Modern Vespa

Hi All.
About a month ago my MP3 500 went into what I would describe as limp home mode - it will not rev beyong 2/3k rpm. There are no dashboard warning leds on, the seat sensor looks fine, the tilt mechanism is ok and I have no issues with starting. It has been sat for a while with infrequent riding of late. I suspected fuel and battery so replaced both. I'm not sure if this model has a centre stand switch/sensor. I don't think its the immobilizer as there are no flash codes on the dashboard.

I've been through the forums looking for a step by step guide to diagnosing but so far I've not had any luck with identifying the problem. I have tried most of the suggestions.

The diag code returned from Guzzidiag is P0165 but not sure if this can be trusted. Details below:
Front throttle first self-learning NOT performed P0165 - test not carried out.
Error cause
• The first throttle self-learning process has not been successful or has not been carried out.
The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting.
• Delete errors hindering throttle self-learning.

ECU Producer: Marelli
Build:IAW 38RIU1
Ecu Prod: CM086902

Most of the data returned by the sensors through Guzzidiag look sensible but I have no way of validating the values.

Any guidance/advice you can offer in identifying what the problem may be would be greatly appreciated.

Last resort would be to get the scooter transported to the local piaggio garage but this will be costly and I would prefer to exhaust all DIY options first.

Thanks in advance

Reading through the description of the issue, it really sounds like the throttle limitation is active but does not display the symptoms. Checking the error codes shows a number of results related to Aprilia cycles about throttle.

Are you sure the throttle cable is intact and the throttle body is okay? Does it have a feeling of tension or torque when twisting the throttle like the cable is properly connected? You would have to dig into the plastic or get a endoscope camera to check the throttle body to make sure its all working.

Hopefully one of the more knowledgeable experts can chime in with some better guidance. You may be at a point that you need to just go to a shop.

Please let us know if you find out what the issue is so future folks can replicate the solution if they too encounter this problem.

have you cleaned the throttle body in particular the bypass channel?

Thanks for your replies.

Just to add one more piece of information which I thought was strange but might be useful - if the brakes are applied the RPM will go above 3k RPM and the throttle is responsive. This implies to me there is nothing physically wrong with the cable. As soon as the brakes are released the RPM falls back. This only occurs when the scooter is stationery.

I will have a closer look at the throttle body and cable. When I get a chance I will check all the sensors and connectors that feed the throttle body.

Surprised this has not been seen previously and there is no specific reference to the P0165 error!

applying brakes makes the engine go faster? WTF? That is spooky 👻

It doesn't go faster - but it *sounds* as though it does. This is because the rear brake locks the rear suspension and the main harmonic changes to a higher frequency. A very well-known effect on scooters with the engine as unsprung weight. There's hardly any change if just the front brake is used.

FAQ: Why does the engine sound different with the brakes on?

Maybe I need to clarify my last post!

The scooter won't rev above 2-3k RPM in its current state. Starts fine and idles fine, runs smooth with no spluttering or anything else.

However if you rev it up it immediately backs off at 2-3k RPM UNLESS you have the brakes engaged - then the RPM definitely goes above 3K rpm.

Thought this might be useful info as there may be some input/feedback to the RIU/ECU from the braking circuit which is overriding the failsafe mode which would help identify the root cause. Anyone want to offer up an explanation?

Havent made any progress with this yet. Its snowing in London at the moment so not ideal weather for working on the scooter outdoors!

OK.

Has this bike got ASR and/or ABS?

Hi Jim - yes its the ASR/ABS model for UK/europe.

I was hoping the revving above 2-3KRPM with the brakes on would eliminate any physical issues with the throttle body.

The scooter has been through some mucky UK winters and I was hoping it was just a dodgy connector somewhere in the RIU/ECU circuit.....

Never had any issues with it before and had it since new in 2016.

BTW - what's the easiest way to get access to the throttle body for cleaning?

Does it need all panels removed centre and sides for access?

I have had most of them off for one reason or another over the last 7 years.