Gas needle grops back to empty and check gages light comes on what could be problem

You could use two resistors, Two different ohms specs for full and empty. Place resistor between proper wire colors in diagram. Turn on the key, If gage reacts properly to full and empty resistors, then I think the problem is the sending unit in gas tank. If not, the problem could be almost anywhere, wiring circuit--pcm--instrument cluster. I did see trouble codes relating to fuel gage sending unit. I hesitate to get into that? good luck

Map sensor is bad

Most of the time it is a open circuit in the fuel level sensor.It located in the tank.

I hope you did not top it off because filing it up like that will wreck havoc on the evap system. The engine light should go away as the gas in your tank is used up, or it may take some time, but hopefully it goes away. Just next time you fill up don't top off when it clicks off thats it. Also make sure the gas cap is tight. A loose gas cap can make the check engine light come on. I am an emmission repair specialist, and deals with these crazy things sometimes lol.

i have the same problem and it will cost to have it fixed.but right now we are using our trip odometer by 1st fulling up and refueling at 300 miles then resetting.as far as the check engine it could be as smple as a lose gascap. go to advance auto parts and ask them to check it.they will do it for free.if you buy the part from them you can take it back and they will clear your codes.hopes this helps you get by for a while

u need to change this gauge or try to dissasseble and clean it very well then try to install it back again

Is......the problem--"the gas gage reads empty when there is fuel in the tank. OR, The gage moves when the key to turned off ?

If it's the first,
You will need to test the gage and through process of elimination, determin if the Sending unit inside the fuel tank has gone Bad.

If its the second ? - Electrical gauges will move when powered down. Normal

Testing the gauge may not be easy - just depends on your ability.
It is a simple 2-wire gauge circuit, when disconnect (usually need the fuel tank) the gage reads in one direction (either full or empty)
then when shorted-the gage reads in oppisite direction.

Of course you must select the correct wires or you may short out the wrong circuits!! Most GM vehicles use a purple wire & black wire.

A quick method I have used to check the in-take part of the gauge is this.
1st. know there is gas - 1/2 tank works best.
2nd driver's door open, key in run position, engine not running.
3rd gently lift up on the door then let if come back down, gently.
just enough to cause the gas to slosh around.
4th - keep an eye on the gas gage, a bad sending unit in the take will show up as a "twitchy" needle.

Of course, if the gage never leaves empty - sloshing won't work.
I have a known good sending unit I can plug into the vehicle and simulate different levels of fuel - if the gas gage works, I know the problem is in the tank.

Let us know.

Dave

this is a faulty fuel level sensor. it can be replaced seperate from the pump assembly . tank will have to come out to repair

Yes it is all one unit, and yes that is what the problem is. don't use aftermarket parts, use OEM, (Delco Remy) they are much better quality.

you gas tank float tells you weather your empty or full. it sound like it is stuck. you might need to replace the float to get you gas gage working again.