not sure how closely you looked at the traces, but its very clear to see what is malfunctioning in the trace. Comparing it against a normally running bike is of no additional value. Basically you'd just see normal ignition pulse timing across the entire trace instead of the occasional misses that show up in the trace on Jeff's bike.
Ignition Problem?
- Thread starter wjbertrand
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DavidR8
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Fair enough. Definitely don't claim to be even a rank amateur in this area.
I guess you check the +12V on the ignition coils with the scope.
Glitches might lead you in the direction of the tiltsensor or the stopswitch.
Glitches might lead you in the direction of the tiltsensor or the stopswitch.
ST_Jim
In the Hotel California...
Jeff,
I happened to be looking at the VSS on a clean schematic. The VSS module has 3 wires: +12V, ground, and a 0 to +5V pulse output. If there was an intermittent defect in the VSS module, or an intermittent ground wire, it could apply +12V to the ECM (and the speedo) on a pin that isn't supposed to see 12V. This could potentially cause the ECM to malfunction if it wasn't designed to tolerate this. Maybe this intermittent is excited by ~4000 RPM vibrations.
It's worth looking at. If not replacing it, maybe just pulling the connector or something and seeing if the malfunction stops.
I happened to be looking at the VSS on a clean schematic. The VSS module has 3 wires: +12V, ground, and a 0 to +5V pulse output. If there was an intermittent defect in the VSS module, or an intermittent ground wire, it could apply +12V to the ECM (and the speedo) on a pin that isn't supposed to see 12V. This could potentially cause the ECM to malfunction if it wasn't designed to tolerate this. Maybe this intermittent is excited by ~4000 RPM vibrations.
It's worth looking at. If not replacing it, maybe just pulling the connector or something and seeing if the malfunction stops.
OP
OP
wjbertrand
Ventura Highway
Yeah, met up with Bob at the show so I have the new sensor in hand. The hardest part is to access the connector, so I think since I'm in there I'll just do the swap. Such a rare problem, what are odds on two bad sensors??
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DavidR8
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Hi Jeff,
While looking for something else I ran across this post: Mystery Connection in Right Fairing
https://r.tapatalk.com/shareLink?share_fid=913&share_tid=156436&url=https://www.st-owners.com/forums/showthread.php?t=156436&share_type=t
The OP had to replace his VSS. My thoughts went to what issue required replacing the VSS.
Perhaps I'll ping the OP and ask.
Edit: I found his original issue: his speedometer stopped working.
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While looking for something else I ran across this post: Mystery Connection in Right Fairing
https://r.tapatalk.com/shareLink?share_fid=913&share_tid=156436&url=https://www.st-owners.com/forums/showthread.php?t=156436&share_type=t
The OP had to replace his VSS. My thoughts went to what issue required replacing the VSS.
Perhaps I'll ping the OP and ask.
Edit: I found his original issue: his speedometer stopped working.
Sent from my iPhone using Tapatalk
Last edited:
pretty sure its right behind the charcoal cannister
OP
OP
wjbertrand
Ventura Highway
Yeah, I had to access it when I installed the speedohealer, again when I replaced the main harness, and yet again when I removed the speedohealer. It's bit of a PITA.
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OP
OP
wjbertrand
Ventura Highway
I have heard of a few VSS replacements but I don't recall anyone describing symptoms like mine. Gave the sensor Bob loaned me a close inspection, the wiring and housing all look good. No 0-ring though, so I'll re-use the old one if it looks OK, if not I've got a bag of various sizes I can turn to. Looks like access the the sensor itself will be easier with bike on the side stand? Probably won't dive into this until Friday.
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Sorry about that, it's probably still stuck to the back of the engine!
4:
OP
OP
wjbertrand
Ventura Highway
No apology necessary Bob, you're doing me a huge favor! I need to look again in the baggie and see if it might have come off and is still in there but I don't think so.Sorry about that, it's probably still stuck to the back of the engine!
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I don't think it's there. I don't remember seeing one when I was cleaning it up!
OP
OP
wjbertrand
Ventura Highway
Well, I got energetic tonight and tackled the sensor change so it's done. I want to do the center stand in neutral test before I put the body Work back on, but not in the evening bothering the neighbors. Testing will have to wait until Thursday morning or Friday.
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DavidR8
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Oh the suspense!!!!!
ST_Jim
In the Hotel California...
Is it Friday yet?Is it Friday Yet?
cucumber1:
:strawb1:
:chat1:
What Igofar said!
OP
OP
wjbertrand
Ventura Highway
I was reading on a Honda car forum about how a failing VSS can produce symptoms similar to a bad coil or a bad TPS. I found this weirdly encouraging. Most of the time there are symptoms with the speedometer as well as error codes though too. Never had either of the latter. Wish I was off today to test it. I noticed the rubber block where the wires emerge from the sensor was cracked and dry-rotted on the old sensor, otherwise nothing obvious.
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