Speed goes fast than slow than fast- error code 22

Precor Error Code 22 Error Code: 22 Manufacturer: Precor
Model: All Models
Error Description: Error 22, No Motor Pulses at Start Up - Error indicates that the display has sent a command for the drive motor to start, however, the speed sensor has not returned the signal acknowledging that the drive motor has started. Possible Reason:

1. The line of sight between the speed sensor and the speed sensor target is obstructed.
2. Badly worn drive motor brushes.
3. Incorrect gap between the speed sensor and the speed sensor target.
4. Incorrect adjustment of the speed sensor potentiometer (when equipped).
5. Inoperative speed sensor.
6. Faulty lower PCA.
7. Faulty interconnect cable between upper and lower PCA.
8. Faulty upper PCA.

1. Using a static safe vacuum cleaner, carefully vacuum out the drive motor compartment. Be sure to thoroughly clean the area between the speed sensor and the speed sensor target.
2. Bady worn drive motor brushes cannot make proper contact with the motor commutator, therefore the drive motor will not start when voltage is applied. Inspect and replace drive motor brushes if necessary.
3. Inspect the gap of the speed sensor to the speed sensor target. Proper gap is 3/16" and the speed sensor photo eye should be aimed at the larger portion of the targets wedge shaped section. If unit has a magnetic speed sensor, the gap between the end of the sensor and the flywheel tooth needs to be 3/16".
4. Locate the speed sensor potentiometer (when equipped) on the lower PCA. Set the speed sensor potentiometer to mid-range. Start the treadmill and increase speed to 6 mph. Carefully adjust the speed sensor potentiometer until the treadmill is operating the smoothest. Increase the speed to full speed and again adjust the speed sensor potentiometer until the treadmill is operating the smoothest. These two adjustments are typically small and are generally only a matter of fine tuning.
5. An inoperative speed sensor will allow the drive motor to start and run briefly before the error appears. If able to access the speed sensor wiring, measure the DC voltage between the speed sensor leads. Two of the leads will always read about 5 VDC. Two will toggle between 0 and 5 VDC as you slowly turn the speed sensor target. If both measurements are not seen, the speed sensor needs replaced. Some units have the speed sensor mounted on the lower PCA and the lower PCA needs replaced.
6. Determine if the lower PCA is bad by swapping with a known good lower PCA.
7. Determine if the interconnect cable is bad by swapping with a know good cable.
8. Determine if the upper PCA is bad by swapping with a know good upper PCA.