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Old 01-27-2013, 06:37 AM   #22
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Joined: Jun 2004
Location: Summerville, SC
Oddometer: 3,427
Originally Posted by thesurvivalist View Post
Why did pre 08 bikes require a tps reset?
The pre-08 bikes had a less-sophisticated ECM. They had a manually adjusted stop screw on the throttle body to set the idle speed. To set the TPS, you have to completely back off of this idle screw so that the butterfly is completely shut and the zero position of the TPS can be established and the TPS can be reset. You don't have to do this very often, but it's something of a PITA as you have to warm the engine completely, back off of the idle screw, connect a laptop with ECMspy or similar software to your bike, reset the TPS, then manually re-adjust the idle speed.

The 08-up bikes use an Idle Air Control (IAC) valve, which is automatically regulated by the ECM to maintain the idle speed. When you release the throttle, the butterfly completely closes; the IAV "bleeds" air past the butterfly to regulate the engine idle speed. This also means that every time you release the throttle, the butterfly is completely shut and the ECM can automatically reset the TPS.

Pretty cool, eh?
2007 Buell XB12X Ulysses
1983 Honda VT500FT Ascot
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