Low fuel light works but doesnt
#1
04-03-2019, 10:51 AM
Low fuel light works but doesnt
I'm posting here because I believe its electrical. I'm a little confused on my findings, and cant find a specific answer to my question so far.
2000 jimmy slt 4door 4x4
"Low fuel" light lights up upon starting engine, but when the tank is empty or low, it does not come on. I'm thinking it might be the pressure sensor on the fuel pump.
Could someone point me in the right direction if this is not correct?
2000 jimmy slt 4door 4x4
"Low fuel" light lights up upon starting engine, but when the tank is empty or low, it does not come on. I'm thinking it might be the pressure sensor on the fuel pump.
Could someone point me in the right direction if this is not correct?
#2
04-03-2019, 11:04 AM
The pressure sensor that is in the fuel pump assembly is used for EVAP monitoring and has nothing to do with the fuel level gauge in the dash.
Have you literally run it out of fuel and not had the light come on? It should come on with around 4-5 gallons remaining.
Quite frankly, you should never be getting that low in the first place as the pumps in these trucks like to be fully immersed in fuel to keep them cool. The fuel that is returning from the engine into the reservoir around the pump helps, but not enough it seems. They are quite well known for blowing pumps even if the tank is kept above 1/4, but the pump life drops quite a bit when continuously run low on fuel.
*EDIT* - Here is the low fuel light turn on/off criteria from the 'Scantool Data Definitions - Outputs' for the instrument panel:
And here is the information regarding the fuel level sender data and what happens to it.
You could take a peek at the monitored & displayed fuel level with a compatible scan tool to see if there is something weird going on with the filtering of the fuel level, but if your gauge works properly otherwise, you shouldn't have a problem there.
Have you literally run it out of fuel and not had the light come on? It should come on with around 4-5 gallons remaining.
Quite frankly, you should never be getting that low in the first place as the pumps in these trucks like to be fully immersed in fuel to keep them cool. The fuel that is returning from the engine into the reservoir around the pump helps, but not enough it seems. They are quite well known for blowing pumps even if the tank is kept above 1/4, but the pump life drops quite a bit when continuously run low on fuel.
*EDIT* - Here is the low fuel light turn on/off criteria from the 'Scantool Data Definitions - Outputs' for the instrument panel:
LOW FUEL LAMP
Range: ON/OFF
This output refers to the commanded state of the LOW FUEL indicator. ON is displayed when the instrument cluster is commanding the LOW FUEL indicator ON. OFF is displayed when the instrument cluster is not commanding the LOW FUEL indicator ON. The instrument cluster will command the LOW FUEL indicator ON under the following conditions:
Range: ON/OFF
This output refers to the commanded state of the LOW FUEL indicator. ON is displayed when the instrument cluster is commanding the LOW FUEL indicator ON. OFF is displayed when the instrument cluster is not commanding the LOW FUEL indicator ON. The instrument cluster will command the LOW FUEL indicator ON under the following conditions:
- When the instrument cluster receives a class 2 (percent monitored fuel level) message of less than 19.2 percent from the VCM/PCM. Once the indicator is ON, the Monitored Fuel Level must rise above 23 percent in order to turn the indicator OFF.
- During the bulb check period. The bulb check will begin once the ignition switch is first turned to RUN position, and will last for 3 seconds .
- A class 2 communication failure has occurred between the instrument cluster and the VCM/PCM.
And here is the information regarding the fuel level sender data and what happens to it.
MONITORED FUEL LEVEL
Range: 0-100 percent
The fuel gauge sender monitors the level of fuel in the tank and sends this information to the VCM/PCM. The VCM/PCM then sends this information to the instrument cluster over the class 2 serial data line. If a class 2 communication failure occurs, this data will be 40% .
DISPLAYED FUEL LEVEL
Range: 0-100 percent
The VCM/PCM receives the displayed fuel level information from the fuel gauge sender. The VCM/PCM then sends the displayed fuel level information to the instrument cluster over the class 2 serial data line. The instrument cluster then processes this information and displays it using the fuel gauge. The displayed fuel level information refers to the information the instrument cluster is processing and attempting to display on the fuel gauge. This data may be different from the monitored fuel level for a period of time due to filtering. If a class 2 communication failure occurs, this data will be 0%.
Range: 0-100 percent
The fuel gauge sender monitors the level of fuel in the tank and sends this information to the VCM/PCM. The VCM/PCM then sends this information to the instrument cluster over the class 2 serial data line. If a class 2 communication failure occurs, this data will be 40% .
DISPLAYED FUEL LEVEL
Range: 0-100 percent
The VCM/PCM receives the displayed fuel level information from the fuel gauge sender. The VCM/PCM then sends the displayed fuel level information to the instrument cluster over the class 2 serial data line. The instrument cluster then processes this information and displays it using the fuel gauge. The displayed fuel level information refers to the information the instrument cluster is processing and attempting to display on the fuel gauge. This data may be different from the monitored fuel level for a period of time due to filtering. If a class 2 communication failure occurs, this data will be 0%.
You could take a peek at the monitored & displayed fuel level with a compatible scan tool to see if there is something weird going on with the filtering of the fuel level, but if your gauge works properly otherwise, you shouldn't have a problem there.
#3
04-03-2019, 12:00 PM
Thanks for that. I thought that was an evap sensor but wasnt sure. The gauge works fine, and only reason why I got my mom to run it so low, is because I wanted to check the over gas mileage. She said the light never same on and as soon as i out some in with a Jerry can, truck runs great.
Will be looking into your reply and see what i can get when she gets off of work.
Thanks!
Will be looking into your reply and see what i can get when she gets off of work.
Thanks!
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