You should have checked the resistance across the test light. If it’s extremely low you can’t just short signal (purple) to low reference like you did, which is why it likely still ready empty before you cleared the code. For earlier GM trucks the range is 40 ohms for empty and 250 ohms for full. You probably introduced a momentary amount of resistance within that range (just moving wires around can do that) and the gauge on the instrument cluster will move slower than what the PCM reads. Next time use a variable resistor (like a 1 k potentiometer) between signal and ground and you will confirm signal integrity better. Also your scan tool should be able to display fuel level so you don’t need a partner to validate the level.
Ebraheem Azhar Thanks for your input!! I love using a test light! it's easier to use and I know the scan tool has a PID for fuel level but I wanted to make sure the gauge on the cluster was working!! I enjoyed your comment thanks for commenting and sharing your knowledge...
I have same van but my code is p0464 and my guage is reading fine not empty, but check engine light is on and that code is on, so my problem is the same sensor fuel level?
Thank you! I have an odd one... My 06 express 3500 just started acting up. When I turn the van on sometimes, the gas light is on... Then after a few minutes, it registeres an actual level. Is that my sending unit starting to go bad?
Alan Gaudry very good question, the test light acts as a buffer in this case, ( kinda like a resistor ) to reduce current flow... shorting the reference wire to ground might damage the ECM or just throw a code, but its better to be on the safe side by using a test light
mohammadabid 1222 yes you most likely have the same problem... follow the steps on the video and you will be able to find your problem, you have to have a scan tool to erase the trouble codes before you start doing the tests.... Good luck!!!!
08 chevy 3500 hd cab and chasis 4x4 6.0 with dual tanks, I can trigger my gauge sweep, fuel sending unit has resistance that should indicate 15% fuel in front tank. my gauge reads empty, I am trying to find the origin of the signal to the gauge? what are the possibilities' thanks Rich
I have the p0463 code on a jeep commander. However, my guage works sometimes but other times it stays on F or E. I also notice that when the check engine light is on and the guage is not correct, my reverse (backup) lights also do not work. But when the check engine light is off and my guage is right the back lights work. Does this still sound like a faulty sending unit? I had the fuel pump and sending unit changed about 13 months ago.
Ken Simek that sounds like a shared ground problem... you have to look at a wiring diagram to see where all these circuits connect, if you can't get wiring diagrams you should have someone look at it for you...
i have a same problem but it started when i was change the computer harness..my fuel pump is everything working and good but still empty indicator guage. how can i find in alots of wiring in the computer harness cause too much wiring.
searched the internet and couldn't figure this out. After watching you it was a bad ground thank you very much !
Glen Hoerschgen My Pleasure!!
Hey where was that ground located? Thanks
Thank you. Good job explaining the how and why.
Great JOB..... I like how you explain everything 👍👍👍
Jose Arevalo Thank you!!
You really make great videos. Thanks!
Timothy Horne My Pleasure!!
You should have checked the resistance across the test light. If it’s extremely low you can’t just short signal (purple) to low reference like you did, which is why it likely still ready empty before you cleared the code. For earlier GM trucks the range is 40 ohms for empty and 250 ohms for full. You probably introduced a momentary amount of resistance within that range (just moving wires around can do that) and the gauge on the instrument cluster will move slower than what the PCM reads. Next time use a variable resistor (like a 1 k potentiometer) between signal and ground and you will confirm signal integrity better. Also your scan tool should be able to display fuel level so you don’t need a partner to validate the level.
Ebraheem Azhar Thanks for your input!! I love using a test light! it's easier to use and I know the scan tool has a PID for fuel level but I wanted to make sure the gauge on the cluster was working!! I enjoyed your comment thanks for commenting and sharing your knowledge...
I have same van but my code is p0464 and my guage is reading fine not empty, but check engine light is on and that code is on, so my problem is the same sensor fuel level?
@sdfv4zx yes it could be, you should have it diagnosed!!
Thank you! I have an odd one... My 06 express 3500 just started acting up. When I turn the van on sometimes, the gas light is on... Then after a few minutes, it registeres an actual level. Is that my sending unit starting to go bad?
DWES ENTERPRISE you probably have a wiring issue or the sending unit is going bad!!
I’ve had my 07 avalanche for years I can’t fiquire what is wrong with mine has new fuel pump and sending unit
@davidbryant5875 check the gauge wiring! or the cluster itself
@@KITS_Auto_and_Truck_Repair changed the cluster .. yea it has to be the wiring somewhere
Can you explain why you use the test light? If the two wires were shorted what would happen? Would it hurt the ECM?
Alan Gaudry very good question, the test light acts as a buffer in this case, ( kinda like a resistor ) to reduce current flow... shorting the reference wire to ground might damage the ECM or just throw a code, but its better to be on the safe side by using a test light
I have a 2008 chevy express 2500 van with code p0463 and the fuel gauge showing empty but the tank is full. Should I follow the same procedure
mohammadabid 1222 yes you most likely have the same problem... follow the steps on the video and you will be able to find your problem, you have to have a scan tool to erase the trouble codes before you start doing the tests.... Good luck!!!!
08 chevy 3500 hd cab and chasis 4x4 6.0 with dual tanks, I can trigger my gauge sweep, fuel sending unit has resistance that should indicate 15% fuel in front tank. my gauge reads empty, I am trying to find the origin of the signal to the gauge? what are the possibilities'
thanks Rich
Richard Engstrom you might have an open in the wiring!! or one of the sending units is open internally!!
I have the p0463 code on a jeep commander. However, my guage works sometimes but other times it stays on F or E. I also notice that when the check engine light is on and the guage is not correct, my reverse (backup) lights also do not work. But when the check engine light is off and my guage is right the back lights work. Does this still sound like a faulty sending unit? I had the fuel pump and sending unit changed about 13 months ago.
Ken Simek that sounds like a shared ground problem... you have to look at a wiring diagram to see where all these circuits connect, if you can't get wiring diagrams you should have someone look at it for you...
i have a same problem but it started when i was change the computer harness..my fuel pump is everything working and good but still empty indicator guage. how can i find in alots of wiring in the computer harness cause too much wiring.
Rhomel Almero you probably got the wrong harness installed...
Where are you from I need my truck fix
Colieon MacDoney I'm Located in Dickerson Maryland!!
Good job again ..
bilal flayeh thanks...
Thanks
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Nice sir Tq
Tamir Khan thanks!!!
Did you know you can use the scan tool to work the gauges
Abilio Arruda yes I do...