07 999S jump ground to ECU diagnostic and.... - Ducati.ms

Turboflyer · Jan 18th, 2012, 8:24 pm

Don't know exactly what happened not blaming the VDST certainly could have been me. But long story short, when I disconnected the VDST the bike began to run poorly and the FI module stopped working and a CEL. Oddly , when the diagnostic ground lead was connected to the battery every thing works and runs fine. So I am assuming a wire got toasted to or from the ECU. I made a jumper but sure would like to where the defective wire is. I don't suppose there is a negative fuse some where? At least it got me to clean all the contact points to include the engine ground. Thoughts?

pjonte · Jan 18th, 2012, 9:39 pm

Now that sucks

According to the wiring diagram the ECU has a single ground connection to it's case. You'll need to pull the battery and holder to get to it. Might get lucky and find its simply a loose connection, it seems to be problematic with 999's. Before you start ripping it apart get yourself a ohm meter and try to trace where the problem is. Put the ohm meter minus terminal on neg side of the battery wire. and the pos lead on the ECU housing. There are two screws showing on the exterior of the battery holder that hold the ECU in place, touch the pos lead on one of these. Anything more than a few ohms means that is the problem. According to the schematic the wire goes from the ECU directly to the battery thru the main harness. Not likely the VDST is the culprit. To clear that ground wire you would have to draw a ton of current, the other fuses would have blown or the VDST would have fried. My guess it simply a bad connection.

Turboflyer · Jan 18th, 2012, 11:18 pm

A little more research and possibly an ECU internal ground that is notoriously weak. The good side is I think I have at least found a work around. Do not know how it works but that ECU diagnostic ground pin is apparently patching through. Time will tell. Your right the main ground is a big wire so there should have been smoke. I did find some corrosion on the lug and cleaned both ends and every thing else I could see.

pjonte · Jan 19th, 2012, 6:22 pm

Personally, I'd highly recommend against using the VDST port signal ground as the main ECU ground. It has to carry all the current consumed by the ECU; spark plugs, injectors, relays and according to the schematic it also carries current directly from the fans. Basically any power consuming device or sensor that connects to the ECU passes its current through ECU ground connection. I'm sure the Ducati electrical engineers did not design the VDST connector, connector to the ECU or or the internal wiring within the ECU to carry that amount of current and will likely cause permanent damage. Also this ground serves as the ground reference for engine rpm pick-up sensor and the TPS potentiometer, voltage spikes resulting from high current will likely effect their accuracy to manage the engine. For the cost and effort of running a separate wire from the ECU case to the battery its just not worth the risk of frying the ECU or the connectors.

2C

Turboflyer · Jan 19th, 2012, 10:28 pm

No I understand the external ground, large current wire. The other (diagnostic) is an internal ground presumably for the ecu circuit board. I could be wrong of course. Seems to idle and run up fine. Will know tomorrow when I head out. I have a spare 999S ECU so whats the worst that could happen? Gets me thinking though and do appreciate the insight.
Could not wait took her out for gas tonight. Small wire intact and cool. Will go longer tomorrow.

ttpete · Jan 20th, 2012, 11:50 am

When using a VDST, connecting the battery clips backwards will fry the internal ECU ground. Once the clips are connected properly, the ground is re-established and the engine will run properly. Grounding the diagnostic port ground lead is about the only way to salvage the ECU. I suspect that when the battery connections are backward, it burns up a conductor track on a circuit board in the ECU.

Bella749 · Jan 20th, 2012, 4:51 pm

Quote:

Originally Posted by Turboflyer

A little more research and possibly an ECU internal ground that is notoriously weak. The good side is I think I have at least found a work around. Do not know how it works but that ECU diagnostic ground pin is apparently patching through. Time will tell. Your right the main ground is a big wire so there should have been smoke. I did find some corrosion on the lug and cleaned both ends and every thing else I could see.

This is exactly what I found with my bad OEM ECU. Traced the entire harness to find a bad internal ground within the ECU. I replaced it with a Microtec.

HI voltage charging condition
Diagnostics continued...