What would cause a TPS to change on its own?

AxelW
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AxelW
Bike is a 2020 FC350.
Bike wouldn’t start and if you got it running it had no idle and ran very poorly. Checked the TPS voltage and it was around 2 volts at closed throttle. From what I have found on the internet it should be around .5 so I sat it to that and bike fired up like normal.
Is the TPS going bad? It was not loose so I don’t think that it had moved on its own.
Thanks in advance.
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Richy
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Richy 10/6/2021 2:28pm
10/6/2021 2:28pm
Usually they're supplied a 5v 'reference' voltage from the ECU, and return a signal of 0 - 5v to the ECU depending on throttle opening.

Orientation and how they work can vary, i.e. you mention this particular sensor should read 5v with the throttle closed, and it doesn't.

If that's the case and you're only seeing 2v, then assuming you don't have a loose connection (you mentioned you don't), you don't have a bad or loose ground (worth checking grounds, that they are clean and tight, ground issues can cause weirddd shit), and there is no damaged wiring (bearing in mind even a fairly severely damaged or pinched wire can show continuity well on a DMM), then the simplest answer is probably going to be THE answer...

The sensor is probably duff.

One last quick one, worth checking battery voltage, if it's low it too can cause some weird shit, however if it cranks and can drive the fuel pump it should have more than enough juice to power a few hundred milliamp TPS.
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AxelW
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AxelW 10/6/2021 3:51pm
10/6/2021 3:51pm
Richy wrote:
Usually they're supplied a 5v 'reference' voltage from the ECU, and return a signal of 0 - 5v to the ECU depending on throttle opening. Orientation...
Usually they're supplied a 5v 'reference' voltage from the ECU, and return a signal of 0 - 5v to the ECU depending on throttle opening.

Orientation and how they work can vary, i.e. you mention this particular sensor should read 5v with the throttle closed, and it doesn't.

If that's the case and you're only seeing 2v, then assuming you don't have a loose connection (you mentioned you don't), you don't have a bad or loose ground (worth checking grounds, that they are clean and tight, ground issues can cause weirddd shit), and there is no damaged wiring (bearing in mind even a fairly severely damaged or pinched wire can show continuity well on a DMM), then the simplest answer is probably going to be THE answer...

The sensor is probably duff.

One last quick one, worth checking battery voltage, if it's low it too can cause some weird shit, however if it cranks and can drive the fuel pump it should have more than enough juice to power a few hundred milliamp TPS.
I did have a similar problem earlier this year where the bike wouldn’t start. That time I switched out the ground going from the battery and that fixed it. Unfortunately I did not check the TPS that time so I don’t know if there’s a correlation.
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willbilly
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willbilly 10/6/2021 5:23pm
10/6/2021 5:23pm
TPS moved when tightened after adjustment or idle speed was changed are other possibilities.
AxelW
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AxelW 10/7/2021 1:28am
10/7/2021 1:28am
willbilly wrote:
TPS moved when tightened after adjustment or idle speed was changed are other possibilities.
I haven’t loosened the TPS before it happened or changed the idle

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Paw Paw 271
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Paw Paw 271 10/7/2021 2:47am
10/7/2021 2:47am
THESE DO WEAR. You can check them on the bike from time to time and adjust as needed. These units were never designed for the rough and tumble life of a dirt bike and should be considered to be a wear item to replace from time to time.

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AxelW
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AxelW 10/7/2021 3:48am
10/7/2021 3:48am
Paw Paw 271 wrote:
THESE DO WEAR. You can check them on the bike from time to time and adjust as needed. These units were never designed for the rough...
THESE DO WEAR. You can check them on the bike from time to time and adjust as needed. These units were never designed for the rough and tumble life of a dirt bike and should be considered to be a wear item to replace from time to time.

Paw Paw
Thanks. I think I’ll change it just for peace of mind.
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willbilly
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willbilly 10/7/2021 5:10pm
10/7/2021 5:10pm
On a two year old bike I wouldn’t think that it would be worn out. They are susceptible to crash damage. They’re expensive so I would get the aluminum guard for it.

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