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@randyjaco avatar
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2019 GTS 300
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Hello all,
I am the new owner of a 2019 GTS 300 with @30K miles
Today while riding, the orange engine management light came on
Doing a search on this website, I see that it is a common problem.
So, how does one do diagnostics to find out the problem? What equipment do I need, and Where do I need to go to get more info?

TYI
Randy
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Hooked
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I think the diag port is proprietary Piaggio/Vespa and only dealers have access to the scanner hardware/software. I suppose there may be units in private hands. Perhaps someone on here can hook you up.

2024 models come with OBDII due to more recent European laws. Maybe a year or two earlier as well, but I don't think the 2019s have it.
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If, tomorrow, it doesn't come on right away when you start, but only after you've revved it a bit, then suspect the regulator. You'll need a cheapo multimeter to diagnose this (assuming you're in the US, get a $10 harbor Freight one), and check the voltage at the battery with the engine revving when the CEL has come on. If over 15V, then you have a bad regulator. This is the easiest test you can do before further head-scratching and probably a dealer visit.
@steelbytes avatar
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2019 GTS300 HPE SuperTech 67,000km
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Depending on when and where, a 2019 300 is an HPE and has standard ODB2 eg my 2019 does. Pre HPE doesn't have ODB2.

pre HPE
DIY Diagnostic tool for injection Vespa's with MIU ECU
(or dealer)

HPE
GUIDE: How to read Engine Fault Codes (OBD/OBD2)
(ie use any standard odb2 tool)
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2019 GTS 300
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Thanks for the replies
The scooter is very new to me, I have put on less than 100 miles on it, and it has been running perfectly. I have owned multiple motorcycles and scooters, and earlier on in life was a motorcycle mechanic. I do all my own maintenance. I have a OBC2 reader and a GS911. The nearest Vespa dealer is over 100 miles away. On purchasing the bike, I did a complete check-out. Every thing looked good. It was in remarkable shape. The previous owners took very good care and maintenance on it. The previous owner said that he had replaced the water pump.

This morning I checked the scooter. The battery when I turned on the ignition was 12.4 volts. I cranked the bike and it was idling rough. In fact, it stopped running twice on warm up. At idle, the voltage was at 13.7v. But I couldn't rev the motor. I drove the bike around the block to warm it up. When I drove it back into the driveway, it died
I started it up again and revved the engine. The max voltage was 14.2 volts; so I think that eliminates the voltage regulator.
I know the tank has regular gas in it, so I will drain it and put in premium.

If the bike has a OBC2 or any other diagnostic port, where would it be located?

Thanks again guys Clap emoticon
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Well, I filled her up with premium gas and turned up the idle a bit. The engine is running very smooth and runs like it should, but I still have that blasted yellow light
Is there some way to cancel it and see if it reappears?
Not sure what to do next?
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Here are some pics to show you what I am working on. Not bad for a 5 year old bike with 30K miles
Forum member supplied image with no explanatory text
Forum member supplied image with no explanatory text
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Hooked
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SteelBytes wrote:
Depending on when and where, a 2019 300 is an HPE and has standard ODB2 eg my 2019 does. Pre HPE doesn't have ODB2.

pre HPE
DIY Diagnostic tool for injection Vespa's with MIU ECU
(or dealer)

HPE
GUIDE: How to read Engine Fault Codes (OBD/OBD2)
(ie use any standard odb2 tool)
In the US the first year for the HPE is 2020.
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Well, It self-corrected.
I am guessing it was the premium gas. I took it for @ a 20-mile ride. During the ride, I looked down and no yellow light Clap emoticon
I am still curious about the diagnostics. I am guessing that it is not the last time that I will see that sucker
But for the moment it's running great

Thanks
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Randyjaco wrote:
Well, It self-corrected.
I am guessing it was the premium gas. I took it for @ a 20-mile ride. During the ride, I looked down and no yellow light Clap emoticon
I am still curious about the diagnostics. I am guessing that it is not the last time that I will see that sucker
But for the moment it's running great

Thanks
Hey mate,

what is the oil level like? change the oil filter, oil and air filter, add some fuel injector cleaner and go for a good ride these scooter are bullet proof.

cheers

Simon
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The maintenance was done @ a month ago. Everything is clean or new. It's an extremely clean and well maintained scooter
@steelbytes avatar
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2019 GTS300 HPE SuperTech 67,000km
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apex wrote:
In the US the first year for the HPE is 2020.
I know, but the OP didn't say where they are (or I missed it). Europe got it end of 2018. Although I probably should guess the US since they said miles not kms, but could be the UK
⚠️ Last edited by SteelBytes on UTC; edited 2 times
@steelbytes avatar
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Randyjaco wrote:
If the bike has a OBC2 or any other diagnostic port, where would it be located?
for hpe with odb2 look for a red plug with a cap on the left of the engine bay. for pre-hpe with non-odb2 look for a black plug with a cap on the right. check the two guides to understand the type of plugs.
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So, is this the Vespa diagnostic plug and if so, does it have a name?
Forum member supplied image with no explanatory text
@steelbytes avatar
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Randyjaco wrote:
So, is this the Vespa diagnostic plug and if so, does it have a name?
yes, that is the pre-HPE plug. The article I linked above calls it a Fiat cable
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Thanks for the info. I am afraid that connection stuff is way above my tech capabilities. I just need the ability to read the error codes, not remap my fuel injection.
@steelbytes avatar
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2019 GTS300 HPE SuperTech 67,000km
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well maybe put the thought of reading the codes to the side and focus on what you can do. eg the battery should read 14.2 when idling and 14.5 when reving.
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Randyjaco wrote:
and turned up the idle a bit.
I don't think that's possible on these bikes
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2019 GTS 300
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It is pretty easy. Just remove the paint and insert a 3mm (?) hex key in the throttle stop adjustment screw
It can also be done by adjusting the throttle cables.
@steelbytes avatar
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2019 GTS300 HPE SuperTech 67,000km
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And cause an engine light 🤦‍♂️
@jimc avatar
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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UTC quote
Randyjaco wrote:
It is pretty easy. Just remove the paint and insert a 3mm (?) hex key in the throttle stop adjustment screw
It can also be done by adjusting the throttle cables.
ARGH! That is something you should never do - it's a one-time adjustment made at the factory to set the tiny gap in the butterfly before the TPS (throttle position sensor) setting is programmed into the ECU.

Adjusting the throttle cables so tight that there is no free play at 'zero throttle' is also a BAD thing - newer models won't even start if you do that.

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