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Old 08-26-2012, 01:56 PM   #5235
Biped
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Joined: Jul 2008
Location: Oregon, Wet Side
Oddometer: 287
TPS Gremlins

My TPS gremlins continue....
Not sure if anyone else has had this issue or could point me in a direction for further diagnostics.
Issue: While riding, any gear, any speed, or bike stationary at idle, I randomly get an FI solid on light and the engine tone changes. Going to Neutral provides a 9 x long flash indicating a TPS issue.
Well, I first check all TPS related voltages via TuneECU and all were within spec. I checked all wiring for chaffing, short to frame etc and nothing. I then replaced the TPS with a new one and reset the voltages. Unfortunately same error/issue persists.
I decided to check the TPS voltages directly to see if I could find an abnormality. I used pins to back probe the TPS connector to a logging DVM. What I found was interesting. The working voltage was a steady 4.98V which is great. The sense line voltage was at 0.58V while idling normally, which is what should be expected. When the FI issue occurs the sense voltage jumps to 0.71V and stays there. The working voltage does not change. If I cycle the key or kill switch all goes back to normal.
From what I can gather is that somehow the stepper motor must be getting a signal to move the butterfly a set amount, independant of throttle position, at random times which seems the only way the sense voltage on the TPS would change a set amount and stay static.(some randon butterfly to throttle position offset) The wiring diagram does not have any info on the 8 position stepper plug pin-out for me to analyze. Are there any sensors that control this stepper (left side throttle body) or is it driven through the ECU only. I would prefer not to buy a new throttle body to see if the issue goes away or not.

Any thoughts....this just started happening about 250 miles ago. Have not done any mods/mapping for about 8k miles. Running a version of the Beaney map FWIW.
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