LB7 2003 fuel gauge problem/questions

[six5creed]

My 2003 dmax fuel gauge went to empty about three months ago and light stays on. I done some reading and ordered the stepper motor. Waiting for it to arrive my check engine light came on a few times when I plug truck up when it gets really cold and gives the temp sensor something code. When the check engine light comes on the fuel gauge started working but went to full. I know the tank was about 1/2 full and it stayed on full. When the check engine light would go off the gauge would read empty and light comes on. I replaced stepper motor today and it stays on empty still. The gauge will move about an 1/8" when key is cycled for cranking before and after motor replacement. Is it the sending unit in the tank or do I have something else going on? Does anyone have a used sending unit I could try if that's what it is before I buy one for $300+? I also unhooked the wire from sending unit and it made no difference. I read somewhere if you unhook the wire the gauge should read full and if it doesn't it's probably the stepper motor. Not true in my case if that is the case.

 

[motoking_1990]

Mine does the same thing. Mine gradually got worse. Now it stays off unless it's full. I replaced the stepper, no change. The lb7 level sender is molded into the unit. You can buy the whole unit for 300 or something or you can use a doorman and fab a new one in for $20. I'm about to do this to my truck. I'm waiting on my back ordered beans sump first. I will find the link for the level sender fix.

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[motoking_1990]

Here is that how to if your interested.

http://www.dieselplace.com/forum/71...iews/421416-how-fix-your-fuel-gauge-30-a.html


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[THEFERMANATOR]

A heads up, the stepper motor has NO control over the low fuel light. So if it comes on, it's not the stepper motor. Sounds like your sender has gone out in the tank. The ECM reads the fuel level from the sender, and sends out the tank amount over the J1850 bus where the cluster reads it, and dispalys it on the gauge. If the light comes on and it reads empty, it is because the ECM is telling it that it is empty. Also if you fill the truck with it running, it will go to empty as the ECM will think something is wrong with the sender, or if the readings go haywire or all over the place from the tank, it will default to empty as a safety measure.

 

[motoking_1990]

At least it's an 03 and not 01-02.

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[THEFERMANATOR]

At least it's an 03 and not 01-02.

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Why is an 03 better than an 01-02? They both use the same logic for the gauge, and the same sender in the tank. 02- used air core motors instead of steppers, and air cores rarely fail unlike 03-05 steppers that fail all the time.

 

[six5creed]

Here is that how to if your interested.

http://www.dieselplace.com/forum/71...iews/421416-how-fix-your-fuel-gauge-30-a.html


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Thanks for the info and the link. I will check into that as well.

 

[six5creed]

A heads up, the stepper motor has NO control over the low fuel light. So if it comes on, it's not the stepper motor. Sounds like your sender has gone out in the tank. The ECM reads the fuel level from the sender, and sends out the tank amount over the J1850 bus where the cluster reads it, and dispalys it on the gauge. If the light comes on and it reads empty, it is because the ECM is telling it that it is empty. Also if you fill the truck with it running, it will go to empty as the ECM will think something is wrong with the sender, or if the readings go haywire or all over the place from the tank, it will default to empty as a safety measure.

Thanks for the info here too. I figured the stepper motor was the cheapest place to start, a man can dream can't he? Lol. I kinda figured it was the sending unit to start with then got to reading all the things about bad stepper motors so figured I would try it first. Drives me crazy with the gauge on empty and the light on.

 

[NC-smokinlmm]

Needs a sender...

 

[six5creed]

After marking the needles at the counter clockwise rest position I was having trouble getting the needles off. Two teaspoons worked great.

 

[motoking_1990]

Did the stepper fix your issue?

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[six5creed]

Did the stepper fix your issue?

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No, it's my sending unit in my tank. Stepper was cheapest place to start. You get yours fixed?

 

[motoking_1990]

No not yet. Beans is still on back order. I'm going to be pulling my bed installing the Beans, doing the sender, installing my drop shackles, and doing some frame restoration getting rid of surface rust. It will be my yearly winter project. I always look forward to it.

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[motoking_1990]

I had a feeling it was the sender. Like Ferm said the ecu gets the signal and sends the messages through class 2 (J1850) to the DIC and the stepper. If it were the stepper the message display would still work and the stepper would be wrong.

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[six5creed]

I recently had my bed off installing a gooseneck hitch I made but unfortunately funds weren't available to get a sending unit to put in at that time. It was nice to take a wire brush and hit the surface rust and put some fresh black paint on though.

 

[motoking_1990]

I recently had my bed off installing a gooseneck hitch I made but unfortunately funds weren't available to get a sending unit to put in at that time. It was nice to take a wire brush and hit the surface rust and put some fresh black paint on though.

That's what I am wanting to do. It's not really bad but it doesn't have that clean look I want.

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[thneill]

I know its a little old but my 03 is having dash issues too...

Oil Pressure is dead but will every once in a while read correct, not sure if its the sensor or the cluster.

Battery volts doesn't read either, i think its pegged as far as it can go.

and the Fuel gauge just messed up the other day. its like it shifted 1/4 tank to the right (full now reads off the gauge a bit passed the full mark).

Im thinking its the cluster but any thoughts would be greatly appreciated.

Also, speedometer seems a bit jumpy, not bad but noticeable.

 

[THEFERMANATOR]

If the oil pressure reads low without a low oil pressure warning, then its most likely a bad stepper. When steppers go they normally start off jumpy, then peg out, but if the gears skip, they can go off a 1/4 or so. If the whole cluster goes out, then you normally have a failed power supply or broken solder issue at the power supply.