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2005 gsxr 750
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25 Posts
Discussion Starter · #1 ·
Hey guys what's up David here with a quick question that I know has been covered immensely on this platform. Just cant find the right thread to help me out so I figured I'd put my own up. My bike runs great and everything is working properly. But when I first start my bike my secondary butterflies stutter and I get c28 code witch I know that's for the stva. But then I turn the bike off and quickly back on and code is gone and butterflies dont stutter. Can anyone help me out with this.
 

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I was trying to avoid going to the dealer they ate crazy expensive. But I might just have to do that. Thanks for the advice.
I normally do all the wrenching on my bike but I just wanted to drive and I work crazy hours only had one day off and I was like no damn way I’m spending it working on my bike they had my bike for two days and it cost me like 300 bucks


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· Dreaming of buttsecks for years...
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15,101 Posts
What you're describing sounds more like a faulty secondary throttle position sensor. The way the SDTV system works is that the ECM tells the STVA to move, and then the sensor reports back a position. This is done basically by voltage. As it closes the voltage is low, and as it opens, the voltage rises. In some cases, the resistor system in the sensor gets shorted turning the wiper into a dual resistor system. When the sensor reaches/passes this point, the ECM interprets the signal as incorrect and thinks the STVA is moving erratically. Although C29 is the code for the sensor, the ECM is still seeing the sensor and the voltage from it. Because your problem happens at prestart and the secondaries sweep their entire range and then set that value in the ECM, it sees that hiccup. But, if you turn off and on, the secondaries are already open and it doesn't experience the bad spot in the sensor.

An easy and free way to prove this out is swap the primary and secondary throttle position sensors. On the 2004-2005, the sensors are the same part (just make sure not to confuse the connectors, primary is grey, secondary is black). Make sure you follow the procedures for installation. If you don't install them correctly, you can damage them. If your problem is resolved, buy a new sensor and replace the now primary sensor.
 

· Premium Member
2005 gsxr 750
Joined
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25 Posts
Discussion Starter · #10 ·
What you're describing sounds more like a faulty secondary throttle position sensor. The way the SDTV system works is that the ECM tells the STVA to move, and then the sensor reports back a position. This is done basically by voltage. As it closes the voltage is low, and as it opens, the voltage rises. In some cases, the resistor system in the sensor gets shorted turning the wiper into a dual resistor system. When the sensor reaches/passes this point, the ECM interprets the signal as incorrect and thinks the STVA is moving erratically. Although C29 is the code for the sensor, the ECM is still seeing the sensor and the voltage from it. Because your problem happens at prestart and the secondaries sweep their entire range and then set that value in the ECM, it sees that hiccup. But, if you turn off and on, the secondaries are already open and it doesn't experience the bad spot in the sensor.

An easy and free way to prove this out is swap the primary and secondary throttle position sensors. On the 2004-2005, the sensors are the same part (just make sure not to confuse the connectors, primary is grey, secondary is black). Make sure you follow the procedures for installation. If you don't install them correctly, you can damage them. If your problem is resolved, buy a new sensor and replace the now primary sensor.
So I replaced the sensor and installed it according to the manual and it's still doing the same thing.
 

· Premium Member
2005 gsxr 750
Joined
·
25 Posts
Discussion Starter · #11 ·
What you're describing sounds more like a faulty secondary throttle position sensor. The way the SDTV system works is that the ECM tells the STVA to move, and then the sensor reports back a position. This is done basically by voltage. As it closes the voltage is low, and as it opens, the voltage rises. In some cases, the resistor system in the sensor gets shorted turning the wiper into a dual resistor system. When the sensor reaches/passes this point, the ECM interprets the signal as incorrect and thinks the STVA is moving erratically. Although C29 is the code for the sensor, the ECM is still seeing the sensor and the voltage from it. Because your problem happens at prestart and the secondaries sweep their entire range and then set that value in the ECM, it sees that hiccup. But, if you turn off and on, the secondaries are already open and it doesn't experience the bad spot in the sensor.

An easy and free way to prove this out is swap the primary and secondary throttle position sensors. On the 2004-2005, the sensors are the same part (just make sure not to confuse the connectors, primary is grey, secondary is black). Make sure you follow the procedures for installation. If you don't install them correctly, you can damage them. If your problem is resolved, buy a new sensor and replace the now primary sensor.
I don't know if I'm installing it wrong in the manual all it really tells me is how to adjust it to the right resistance
 

· Premium Member
2005 gsxr 750
Joined
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25 Posts
Discussion Starter · #17 ·
Ok I'll try setting it there when I get home today from work. I can try to up load something today when I get home aswell.
So I removed the stva from the bike an left connector on it and turn my key and boom I noticed the stuttering noise the I thought where from the butterflies is actual from the stva. The piece where the secondary butterfly shaft goes through is cause the issue
 

· Dreaming of buttsecks for years...
Joined
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15,101 Posts
^^^^ NEVER NEVER NEVER power up the STVA when it's not on the throttle body. The secondary throttle shaft is a integral part and when it's removed from the throttle body it's partially disassembled. This can jam it up and cause irreparable damage!!!
 
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