallons well within the range of error, per the above, that would not trigger the low fuel light.

Best bet:
1. turn the ignition key to on but not run - does the low fuel light come on (looks like a pump on left lower side of ignition cluster (N. American market)?
2. invoke an instrument cluster test by by holding the trip odometer button while turning the ignition on. It will cycle through all bulbs and gauges which I think includes the low fuel light. Does it come on?

If yes to 1 and/or 2 the light is fine you just did not run the tank low enough try again OR the ECU/PCM, not sure which, is not telling light to come on based on sending unit level (sending unit wiring is ok as gauge works). FYI I've gone so far as to lug a gas can along and run to empty on a gasser to check how much fuel really remains. Do NOT try this with a diesel, in fact unless you know where diesel stations are don't ever run until the light comes on, just fill up when tank gets to 1/4 except in I-10 in West TX in which case do it more like at 1/2.

If no light to either the bulb is gone. Can be replaced with LED (dealer will want to install new cluster) but may not be worth your effort, email me for how to if interested.

omniphil · **Posted:** Sun May 01, 2016 6:47 am

papaindigo wrote:

Would help if your signature said what model year and gasser vs CRD but I'll assume gasser since this is on the KJ general forum. The 05/06 tank holds 20.6 US (not Imperial) gallons (based on conversion of 78 liters to gallons but in reality it will likely hold a good bit more depending on the setting of the pump's automatic cutoff and/or whether you typically try to top off the tank after the automatic cutoff kicks in. Based on past experience with DCJ vehicles you can likely get 1-1.5 more fuel into the tank than the nominal 20.6 gallon capacity.

In theory the low fuel light comes on with 2.3 gallons left in the tank but as a practical matter, in my experience, the exact time it triggers, again based on past DCJ experience, could be anywhere from 2.0 or less to 2.5 or more.

Given 18.7 fill, assuming pump gauge is right, and a hypothetical 2.3 reserve with the low fuel light off you have a full tank figure of 21 gallons well within the range of error, per the above, that would not trigger the low fuel light.

Best bet:
1. turn the ignition key to on but not run - does the low fuel light come on (looks like a pump on left lower side of ignition cluster (N. American market)?
2. invoke an instrument cluster test by by holding the trip odometer button while turning the ignition on. It will cycle through all bulbs and gauges which I think includes the low fuel light. Does it come on?

If yes to 1 and/or 2 the light is fine you just did not run the tank low enough try again OR the ECU/PCM, not sure which, is not telling light to come on based on sending unit level (sending unit wiring is ok as gauge works). FYI I've gone so far as to lug a gas can along and run to empty on a gasser to check how much fuel really remains. Do NOT try this with a diesel, in fact unless you know where diesel stations are don't ever run until the light comes on, just fill up when tank gets to 1/4 except in I-10 in West TX in which case do it more like at 1/2.

If no light to either the bulb is gone. Can be replaced with LED (dealer will want to install new cluster) but may not be worth your effort, email me for how to if interested.

I updated my signature

Yes, 3.7 liter

Thanks for the things to try, I had no idea there was a bulb test, that's pretty neat.
I have run it down to the needle being right on empty, an still no low fuel light or chime. So I will do your testing and report back.

Thanks!

omniphil · **Posted:** Thu May 05, 2016 2:13 pm

Fuel light certainly works. Doing that test mode on startup shows it light up...

I doubt its me not running the tank low enough, it will get to the E and still no light...

papaindigo · **Posted:** Sun May 08, 2016 12:43 pm

You know the low fuel light bulb is ok and you know the fuel gauge needle works so... When you invoked the cluster check did the fuel gauge needle cycle E, 1/4, 1/2, 3/4, F? If no then the gauge needs to be calibrated which can only be done with a dealer or equivalent scan tool. If yes then either no signal is being sent to turn on the bulb or you just have not run the tank low enough. Keep in mind "E" on a fuel gauge is a somewhat arbitrary mark when it comes to how much fuel is actually left in the tank. Here is what you can try:
1. drive until the gauge gets down to near empty put a gallon or so gas can full of gas, preferably a spill proof can, in a small utility trailer if you have a hitch or in a buddy's pickup bed for a drive along.
2. immediately go out for a drive and either a) you will run out of fuel without the light coming on in which case use the gas in the can to get to a gas station or b) the light will come on.

If a) then you can dig into why but that may require a dealer or you can just live without the light as we all did for decades before that option was added to vehicles. Digging back in the dim recesses of my memory dealers, at least in the past, can tell the ECU "when" (as in how much fuel is left based on the scan tool estimate) to turn on the low fuel light.

