Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > Sport Touring: ST4 / ST3 / ST2 > Rev Limiter funnies

[John W]

Hello all,

just back from a cracking good time in frog-land on the ST4S.
Bike performed faultlessly with the exception of the above.

3rd day of the trip the bike suddenly dropped its limiter down to around 9k rpm. It remained like this for a couple of days, and then suddenly adopted it correct setting. Nothing else changed. I was using al different brands of petrol, so it wasn't a preticular brand. Oil etc were all as per normal.

One of the other ducati ST owners on the trip suggested it could be a faulty engine speed sensor.
What actually controls the limit - the ECU ?
(The bike has the DP performance ECU fitted).

Cheers all,
John.

[rockhopper]

Maybe the TPS breaking down?

I think the chip in ECU actually sets the rev limit.

[Monty]

Paul is correct, revlimiter is set by the ECU, but that monitors loads of other things so if it was getting a dodgy feedback from something it may reduce the revlimit.

John

[John W]

Thanks guys.

Does the ducati ECU log fault codes ? (i.e. is it OBD compliant).

I wonder if I take it to my dealer whether they'd be able to diagnose what is wrong, or would simply start swapping parts. Its running at the normal limit at present so it would be tricky to find by simple parts swaps.
It is due a service now so I'll mention it to them anyway, see what they say.

Btw, I know that on cars it is possible to interogate the ECU using some software such as VagCom for VAG range cars (OBDII since 96 I think).
I accept it might not diagnose the vehicle specific data but would this work for the Ducati ?
If so, anyone know what the connections are ?

Cheers,
John.

[rockhopper]

Nelly will tell you better than i can but i dont think it does log faults codes like car ones do. You can plug a Ducati tester into it which runs diagnostic tests on all the parts of the engine management system.

[Rushjob]

The ST4S ECU ( different to the 4 ) will give you fault codes so when the mechanic plugs his Mathesis or similar in he should be able to tell you the problem.
( Then he'll start swapping bits till it runs right )
Andy

[John W]

Cheers guys.

Andy, I see you have the same level of respect for the capabilities of the main dealer mechanics as I do
Assuming they set my mixture etc correctly after fitting the chip I guess they must have the correct mathesis tool.

Being a bit of a techie I'd quite like to know what you can & can't get out of the diagnostics socket. I also thought that all cars & bikes had to be OBDII compliant now.

Oh well, once I find out what they think the problem is I'll report back.

Cheers,
John.

[nelly]

All of the ECU's Ducati have used since the P8's store the error codes. Both historical and current problems are held in memory.
Some ECU's are able to offer more info than others, with the latest types offering up the most.
The mathesis tester can't, on it's own, set the mixture though. When setting the fuelling up it's used for setting the default TPS position, and on the 1.5M ecu's (SSie's) and 5.9M's (ST4S, S4, 749/999) for trimming the fuelling but after that you'll need a CO analyser piped into the exhaust headers to set the mixture.

[John W]

Thanks for clarifying things Nelly. I'll be sure to give the dealers a grilling to find out what is reported when I take it in.

Tell me, do you happen to know the spec of the diagnostics port.
Is it a standard RS485 port as used for OBDII on cars ?

I might try to get hold of the mathesis, but I'm wondering if the software I already have for the car will do it.

Cheers,
John.

[nelly]

The connection for the diagnostics is a three way AMP multipole connector tailed out of the ECU plug.
The mathesis connects into this.
The diagnostic software I have connects here to, via the 9 pin serial port on the PC.
Mathesis are very hard to get a hold of unless you are an authorised dealer. I got mine from one that had closed down a couple of years ago, and even then, the software cards I have only go to 2001.
I use the PC for most of the static stuff in the workshop and the new ECU's. The mathesis comes in handy for mobile work and setting the TPS etc.