Why is error 3 coming up treadmill works for a few seconds then stops and error 3 comes on

SOURCE: I have a Sears Pro Form 730si. The treadmill

I believe E4 on ths 730si means that the speed of the motor the sensor is detecting is greater than the set speed. E2 would be the opposite. I believe there is a way to calibrate the speed. Look at the smaller motor controller board.

SOURCE: TX 4.9 sportcraft treadmill

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.

SOURCE: Sportcraft TX 2.5 treadmill - error code 3 - stops

Sorry I dont have the solution but I have the same problem.
Read somewhere that Sportcraft control boards had
a design flaw.

SOURCE: tredmill error code e1

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

John Mazmanian

• 832 Answers
• Posted on Mar 09, 2010

SOURCE: the treadmill starts then after a few seconds it

More likely LS= Loss Signal open the motor shroud on the motor their should be a cylindrical shape sensor (magnetic). Plug in treadmill and on the motor control board their should be a L E D (red or amber) by manually rotating the motor you should see that light flicker if it does sensor is good if not replace sensor. Next thing if sensor is good check motor brushes to see if they are mis-align or worn if worn less than 3/8" in length replace them