Resetting Check Engine light

I have a '99 Jimmy and the gas tank sensor has been bad since I bought it. The guage needle floats up and down and I usually just fill it up with gas when I hit the half-tank line. My Check Engine light pops on every once in a while and every time I get the $80 computer diagnostic the mechanic just "resets" the light (he turns it off) and he tells me it was just the fuel sensor again. To get it fixed is going to cost me a whole lot of money as the tank has to be removed etc, so I was just inquiring as to how to "reset" the check engine light myself so I can circumvent another $80 diagnostic.
My neighbor told me how his buddy did it with his Ford, by removing one of the battery terminal wires and keeping the ignition engaged for thirty seconds to reset it, but since this is a GMC, I didn't want to chance it until I got vehicle-specific information.
Thanks!

You need a scanner to check or reset the check engine light.
But
I would question the part about the fuel gauge setting the check engine light.
What code no is it setting?

Auto zone and some parts places will read the code for free.
Get the code and post back code no.

For 80$ to just reset the light the mechanic shold have gave you a repair order with the code no on it.
Check the repair order and see what was on it about the check engine light.
MT

After looking through some (well, MANY) posts on this, and other forums relating to Jimmy fuel sender failures, and seeing that the part only costs thirty bucks, would it be prudent for me to try and replace it myself? I have mediocre skills as a mechanic, but I do most of my work myself that doesn't require vast knowlege and specialized tools (i.e. brakes, rotors, calipers, ball joints, control arms & bushings, door panels, etc). My mechanic stated that him doing it would cost hundreds and hundreds of dollars, but how hard can it be? The part is so cheap it makes me want to try it myself but my Haynes manual has absolutely no information on it. I'd rather fix it than to cheese it out by simply resetting the idiot light.

You have to remove the fuel tank and fuel pump moduel to replace the sending unit.
How many miles is on the old fuel pump?

What is the code that it is setting?
You may have another problem besides the sending unit.
Get the code no and post back code no.
MT

Just a question why would you want to see a mechanic to check the light?.. Go to your local autozone or parts america and they will do it for free. It will save you some $$$... anyways. I did the fuel pump myself .. read this article. Great piece to read before you try...http://www.automotiveforums.com/vbulletin/showthread.php?t=633098

After you feel comfortable go to www.rockauto.com and purchase the pump. I say the pump since it is inevitable that this will go and I dont see the reason why just to the sender. It took me about 3 hours and being very careful. Keep in mind not to break the little vent tubes attached to the tank and lay a blanket down on the ground to prevent spark and boom... but it should go smooth.. good luck..

To answer your question, removing one of the battery cables for a few minutes will reset the on-board computer and should shut off the light. Once the battery is disconnected, I don't see any logic to leaving the ignition switch turned on as it will not have any power. Stop paying this mechanic to reset the light. As the others have stated, you can get it done for free or do it your self by removing the battery terminal.

I suspect your mechanic is ill informed.
I have had an intermittent fuel gauge for 5 years and it has never set a code. (2000 Jimmy)

Reread MT2500's post again and get the code from Autozone or similar. (for free)

You should have OBDII computer so taking battery lead loose doesn't erase the codes.

Re:the fuel gauge.
Frequently it is the flimsy wires on the plug (top of the tank), that have a break inside the insulation. (Like mine) The actual gauge on mine is fine, just haven't gotten around to replacing the pigtail.(plug and short wires)
If you have to swap the fuel pump assembly, there's a post describing it on the forum.
Meanwhile, set the trip odometer at each fill up and gas up at 300 miles. (Mileage may vary)
Good luck

Disconnecting the battery will turn the light off IF there are no hard faults, (faults in systems that the PCM monitors continously). Disconnecting the battery will not erase the codes, they remain in memory until the fault is no longer detected, or the problem is repaired. The only way to erase DTC's, (Diagnostic Trouble Codes) from the memory is with a scan tool.

The PCM runs several different monitors during each drive cycle and each drive trip. The parameters must be met exactly, or the monitor will not complete its test. When a monitor runs and the test is completed, if a fault is detected, the SES, (Service Engine Soon) light will come on. Some monitors may take a considerable amount of mileage to run and complete their test, ie EVAP system. Depending on how the vehicle is driven, it's possible for the EVAP monitor to literally take months for it to run and complete its test.

Disconnecting the battery will turn the light off IF there are no hard faults, (faults in systems that the PCM monitors continously). Disconnecting the battery will not erase the codes, they remain in memory until the fault is no longer detected, or the problem is repaired. The only way to erase DTC's, (Diagnostic Trouble Codes) from the memory is with a scan tool.

The PCM runs several different monitors during each drive cycle and each drive trip. The parameters must be met exactly, or the monitor will not complete its test. When a monitor runs and the test is completed, if a fault is detected, the SES, (Service Engine Soon) light will come on. Some monitors may take a considerable amount of mileage to run and complete their test, ie EVAP system. Depending on how the vehicle is driven, it's possible for the EVAP monitor to literally take months for it to run and complete its test.

As always, Old Master I stand corrected and bow to your knowledge.:grinyes: I was misinformed. I was under the impression that removing a battery cable reset the On-Board computer and wiped out the codes. Apparently not.

I would however give removing a battery cable a try before I plunked down $80. That's a no brainer. It seems that his concern is turning the light off.

I also agree with johnhutchinsusa. My 2000 Jimmy SLE has an erratic fuel gauge as well but there is no SES light. I do the 300 mile thing too. I suspect there are other issues here.