98 Yukon gas gauge problem

[rayninglead]

First post and my first Yukon and I love it everything works except the gas gauge and the blend door is broke ( I think ) I've been researching all day and don't know where to start. I've had the truck for a week and the gauge goes back and fourth from empty to full randomly and it's always either way empty or full . hasn't stopped doing this since I've got it. until this morning it stopped and stayed at 1/4 for a couple minutes then went crazy again. I don't know where to start with this one any help would be great.

 

[SunlitComet]

Access to a multimeter or ohmmeter have you?

 

[rayninglead]

Yes I do just don't know really where to start seems like this is very common. And there's no real straightforward fix

 

[SunlitComet]

Well if this happens with the vehicle stationary you can starts by probing the #13 wire on the C3connector of the pcm while power is off it is a purple wire with a white strip. probe that wire with other test lead to good ground. Measure in ohms. Should have 90ohm on a fuel tank and near 0 on an empty tank. while testing this rock the vehicle a bit and see how far off the reading go. If it gets real wild then the sender in the tank is at fault. Also while the C3 turn the key on and see how the gauge works then if it is still crazy it is likely the pcm is defective.

 

[rayninglead]

Omg thanks so much will let you know in a few how it turns out

 

[rayninglead]

Where is the connector located? Under hood on driver side fender? If so which one is it? Don't want to disconnect if I don't have to.

 

[SunlitComet]

It is on the pcm under the hood you should have 4 of them on there. You are looking for the one that has the word "clear" next to it on the pcm.