If b) now you know the low fuel light actually works but you don't know how much fuel is actually left. The only way to know that is to drive until you run out of fuel and refill. I've not tried this but in theory if you can safely carry say 5 gallons of fuel, see 1 above, plus an empty container(s) into which you can pour measured amounts of fuel then drive until you run out. Pour in 1 measured gallon crank the KJ back up and immediately shut down. Put the ignition in the on but not run position so your helper can see the fuel gauge and the low fuel light. Continue adding measured amounts of fuel until the low fuel light goes off. Add those amounts up for what's left when the low fuel light comes on.

omniphil · **Posted:** Mon May 09, 2016 9:12 am

papaindigo wrote:

You know the low fuel light bulb is ok and you know the fuel gauge needle works so... When you invoked the cluster check did the fuel gauge needle cycle E, 1/4, 1/2, 3/4, F? If no then the gauge needs to be calibrated which can only be done with a dealer or equivalent scan tool. If yes then either no signal is being sent to turn on the bulb or you just have not run the tank low enough. Keep in mind "E" on a fuel gauge is a somewhat arbitrary mark when it comes to how much fuel is actually left in the tank. Here is what you can try:
1. drive until the gauge gets down to near empty put a gallon or so gas can full of gas, preferably a spill proof can, in a small utility trailer if you have a hitch or in a buddy's pickup bed for a drive along.
2. immediately go out for a drive and either a) you will run out of fuel without the light coming on in which case use the gas in the can to get to a gas station or b) the light will come on.

If a) then you can dig into why but that may require a dealer or you can just live without the light as we all did for decades before that option was added to vehicles. Digging back in the dim recesses of my memory dealers, at least in the past, can tell the ECU "when" (as in how much fuel is left based on the scan tool estimate) to turn on the low fuel light.

If b) now you know the low fuel light actually works but you don't know how much fuel is actually left. The only way to know that is to drive until you run out of fuel and refill. I've not tried this but in theory if you can safely carry say 5 gallons of fuel, see 1 above, plus an empty container(s) into which you can pour measured amounts of fuel then drive until you run out. Pour in 1 measured gallon crank the KJ back up and immediately shut down. Put the ignition in the on but not run position so your helper can see the fuel gauge and the low fuel light. Continue adding measured amounts of fuel until the low fuel light goes off. Add those amounts up for what's left when the low fuel light comes on.

Super informative and detailed post. I appreciate the help!
I will go test that the needles sweeps on cluster check...

I think at this point I'll just live without the light, it's not a big deal, was more just curious why it wasn't functioning..

papaindigo · **Posted:** Mon May 09, 2016 10:45 am

I honestly have no clue when that light comes on in my KJ CRD as running out without an in tank fuel pump on a diesel can potentially be a real problem as you have to manually reprime the fuel lines. It's less of a hassle on the KJ CRD than on my old Dodge Cummins whose owner's manual effectively says if you run out you can add diesel to the tank and frantically pump this tiny little lever but it's probably a good idea to call the tow truck while you pump. Much safe to fill up before the light comes on.

That said I once had a Plymouth minivan whose light came on at a scant 1 gallon left and was able to get the dealer to reprogram the light to come on with more like 2.5 gallons left. You might consider that the next time you are in for Dealer service as it shouldn't take more than 15min labor time to hook the gauge up and reprogram the light to come on "sooner" (e.g. while there is more fuel left in the tank)

USPLibby · **Joined:** Thu Jul 28, 2005 12:29 am **Posts:** 372

As long as the other gauges are working, I wouldn't worry about it too much.

If you start to see various gauges and lights stop working at random times = replacement cluster time. The dealer wanted around $1000 for a new replacement cluster installed. I found a used 2004 cluster on Ebay for $60 and everything works great, except for the extra light that comes on. My Jeep never had the tire pressure senors, but for $940 bucks less, I can live with it.

HoosierJeeper · **Joined:** Sun Feb 15, 2009 8:23 am **Posts:** 1218

Mine does not come on till the range is in the single digits. I see mine maybe once a year. The needle has to be all the way on e.

Sir Sam · **Posted:** Fri Aug 12, 2016 9:42 am

papaindigo wrote:

I honestly have no clue when that light comes on in my KJ CRD as running out without an in tank fuel pump on a diesel can potentially be a real problem as you have to manually reprime the fuel lines. It's less of a hassle on the KJ CRD than on my old Dodge Cummins whose owner's manual effectively says if you run out you can add diesel to the tank and frantically pump this tiny little lever but it's probably a good idea to call the tow truck while you pump. Much safe to fill up before the light comes on.

That said I once had a Plymouth minivan whose light came on at a scant 1 gallon left and was able to get the dealer to reprogram the light to come on with more like 2.5 gallons left. You might consider that the next time you are in for Dealer service as it shouldn't take more than 15min labor time to hook the gauge up and reprogram the light to come on "sooner" (e.g. while there is more fuel left in the tank)

I do not believe this is possible to update the setpoint for the light to come on in the KJ. I've been all through the setup options and have not seen it.

That said, I could be wrong.

Low Fuel Light not working

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