This document explains in detail how to use the ECM Software to reset the TPS on a Buell. It is not a comprehensive manual for ECMSpy, and it assumes that you have successfully installed the SW and are capable of communicating with the ECM.

 

Once you have the SW installed and working properly, go to the OVERVIEW screen and note that the TPS section in the bottom center has three different values: Degrees, %, and Volts.  Throttle voltage is an absolute reading. There is a Throttle Position Sensor potentiometer (pot) on the end of the throttle “butterfly” shaft, and the ECM is reading a voltage that varies depending upon the position of that pot. Depending upon how the shaft is attached to the pot, and the calibration of the pot itself, every throttle body will display a slightly different voltage when the butterfly is at any given position. This is why a TPS reset is mandatory any time the throttle body or Throttle Position Sensor is removed or changed. 

 

Throttle Degrees and Throttle (%) are positions relative to the zero point for the throttle butterfly. The purpose of a TPS reset is to tell the ECM what voltage is at the pot when the butterfly is completely closed (i.e., 0% open). The ECM is then capable of calculating the exact throttle position based on the offset voltage from the absolute voltage reading that it read when the butterfly was fully closed. Throttle degrees is the measure of the angle (degrees) that the throttle butterfly is open, and is a value between 0 and 85. Throttle % is the measure of the % open that the throttle is at, and is a value between 0 and 99%.

 

The first step of performing a TPS reset is to back the throttle stop screw off until it no longer is touching the stop on the butterfly shaft. The easiest way to check if the throttle stop is no longer engaged is to turn the throttle grip to zero and force it there gently. If when you start to open it, you can feel it gently sticking, this means that the butterfly is wedging in the throttle body and you have achieved absolute closure.

 

Run the ECMSpy SW, and put it in Overview mode. With the throttle screw backed off completely, force the throttle closed so that it gently sticks as described above. Re-open and do this a few times. BE GENTLE, you don’t want to overstress the throttle shaft by twisting it too hard against the stop. Note the Throttle (volt) value each time. It should be within .01 volts each time you do this. If not, there is something wrong with the throttle body or Throttle Position Sensor.

 

Click on the Diagnostics tab. You will see a button that performs the TPS reset function. Clicking that button will reset the ECM so that it thinks that the position that the throttle shaft is current at is the zero degrees/zero percentage (but NOT zero voltage) position.

Before you actually reset your TPS to zero, I recommend that you perform a test of the TPS reset procedure in order to confirm that the TPS reset is working properly. This is optional but may save some headaches if things don’t seem to be working right later. Hold the throttle in the 1/3 open position, and then execute a TPS reset in the Diagnostics mode with it held steady there. The throttle should be held steady while the TPS is performed. Go back to Overview mode, and slowly open the throttle. If the Throttle degrees and percentage remain stationary until you cross the threshold position that you held the throttle at (i.e., 1/3 throttle) and only then starts climbing, THEN you know that TPS worked correctly and that you have successfully set the TPS (at the WRONG 1/3 open position).

 

If that worked correctly, shut the throttle and gently force it closed at the throttle grip. Execute the TPS reset. Go back to Overview display mode. Slowly turn the throttle stop screw up until you get a Throttle Degrees Reading of 5.5 or so. The exact number doesn’t matter, you’re just getting it so that the engine will start and idle. Start the engine, let it warm up until an indicated temperature of 320F, and adjust the idle to 1050 and you're done.