Modern Vespa

Took my MP3 500 on a long run up to London and back at the weekend with no problems at all.

Took it to the supermarket a mile down the road yesterday and on the way back the engine management light came on.

It did the same thing today on the 15 mile ride to work.

The strange thing is if you switch off the engine and restart the light goes out and there are no obvious performance issues with the bike itself.

I can see that other owners have had the same problem due to a faulty voltage regulator. Can anyone think of any other possible causes?

I can take it to my local Piaggio dealer but your looking at a 60 mile trip which I don't want to be doing if it will damage the bike further.

Also does anyone know of any home diagnostic kits that may be available?

Speaking from being a MP3/250 Owner...
I had this problem before, and this is what cured it.
The bike ran OK, I just had that light that stayed illuminated all the time.

1. Changed Spark Plug.
2. Replaced O2 Sensor.

The Dealer can plug in a Diagnostic Pad, and it will tell them the problem. But if it is multiple problems, it throws this device off.
Following the Dealer advice you would change one, and then the light would come on again, and you would have to change the other.
This is what happened to me.

Good Luck,
Keith
Marietta, GA

Looks as though checking the voltage regulator is the easiest place to start.

Just need to check the charge with a multimeter when the engine is idling and at higher revs.

If this is OK I'll try and book it in for a diagnostic.

Since you live in a mostly damp environment coupled with salty air, that might be what is causing your issue. It might be a corroded connection.

On long trips in a dry environment some times my 400 MP3 light comes on intermittently in high altitudes @ 65 mph. The 1st time I pulled over to make sure there was plenty of oil in the motor and nothing else visible to cause a warning light. Saw no issues and motored on. Still intermittently the light would come on. I ignored it and hundreds of miles later nothing bad happened. My MP3 only has about 15K miles on it. I do all it's maintenance myself. If it happens again I'm just going to ignore it again until the thing quits running.

This could be a problem with the lambda sensor. If it does not give consistent reading after some time the ECU decides it is faulty. It then puts the engine management light on and ignores the lambda sensor until the ignition is cycled on/off/on.

The lambda sensor can be tested to some extent. It has 4 wires. Two of these feed an internal heater element ( because the sensor needs a certain minimum temperature to work). The other two send a signal to the ECU which cycles between 0 volts and 1 volt as the oxygen level passes a certain threshold.

I can't tell you the wire colours but the heater has a permanent battery feed when the fuel pump is running ( ie when the engine is running) and the other wire goes to pin 21 of the main ecu connector.

OK I have come up with some possible wire colours but don't take this as gospel:-

sensor wires light blue/black and white/green
heater wires green/yellow and black/green

The sensor wires go to pins 4 and 11 and when the engine is running at normal temperature you should see the value cycling between 0 and 1 volts as you open and close the throttle. ( You need a reasonably good quality digital voltmeter).

Sensor problems can just be caused by oil or carbon deposits. If the engine is run at high speed for a while they are usually self cleaning but if this is not your style of riding the sensor may have sooted up.

Hope this helps.

Regards Roadster

As the trike is still under warranty I have booked it in with my local dealer for a diagnostic. The diagnostic is free.

Once they have located the fault they will check to see if it is covered under the warranty or if I will have to pay for the repair.

My local dealer is 30 miles away. When I spoke to them they initially told me that Piaggio have advised them that for warranty issues the trike needs to be returned to the dealer from which it wa bought.

The problem here is that they are 150 miles away.

> they initially told me that Piaggio have advised them that for warranty
> issues the trike needs to be returned to the dealer from which it was
> bought

Nonsense.

Total crap. They probably just didn't want to bother to do it themselves.

Before Piaggio pays for anything under warranty you have to take your MP3 to a dealer and they have to submit the problem to Piaggio., then wait for the OK from P to have it covered under warranty. Till then your MP3 sits.

I agree with Jimc, to be a Piaggio/Vespa Dealer I thought they are Required to take in the Repair !

Tested the voltage at the battery today.

12.5V at idle rising to 14.5v when throttle applied so not a regulator problem.

Will change out the spark plug tomorrow as it probably needs changing anyway as its done 6000 miles.

If that doesn't work we'll see what the diagnostic reveals.

Don't really want to have to leave the trike with dealer while Piaggio makes a decision over the warranty.

If your engine is delivering its full power output and is not misfiring then I don't think there can be a lot wrong with the spark plug. The engine management light only responds to electronic faults from its sensors so I think the lambda sensor is still odds on favourite.

Took my MP3 to my local dealer.

Their process is:-

- Hook up to the computer to perform updates (approx 2 hours).
- Run the diagnostic to isolate fault.
- E-mail Piaggio to get approval for repair under warranty. Wait 48 hours for a reply.
- Order parts.
- Fit parts.
- Check to make sure fault is resolved.
- I can then collect the bike.

This could mean leaving the bike with them for a week.

Rather than do this I will source a replacement LAMBDA sensor at the weekend and fit this to see if it sorts things out.

These can be a tight fit and need a decent spanner ( 22mm I think). It is also easier to remove them when hot. Don't be tempted to use lubricants anywhere near the sensor. These contaminate it and you'll end up with two problems rather than one. If you want to put something on the threads of the new one ( copper slip for example ) do so very sparingly.

Regards Roadster

Finally got round to fitting a new LAMBDA sensor.

Didn't fancy paying for the official sensor as the cheapest price I could find was £45.

Instead I bought a universal 2 wire sensor off e-bay and recycled the original connector.

So far no problems. The engine management light comes on briefly when I put the key in the ignition and then goes off and is staying off when riding.

All I need to do know is book a service.