While running the treadmill will automatically speed up and the incline will automatically rise

To initiate the calibration routine, hold down the SPEED +
button and the SPEED - button simultaneously for three seconds. During the calibration routine, the INCLINE
TRAINER will automatically rise to the highest incline level and then return to the lowest incline level.

P.S. This is listed in your user manual in the "Troubleshooting" section if you don't have a user manual then you can get a pdf copy of it here
http://www.ereplacementparts.com/images/nordictrack/CTK59020.pdf

You must tried again the s.calibration, for easy diagnose, and troubleshooting.
However you must Adjust the speed sensor, test it, clean it, and tight any plug or connector, see the diagrams attached and proceed according.
2) Lube the elevation motor, the shaft + gear, test the motor itself for open or short. see the diagram attached. If you machine use RELAIS test it for dirty, or open and repair.
God bless you

RUN the software calibration INMEDIATELY, for diagnose, troubleshooting and fix it.

sincerely. God bless you

Add incline. Instead of keeping the treadmill on a flat surface, maintain an incline as you walk, jog or run. This will serve to replicate the wind resistance and terrain variation that you encounter when you run outdoors. Keep an incline of at least 1.5 percent on your treadmill throughout your workout.

2 Increase your speed. If you run at the same speed every time you workout, your body will not be challenged and you may reach a fitness plateau. Up your speed by a quarter-mile per hour every few weeks.

3 Vary your workout time. In order to challenge your body in different ways, variety is key. If you run for half an hour three times a week, opt for a one-hour run for your fourth workout. This will help to condition your body for endurance training, resulting in more calories burned.

4 Use intervals. Interval training can dramatically increase your calorie burn in an average workout. Instead of running at a steady pace for your entire workout, mix in sprints. Jog at a steady pace for two minutes, and then increase your speed to a full sprint for 30 seconds. Return to the steady pace to recover. Your heart rate will rise on your intense sprint intervals and stabilize on your longer recovery periods.

5 Incorporate incline into your interval training. You can use incline in the same manner that you would speed to interval train. Walk or jog at a 5 percent incline for two minutes. Increase the incline to 10 percent for two minutes and then to the 15 percent maximum for one minute. Decrease the incline back to 10 percent for two minutes and finally back to 5 percent for two minutes. Repeat this same pyramid interval a few times.

6 Wear a heart rate monitor. This will monitor how hard you are actually working as well as how many calories you burn in each workout. You can then adjust your speed and incline accordingly to maximize your calorie burn.

7 Drink plenty of water before, during and after your treadmill workout. If you are dehydrated, you won't perform as well as you can. You'll work harder and burn more calories if you're hydrated

Your owners manual describes how to perform an incline calibration. Here are the instructions.
Start the machine running. Press and hold the incline up button. While the numbers are changing, remove the safety key. Reinstall the safety key. The treadmill should rise to maximum incline, then lower to minimum. After completing the cycle, the treadmill should function correctly.
If not, you may have a damaged wiring harness (caused during assembly) or a defective incline sensor.
If the sensor is defective, you will need to replace the incline motor.

how long have you had this treadmill? usually when the hash marks appear it means that the console control board is not recognizing the incline motor. even though it does run a little bit that is just the basic test that the treadmill starts but resets after it does not sense the incline motor. These motors rarely go bad so it is more than likely your motor controller that is causing the issue. I have seen this case many times as i am a fitness repair technician. The motor controller fixes the issue 9 times out of 10

ICON CALIBRATION INSTRUCTIONS- INCLINE
1) Press the Stop and the Speed Up keys down while inserting the safety key.
2) Press the Stop key one time. The Time window should read EP:2P. Some newer models may also say FP, Pass, or the like. This means that it passes the EPROM test.
3) Press either incline key and the incline will calibrate automatically.
4) THIS IS A VERY IMPORTANT STEP BECAUSE YOU WILL GET AN ERROR MESSAGE IF THIS STEP IS SKIPPED.After completing calibration of incline, press the Stop key and then remove the safety key.



