Thread: Fuel gauge nightmare

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  1. #21 Re: Fuel gauge nightmare 
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    Quote Originally Posted by PK2000GT View Post
    Damn, my 2000 GT does the same. I have a buddy who is a master tech and he said I could use his brand new bad ass cpu reader to find out where the problem is. When I find out, I will share my info with you all too.
    The CPU reader will likely tell you you are getting codes to several sensors, but DO NOT start swapping sensors willy nilly, just because you see a code with its name in it. The sensor or sensors could be fine, and the problem could be something else associated with it, like a lack of voltage to it. THINK about WHY you are getting codes all of a sudden on several things. Is there a common root cause? Then get hold of and electrical diagram and trace things out, see whats common to the sensors in question. You may also by doing a google search on the sensor name, come up with how tos on checking the sensor itself with a multimeter either in or out of the car. If I just blindly replaced every sensor that threw a code on the problem I just went through, I would be out well over a hundred bucks (even more if a shop was doing the work, and they , unfortunately also tend be sensor swap happy), and still have my problem will all new sensors. The total material cost to fix my problem, because I checked the cheap stuff (wiring) first, ended up being less than a penny for several inches of black plastic electrical tape. I actually spent most of my time solving this problem by researching what the codes I was seeing meant, looking at the wiring diagram to see how they could be related, and thinking about what might be causing them all to be thrown together. Actual time between first popping the hood to fix things, and finding the source (the pinched wire on the TPS), after I did all the thinking part of the job, was less than ten minutes. I'm not saying all of these types of fixes are that easy, but THINKING rather than just REACTING to a badass CPU reader display is the way to go.
    Last edited by AJ1G; 02-03-2013 at 12:23 PM.
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  2. #22 Re: Fuel gauge nightmare 
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    My gas gauge goes up when I'm accelerating and if I just sit there idleing it will read correct no check engine light either what could this be?
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  3. #23 Re: Fuel gauge nightmare 
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    Quote Originally Posted by kawasakidrivinghick View Post
    My gas gauge goes up when I'm accelerating and if I just sit there idleing it will read correct no check engine light either what could this be?
    ALL vehicle gas gauges, to some extent, will do this. The level is measured by a float (think fishing bobber) that floats on the surface of the gas in the tank, and is mechanically connected to a wiper on a variable resistor (think shaft of an old school type radio volume control) that changes the voltage sent to the gauge circuit in proportion to the position of the float, which of course is a function of the level of gas in the tank. As the car accelerates, the gas sloshes around in the tank, and moves the float level around. Unless you are seeing huge changes in indication, like the level jumping all the way to full when the tank is almost empty, sounds normal. transient changes on the order of 1/8 to a 1/4 tank are not uncommon. What matters is where is sits when you are running hot straight and normal....
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  4. #24 Re: Fuel gauge nightmare 
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    it does it sitting still it goes from empty to full
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  5. #25 Re: Fuel gauge nightmare 
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    Quote Originally Posted by kawasakidrivinghick View Post
    it does it sitting still it goes from empty to full
    If its doing this and is not throwing any OBDII Codes such as the P1635 5V REF A LOW (voltage), then the problem most likely is associated with the tank level sensor or the sensor wiring to the PCM. Check the wiring first!
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  6. #26 Re: Fuel gauge nightmare 
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    No codes and what wires do I check
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  7. #27 Re: Fuel gauge nightmare 
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    Alright...after plugging computer into cpu, I found one code: p0463 and it happens to be my fuel pump sensor. So, in two weeks she is going under the knife.
    ...A gear-head in my own way...
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  8. #28 Re: Fuel gauge nightmare 
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    Quote Originally Posted by kawasakidrivinghick View Post
    No codes and what wires do I check
    The wires going to the fuel tank's sensor, at the sensor. I don't have a manual handy at this point, suggest you get a copy of the schematic through Autozone's online manual service, you have to be registered with them but its free. I sense that you are not too electrically savvy, suggest you try to get someone with an electrical background to help you, if possible avoid using a dealership or repair shop, chasing electrical issues is usually not their forte, they tend to throw replaceable parts at problems rather than doing real troubleshooting that includes understanding what voltages and resistances should be on specific points of the circuit. And time is big money with them as well.
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  9. #29 Re: Fuel gauge nightmare 
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    Quote Originally Posted by PK2000GT View Post
    Alright...after plugging computer into cpu, I found one code: p0463 and it happens to be my fuel pump sensor. So, in two weeks she is going under the knife.
