GTS300 doing weird things. ABS & ASR / EFI lights on and
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Vespa S150 ie & GTS300 SuperSport
Joined: 27 Apr 2014
Posts: 60
Location: SW Florida
Tue Jun 11, 2019 2:38 pm quote

We have a 2015 GTS300 with 1600 miles.

My wife was riding this morning and she claims it started shaking on her and the ABS & EFI / ASR lights came on. Also the speedo kept going from 0 to the speed she was doing. She also says the oil light came on. She may be confusing that though with something else? Anyway, the scooter then stalled and she said she couldn't start. So just called me. She claims she smelled burning.

So off i went to go pick her up. Tried the scooter and it started. No obvious oil loss, no obvious smells. Given it had started with me, i told her to just get it home for further diagnosis.

No its home i started checking all the obvious things, but i really can't see anything. I was honestly expecting perhaps a caliper had seized or something similar and it was freaking out the abs sensor. I checked that both wheels were rotating smoothly, which they both are. I checked the ABS / Speed sensor, it looks to be secured as expected.

The battery was only replaced earlier this yr with an OEM one. 400 miles ago.

For me, it doesn't seem to be having any mechanical issues. The scooter does seem to run smoothly. However the ABS light and EFI / ASR lights do come on and off. At random intervals. Perhaps 10secs on then off. When the lights are on, the speedo goes to zero, when off, the speedo resumes the correct speed.

I tried a couple of emergency stops, everything stops as normal.

However when slowing down, the scooter did stall on me a couple of times, but i had no issue restarting it. Nor did i see any oil light.

Any idea's of where i should start digging? Bad ABS sensor ? but that wouldn't have anything to do with the scooter stalling. I couldn't reproduce any shaking. So who knows. I don't think its mechanical. I'd almost say the ECU is going berserk. I know weak batteries cause all sorts of issues, but this battery is almost brand new. I've not tested it per se, but i doubt its the battery causing issues.

So appreciate any ideas.

Thanks in advance.
Vespa S150 ie & GTS300 SuperSport
Joined: 27 Apr 2014
Posts: 60
Location: SW Florida
Wed Jun 12, 2019 6:09 am quote
I should also mention that i checked the fuse for the abs module.. Along with all the other fuses while i was at it. All good.

Also when quizzing the wife, she said oil light may of been on, while it stalled. So as thought i don't think there's an issue there.
BV350, Primavera 150, Yamaha Zuma 125
Joined: 06 Jun 2013
Posts: 2619
Location: The Twin Cities of Minneapolis/Saint Paul, Minnesota
Wed Jun 12, 2019 7:05 am quote
This sounds like a loose connection to me. Check the battery terminals first; they're the easiest to get to. Then I'd check the ECU connector, kill switch, any cables to the dash in the headset, etc. Good luck!
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1867
Location: Not really sure but I think somewhere down South, in the engineering dept at Starfleet's UK HQ
Wed Jun 12, 2019 11:31 am quote
Concur with JKJ on this. It'll be something simple and may well be the battery terminal/s. It's not unheard of.
2009 LX 150, 2008 GTS 250
Joined: 19 Jun 2011
Posts: 673
Location: Birmingham, Alabama, USA
Wed Jun 12, 2019 1:56 pm quote
Check your tire pressures.

300 GTS, Stella 4T
Joined: 29 Jun 2018
Posts: 157
Location: EPX
Wed Jun 12, 2019 2:03 pm quote
Cosmos wrote:
Check your tire pressures.

I concur, when pressure is low my ASR goes all wacky.
Vespa S150 ie & GTS300 SuperSport
Joined: 27 Apr 2014
Posts: 60
Location: SW Florida
Thu Jun 13, 2019 6:12 am quote
Would ASR going all wacky cause the scooter to stall ?

I did check the tire pressures last weekend. I thought i made them exact according to the book (can't rememeber what they are as i'm at work) But that could be a co-incidence.. If anything the tire pressures will be high, unless there's a hidden nail somewhere, between last weekend and Mon when the missus took her out for a ride.

Pressures off, ASR kicks in, bike stalls to compensate wheels not rotating as expected.

Seen weirder things in my time, but hopefully it is something as simple as that.

But wow they do over complicate these little things if that is the case.

I was about to start pulling the damn thing apart. I'll double check the air first.
Vespa S150 ie & GTS300 SuperSport
Joined: 27 Apr 2014
Posts: 60
Location: SW Florida
Thu Jun 13, 2019 2:39 pm quote
lol can't believe i didn't check this first, but yep it was the positive battery terminal that was loose.

Spent x5 more time writing the original post than actually checking the terminals.

I thought that would be the last thing it would be given i'd cranked them down tight not all that long ago. Live and learn as they say. !! At least there's this out there for someone should they have the same weird issue crop up and next time i know straight where to go.

Thanks to all those who replied.

Problem solved !
2, aprillia scarabeo light. 500. 2007 2009
Joined: 29 Apr 2018
Posts: 642
Location: North central florida.
Fri Jun 14, 2019 2:15 am quote
Problem solved, good job everyone!
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