If the incline moves but you it will not operate normally nor calibrate, check the wiring from the incline sensor to the power board. If all looks normal, put it back in calibration and see if you see a blinking “- -” symbol in the incline window when you are calibrating. If not, the incline sensor is bad.

If the incline moves but only just a bit, it could be a problem as simple as the gearbox on the motor being jammed. We remove the motor from the treadmill, reconnect the wiring, and then try to run the incline motor outside the treadmill. Many times, this will unjam it if that is the problem and then reinstalling it in the treadmill will get it to work. If you have the same problem or it doesn’t run outside the machine and you can hear it try to work, you need to replace the incline motor.

If the incline motor does not move, we need to figure out if the motor is getting voltage. Use a simple multi-meter and set it to AC volts. When you put it into calibration, it tries to calibrate the directions one at a time. Measure across the white and black wires first, then measure across the white and red wires second. If the motor is getting voltage you will read 120VAC (or
thereabouts) one one of the measurements. If you have voltage but the motor won't move, you need to replace the motor.
4.
If the incline motor does not move and you have done the voltage test and you do not have any voltage present, there is a problem in the electronics board that supplies the power. If the console is powering the drive motor as normal, you can bet it is getting an incline signal and the power board needs to be replaced (some models have an integrated power board/controller) so if there is only a single board the whole board has to be replaced. It is possible the console is not giving the proper signal but we've never seen it happen in thousands of treadmills.

Unplug unit remove motor shroud then start calibration procedure.
Press the Stop and the Speed Up keys down while inserting the safety key. If you cannot get into calibration then upper console needs to be replaced.
Press the Stop key one time. The Time window should read EP:2P. Some newer models may also say FP, Pass, or the like. This means that it passes the EPROM test. At this point if it show 2F FF or Fail then upper console needs to be replaced.
Press either incline key and the incline will calibrate automatically
BE CAREFUL, THE TREADMILL WILL RUN AT FULL SPEED IN THIS NEXT MODE! DO NOT STAND ON WALKING BELT.
Press the Speed Up key and hold it down until 85 is shown in the Distance window (some models may show the 85 number in another window).
If the top speed of the treadmill does not match the displayed speed on the computer console, adjust the max speed potentiometer (pot) on the motor control board. This is the board that the red and black motor wires connect directly into in the motor area. The Max Speed pot is clearly labeled.
The max speed potentiometer is a small square with a mobile center and is located in one corner of the board and is labeled MAX SPD. It is near the harness that carries the speed signal labeled H,W,L. Using a small insulated screwdriver adjust this potentiometer clockwise to speed up and counter-clockwise to slow down the max speed of the treadmill. A tiny turn of this potentiometer will make a big difference in speed so be careful when making adjustments.
It is not important to get the speed set exactly at the max speed of the treadmill but do make sure to get the speed within .2 MPH of the max speed of the treadmill. For instance if the max speed of the treadmill is 10 MPH, make sure to have the speed set between 9.8 MPH and 10.2 MPH. Some models have a 12 MPH top speed, so please check your manual if you aren’t sure.
After completing calibration of the speed, press the Speed Down key. The treadmill will automatically return to 0 MPH. Please allow the unit to stop completely before continuing.
Press the Stop key once and remove the safety key.

Try Re-Calibrating 1st, here's how.
With the Treadmill off, press and HOLD the SPEED UP & STOP
keys, while holding the speed up & stop keys insert the Safety key (Magnet) release the speed up & stop keys. now press and release the stop key. now press the "incline up key" let the treadmill go to max incline,after it stops press and hold the "incline down key" let it go to minimum (completely lowered) you should now be re-calibrated.

With the key in the console, press one of the incline buttons. While the incline is changing, remove the key. After a few seconds reinsert the key. The treadmill will automatically rise to the maximum incline level and then return to the minimum level. Thi will recalibrate the incline system.