    Don't pay for a new sensor until whomever works on it has verified that the wiring between the sensor and the voltage supplied to the sensor is correct, and that the original sensor is in fact defective. A simple resistance check of the sensor with an ohmmeter will take only a minute after gaining access to it, you do not even have to remove it from the tank to check it. If possible, tell whoever is doing the work that you will authorize doing the work to actually remove and replace the sensor only after he has actually verified that the problem is not the external wiring to the PCM or that the sensor failed a resistance check with it installed in the tank. If they don't agree to this than go find someone else who knows how to properly troubleshoot electrical issues.
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  10. #30 Re: Fuel gauge nightmare 
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    Quote Originally Posted by AJ1G View Post
    Don't pay for a new sensor until whomever works on it has verified that the wiring between the sensor and the voltage supplied to the sensor is correct, and that the original sensor is in fact defective. A simple resistance check of the sensor with an ohmmeter will take only a minute after gaining access to it, you do not even have to remove it from the tank to check it. If possible, tell whoever is doing the work that you will authorize doing the work to actually remove and replace the sensor only after he has actually verified that the problem is not the external wiring to the PCM or that the sensor failed a resistance check with it installed in the tank. If they don't agree to this than go find someone else who knows how to properly troubleshoot electrical issues.

    There is a very in depth discussion of this issue in the P0463 code up in the Check Engine Light Trouble Codes Sticky posting in the start of the General Tech Discussion threads listing. Everyone should read about what could cause a particular code in this reference material before doing anything else! P0463 Sensor level high could indeed be caused by a failed (open circuited) sensor, but it could also be due do to a broken wire or a dirty (high resistance) connection in the wiring connector at the sensor. Since you problem seems to come and go, the latter might be the case, but the sensors themselves can also go intermittent. By Sensor Level High they mean the voltage returned from the sensor that is measured at the CPM is higher than normal, this would be caused by not enough resistance from the sensor to pull the voltage down to the expected range. If there is about 5 volts between the two leads coming from the PCM to the sensor at the connector with the connector removed from the sensor itself with the ignition on, then wiring is likely OK.
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  11. #31 Re: Fuel gauge nightmare 
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    i dont have a code on my car. so i check the the voltage coming to the pump?
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  12. #32 Re: Fuel gauge nightmare 
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    Quote Originally Posted by AJ1G View Post
    Don't pay for a new sensor until whomever works on it has verified that the wiring between the sensor and the voltage supplied to the sensor is correct, and that the original sensor is in fact defective. A simple resistance check of the sensor with an ohmmeter will take only a minute after gaining access to it, you do not even have to remove it from the tank to check it. If possible, tell whoever is doing the work that you will authorize doing the work to actually remove and replace the sensor only after he has actually verified that the problem is not the external wiring to the PCM or that the sensor failed a resistance check with it installed in the tank. If they don't agree to this than go find someone else who knows how to properly troubleshoot electrical issues.
    Thanks for the advise. I will talk with my tech who is also by best friend for over 12 years. He will do what I say and suggest, lol.
    ...A gear-head in my own way...
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  13. #33 Re: Fuel gauge nightmare 
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    Quote Originally Posted by kawasakidrivinghick View Post
    i dont have a code on my car. so i check the the voltage coming to the pump?
    At the fuel pump level sensor connectors on top of the gas tank (accessible from the trunk, or the back seat pass through door, check for 5V between a purple and black wire on the connector going back to the engne control module, with the key on and the connectorunplugged - should see 5V DC thre if the wiring is good....
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  14. #34 Re: Fuel gauge nightmare 
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    Quote Originally Posted by AJ1G View Post
    At the fuel pump level sensor connectors on top of the gas tank (accessible from the trunk, or the back seat pass through door, check for 5V between a purple and black wire on the connector going back to the engne control module, with the key on and the connectorunplugged - should see 5V DC thre if the wiring is good....
    BTW, I got this info from the schematics that are available through Autozone's web site - they are EXCELLENT!
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  15. #35 Re: Fuel gauge nightmare 
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    I to am having this same problem but the car want run when the gauge acts up and its at opt temp constantly jumps F to E and you can hear the fuel pump relay clicking on and off while gauge is all over the place. Anymore info here on what was wrong?
    Girlfriend's ride: 03 Summit White Grand Prix GT 180* T-stat, Autolites, Bosch wires, Custom CAI
    My Rides: 2006 LBZ CCSB LT3 Duramax Diesel Puller/DD
    2002 LB7 Duramax Diesel CCSB LT3 to many mods to list! Work Truck/DD
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