My treadmill is 2 days old. We turned it on and my son was walking on it, then he bumped the key string and the key fell off the magnet. When we put it back on, the treadmill was and still is stuck in the "incline" mode....all the screen says is incline with two --'s. It goes up as high as it will go, stops for a second, goes down flat, stops for a second and goes back up again. I took off the hood and made sure the magnet was aligned with the pulley. I unplugged it, I hit reset, I unplugged the console from the wire in the upright, I have tried all of these things in every different order I could think of and it will not stop! No buttons work at all! I cannot even think of having to load this up and sending back to QVC! I hope you have an easy quick fix, I would be forever indebted to you. thanks for your time. Leah

Hello. In the mean time you can use a fridge magnet to get you back on the machine. You might need a strong magnet, so if the first one doesn't work keep trying.
try googling the brand of machine you have to purchase parts or try eBay under treadmill safety keys.

GymWorld.net.au

is it a little round read magnet with a string? try a round magnet of your own and see if that works

you need to Run THE SOFTWARE CALIBRATION for easy diagnostic and repair.
This happen because the speed sensor is bad-adjustment, need to calibration.
God bless you

Renee, Here is how to recalibrate the incline motor. Read all of it It will be good to keep.
Plug in your treadmill, do not stand on the walking belt. Hold down the "Stop" and "Speed +" key and insert the safety key or magnet, let go of the two keys. Now press "Stop" key once. This puts you into the level 2 of calibration. Press the "Speed +" key slowly until you see 85 on the console, (at this point the display is going to show the percentage of motor usage and also the actual walking belt speed) at 85% motor usage your top speed should be between 10 and 10.5 MPH or (of 12 and 12.5) depending on the treadmill. You must know your treadmills top speed. (Important the motor may be damaged if you set the maximum speed higher than the maximum speed that your treadmill is made for). If the speed is higher than 10.5 or 12.5 then you need to turn the potentiometer down to the correct level. If the speed it to low you need to turn the potentiometer higher. Once the speed is correct you are done calibrating the speed. Press the (-) speed key to lower the percentage to (0). Next press the incline (+) button, this will make the incline motor go all the way to the maximum incline and come all the way down to the level position. Then remove the safety key and the treadmill will reset into the normal manual mode, when you re-insert the safety key. Matt

If you need further help, I’m available over the phone at https://www.6ya.com/expert/matt_8dbc24bf722649ac

How to Troubleshoot a Nordic Track C2500 X Jolie Johnson

Based in Austin, Texas, Jolie Johnson has been in the fitness industry for over 12 years and has been writing fitness-related articles since 2008 for various websites. She received her Bachelor of Arts in English and philosophy from the University of Illinois.
By Jolie Johnson, eHow Contributor

updated April 15, 2011

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The NordicTrack is a treadmill designed for in-home use. It offers a speed range of 0 to 10 mph and an incline range of 0 to 10 percent. It folds up vertically to save space when you aren't working out and can be rolled to a different room. The console has 16 preset workout programs and features iFit interactive technology. If you have problems with the console or walking belt, you can often fix them yourself with some basic troubleshooting steps
Instructions

1. Power Turns Off When You're Using the Treadmill
   • 1 Check the reset switch on the bottom of the treadmill near the power cord. If it has tripped, the top of the switch will protrude. Wait 5 minutes then press the switch.
     
   • 2 Check that the power cord is plugged in completely. If it is plugged in, unplug it, wait 5 minutes then plug it back in.
     
   • 3 Remove the magnetic key from the console then reinsert it.
     
   The Console Won't Turn Off
   • 1 Insert the magnetic key into the console. Your C2500 is stuck in demo mode if the console won't turn off after you remove the magnetic key from the console.
     
   • 2 Hold the "Stop" button down for a few seconds.
     
   • 3 Press the "Speed" down (-) button. Remove the magnetic key.
     
   The Incline Does Not Change Correctly
   • 1 Press and hold the "Stop" and the "Speed" up (+) button. While holding the buttons, insert the key into the console, then release the buttons.
     
   • 2 Press either the "Incline" up or down arrow button. Wait while the incline raises and lowers. This recalibrates the incline system.
     
   • 3 Remove the key from the console.
     
   Walking Belt Slows
   • 1 Unplug your C2500 and remove the key from the console.
     
   • 2 Turn both rear adjustment bolts, located on the back of the walking deck, to the left, a 1/4 turn.
     
   • 3 Lift the edge of the walking belt in the middle of the deck. You should be able to lift it 2 to 3 inches off the walking platform. If the belt is still too tight, loosen the bolts another 1/4 turn each.
     
   • 4 Plug the treadmill in and reinsert the console key. Walk on the belt at a slow speed to see if it still slows. Repeat Step 2 if necessary.
     

If the walking belt is off-center, first remove the key and UNPLUG THE POWER CORD. If the walking belt has shifted to the left, use the allen wrench to turn the left rear roller bolt clockwise 1/2 of a turn; if the walking belt has shifted to the right, turn the bolt counterclockwise 1/2 of a turn. Be careful not to overtighten the walking belt. Plug in the power cord, insert the key and run the treadmill for a few minutes. Repeat until the walking belt is centered.

If the walking belt slips when walked on, first remove the key and UNPLUG THE POWER CORD. Using the hex key, turn both rear roller bolts clockwise, 1/4 of a turn. When the walking belt is correctly tightened, you should be able to lift each edge of the walking belt 2 to 3 in. (5 to 7 cm) above the walking platform. Be careful to keep the walking belt centered. Then, plug in the power cord, insert the key, and carefully walk on the treadmill for a few minutes. Repeat until the walking belt is properly tightened.If you still have slipping then the drive belt under the motor shroud can also cause this problem unplug unit remove shroud then plug unit in start it up observe the front roller to see if it stops if it does locate the tension adjusting bolt by the motor loosen motor mount and proceed adjusting until slipping has been eliminated

If the walking belt slips when walked on, first remove the key and UNPLUG THE POWER CORD. Using the hex key, turn both rear roller bolts clockwise, 1/4 of a turn. When the walking belt is correctly tightened, you should be able to lift each edge of the walking belt 2 to 3 inches above the walking platform. Be careful to keep the walking belt centered. Then, plug in the power cord, insert the key, and carefully walk on the treadmill for a few minutes. Repeat until the walking belt is properly tightened. Now if this does not solve this problem then check the drive belt and adjust accordingly, also reverse the process of the above mentioned

Trimline treadmill starts up then code E2 comes up, and the display shuts down. 
Any ideas???

you can use eny magnet, and if you need the string you can epoxy glue it to the magnet you are using