Error 22 indicates that the drive motor (running belt) has been instructed to start, by either
manual or program control, and the monitoring system has not received any response from the
speed sensing system indicating that the drive motor has started.
1. The treadmill utilizes an optical (infrared) speed sensor and the line of sight between the
speed sensor and the speed sensor target is obstructed.
2. Drive motor brushes are bad.
3. The speed sensor position relative to the speed sensor target is incorrect.
4. The speed sensor potentiometer adjustment is incorrect (when equipped).
5. The speed sensor is inoperative.
6. The lower PCA is bad.
7. The lower PCA to upper PCA interconnect cable is bad.
8. The upper PCA is bad
1. Carefully, vacuum out the drive motor compartment with a static safe vacuum cleaner. Pay
special attention to the area between the speed sensor and speed sensor target.
2. If the motor brushes do not make sufficient contact with the motor commutator, the drive
motor will not start when drive voltage is applied. Replace both drive motor brushes.
3. Adjust the speed sensor position so that the space between the speed sensor and the speed
sensor target is 3/16 inch and so that the speed sensor photo eye is aimed at the larger
portion of the targets wedge shaped section. On hall effect speed sensors (magnetic sensor)
the space between the end of the speed sensor and the flywheel tooth should be 3/16 inch.
4. Locate the speed sensor potentiometer on the lower PCA. Set the speed sensor
potentiometer at mid-range. Start the treadmill and increase the speed to 6 mile per hour.
Carefully adjust the speed sensor potentiometer to the point where the treadmill is operating
the smoothest. Increase the treadmills speed to full speed at repeat the previous adjustment.
These two adjustments are typically small and are usually only a matter of fine tuning.
5. If the speed sensor in inoperative the drive motor will start and run briefly before the error 21
occurs. If it is possible to access the speed sensor wiring, measure the D.C. voltage between
the speed sensor leads Two of the leads will constantly read approximately 5 Vdc. Two of the
leads will toggle between 0 Vdc. and 5 Vdc. as you slowly rotate the speed sensor target. If
you do not see both measurements above, the speed sensor is inoperative and must be
replaced. In some cases the speed sensor is mounted on the lower PCA and the the lower
PCA must be replaced.
6. Substitute a known good lower PCA to determine if the lower PCA is bad.
7. Substitute a known good interconnect cable for the existing cable.
8. Substitute a known good upper PCA to determine if the upper PCA is bad.