The treadmill shuts down and the screan says speed error 12

Here are some possible causes and solutions:

Overheating: If the motor or electronics of the treadmill get too hot, the machine may shut down to prevent damage. Make sure that the treadmill is placed in a well-ventilated area and that the air filters are clean. You can also try lubricating the walking belt to reduce friction.

Faulty speed sensor: If the speed sensor is malfunctioning, it may cause the treadmill to shut down. You can try cleaning the speed sensor with a soft cloth and see if that helps .

Worn walking belt: If the walking belt is worn or damaged, it may cause the treadmill to shut down. You can try replacing the walking belt and see if that helps.

Electrical issues: If there are any electrical issues with the treadmill, it may cause the machine to shut down. You can try resetting the circuit breaker or unplugging the treadmill for a few minutes and then plugging it back in.

If none of these solutions work, it may be best to contact Proform customer service.

With belt movement check speed sensor. Without belt movement check MCB. If you neglected unit it could be belt and deck if its shutting down during a workout. I have also see a lot of on/ off switches getting old and causing LS errors due to low voltage to MCB

Dear Sir:

Thank you by your request. I hope everything is o.k

Now I will try to help you.

You have electrical-mechanical Problem:

If you can walk on your treadmill but it shuts down during a workout, it is normally caused by a friction problem with the belt and deck.
Here are the most common symptoms and solutions:
Symptom: The treadmill operates for a given period of time and the circuit breaker on the treadmill trips causing you to have to reset the breaker, or let it cool off then reset the breaker. The
amount of time required to shut down will progressively get shorter.
Solution: The walking belt is worn. The incline test is the best test for it if you don't have a way to take a
DC amp draw. Put the treadmill at full incline and walk normally. If it takes it longer to shut off or does not
shut off at all, you need to replace the walking belt. Be sure to inspect the deck for wear too. If you want to
go for a cheap fix try lubricating the walking belt. The best fix is to replace the
walking belt and then regularly maintain it and keep the treadmill clean.

Symptom: The treadmill will show power but after a given period of time, the treadmill will simply shut
down. Once you let it cool off, you can restart it back up but it shuts down faster and the time required
before it shuts down gets progressively shorter.
Solution: Your treadmill is most likely equipped with a heat sensor which shuts down the motor and/or
electronics to prevent them from burning up. If this is the case, replace the walking belt. Be sure to inspect
the deck for wear too. If you want to go for a cheap fix (that we don't recommend) try lubricating the walking
belt. The best fix is to replace the walking belt and then regularly maintain it and keep the treadmill clean.

Symptom: The treadmill shuts down in an intermittent pattern...there is no rhyme or reason to when it will
shut down. I get an error code or nothing shows up on the panel. I have to either unplug the treadmill or
reset it to restart the treadmill.
Solution: If you get an error code, contact us with the code and make and model and we will try to help
you figure out what is going on. Typically we either find a loose wire, an intermittent short, a bad power
board, or a bad control panel in service calls that we do locally. Unplug your treadmill and then check all
your wiring to make sure nothing is pinched, crimped or loose. Remove and replace each connector in
case corrosion is causing the problem. If the problem persists, you most likely have a bad control panel or
some call it a console.

Thank you in advance, sincerely. God bless you.

If you need additional Help , please contact me.

E.CUADRA
MANAGUA, NICARAGUA. C.A.

The motor controller weakens over time because of the excessive amperage draw of the motor do to lack of lubrication (which wears the walk belt and walking deck).

Take an amperage reading of the motor it should be 2-3 amps with no one on it, with someone walking on it it should be around 6-12 amps. I would bet yours is elevated above 6-12 amps.The controller is dropping output because of the friction problem.

The first thing to try after testing the amperage is to lubricate the walking platform. Then retest and see if the amperage comes down and it doesn't shut off.

If it does then the next step would be to replace the walking deck. If the amperage still is up you may need to replace the walk belt second and finally if after replacing the deck and belt, if the unit is still shutting down replace the motor controller.

E21 means the treadmill is not picking up a speed signal once the start key is pressed. First, determine if the motor is turning before you get the E21 or not. If the motor turns, the speed sensor is the most likely problem. If it does not, you can manually turn the belt with your feet before you get the E21 and you should get a speed reading but eventually you will get an error code because it is almost impossible to keep the speed constant enough for the computer. Try running it through calibration with the motor shroud off.
Press the Stop and the Speed Up keys down while inserting the safety key.
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.
Press either incline key and the incline will calibrate automatically.
On this next step do not step on the treadmill when you 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 black square with a white center and is located near the three small speed wire connections 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.
If the motor does not run, test the motor but first unplug unit then unplug the two leads ( Red and Black ) that is connected to the Motor Control Board.Cordless drill battery- get a fully-charged, 18 volt (preferred) cordless drill battery and on most treadmills connect the red and black motor leads to the battery (some have different colors but if you have two wires and get it hooked up backwards, the motor will just run backwards and won’t be harmed). If good, the motor should operate at about 1 MPH. Then Motor Control Motor will need to replaced

Info from PDF files located on Sportcrafts website under manuals.
E3 – No speed sensor reading. Unit shuts down. This is the most difficult repair diagnose. The speed
sensor is connected to the frame of the treadmill near the drive pulley on the front roller. There is a
small magnet on the side of the pulley wheel. The sensor tip must be no more than 5mm from the
magnet. If for any reason the distance is greater than 5mm the treadmill will shutdown
Adjust or replace speed sensor.
Treadmill: Speed Sensor Replacement
1. Make sure your treadmill is unplugged before you begin.
2. Remove the motor cover located in the front of your treadmill, it is held on by a few screws.
3. Locate your speed sensor; it is the small T shaped part with a red and black wire coming from it.
4. Remove the 2 screws in the speed sensor and remove the old sensor.
5. Place the adjustment holder on the frame with the open holes facing the pulley wheel, the prongs facing
up and way from the pulley wheel. Insert the screws but don’t tighten fully.
6. Now place the speed sensor over the prongs with the square part facing the pulley wheel and the red and
black wire to the far right.
7. Plug the treadmill back in and slide the speed sensor until it is 5mm from the magnet inside the pulley
wheel, you may have to do this several times until you can position it so it no longer shuts down. Use 2
nickels to figure out the spacing. The width of 2 nickels is 5mm.
8. Once you find the correct position tighten the screws all the way; being careful not to touch any of the other electronics
9. Place the motor cover back on and enjoy your machine.

Call manufactor for calibration procedure. If this doesnt work, you will probably need a lower board.

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