Un-Broken!

Serves me right! I decided to give my GRiSO a service and now it's broken! All I did was fix the flat tyre and change the oils and filters. It started fine on the hoist but when I rolled it off and hit the button it blew the rearmost 15A fuse and lights up the 'ECU disconnected' icon. I haven't looked at the wiring diagram yet but Mark says the ECU has its own dedicated 3A fuse so it must be something that's interfering with the CAN signal, Grrrrr!

Fuckity, fuckity Fuck!

And Arse!  

Somebody will be offering advice.

Oh, I'll plough through it at my usual snail like pace but I'm hoping that one of the electrical boffins like Dave will have some bright ideas. I havent really touched it yet, Mark and Leah were here yesterday and I can't be arsed today. Tomorrow I'll push it back up on the bench and start pulling off the bodywork. The only thing I did after it started fine on the bench was put the wheel back on and have a poke around up by the front of the CARC reaction rod to make sure the bolt was tight. I'm thinking I that is the most likely culprit as there may of been a frayed wire and my poking has earthed it out against some bit of frame or pork-chop.

Pete

Any errors on Guzzidiag?

Nope. Nothin with OBD. I swapped out the ECU prior to checking the fuses, ('Cos I'm a dope and the ECU disconnected usually indicates a bricked ECU, I have several and it only took five minutes.). Then I saw the blown fuse and ran a diagnostic sweep with the OBD and got nothin' next is to plug in GD but I reckon it's just a short to earth. Gotta find what runs off that rearmost 15A fuse.

Pete

Right. After a nanna nap, I've had a good look at the wiring diagram. Bear with me, as my sleep-addled brain may still be dysfunctional. I suspect it's the 15A fuse that feeds the key-sense input to the ECU. This tells the ECU to 'wake up'. If this input isn't 'high' (+12V), the dash thinks the ECU is dead.

The key-sense is supplied from the main injection relay. It also powers the lambda probe heater, the secondary injector relay coil, the speed sensor & the startup relay coil. The startup relay activates the maintenance startup relay coil, which among other things, allows the lights to function.


Clear as mud? My brain hurts, so I could be relaying the gibbering ravings of my own self delusion.

First thing I would try is disconnecting the O2 sensor.

O2 sensor is long disconnected and exhaust plugged. It could be the connector shorting out. Gotta look.

Thing is the only thing I did after it ran fine was poke about up under the RH pork chop. I'm going to start there. I think it's something silly.

Well, that's where them relays hide. You may have disturbed the nest.

Confirming that everything looks normal with switch-on, it's only when the starter button is pushed, the 15A fuse (Fuse D) pops?

This fuse feds Lambda burner, secondary injection relay coil, start-up relay coil, speed sensor power supply, ECU power supply, engine kill button. Quite a lot to eliminate one by one.

Nah, it pops the moment power goes on. Speedo sensor is interesting as that may of got tugged when the brake came off.

Well, I'll be ripping into it this morning so hopefully by this arvo I'll of found the problem.

Thanks Dave.

Well, the suggestion that the speedo sensor was running off that fuse was the clue.

As is usual in these situations if something was working, then you worked on the machine and it became broken, the best thing to do is go back and look at the last thing you screwed up, I mean worked on!

In this case I'd had the wheel off to fix a flat. That requires removing the rear brake which means you pull the brake line and speedo sensor cable out of their clips and rest them on the bench. Usually this won't disturb anything but obviously it did.

Once I'd disconnected the speedo sensor the fuse stopped blowing when the ignition was turned on so I pulled off the sensor and found this....

[You must be registered and logged in to see this image.]

It had obviously got squeezed the wrong way in one of the clips on the frame and over time frayed through. My arseing about with the brake and brake line with the sensor attached was obviously the straw that broke the camel's back.

After punching myself repeatedly in the head for five minutes I installed a new sensor and 'Vroom'!

Thanks to Dave and Mark for pointing me in the right direction so I didn't have to spend the morning mouth breathing and pouring over the wiring schematic. I'd suspected the sensor but having my WAG verified certainly sped up the diagnosis.

Pete

Winner! Gotta love this forum - solutions abound.

Hey Pete, having had my arse end apart a 1000 times playing with plastic wheels etc, wondered how I hadn't stuffed up the speed sensor wire.

Had to check it. Mmmm, maybe coz I re-routed the wire up along the reaction rod with a few cable ties.
Never gets touched when I remove rear caliper etc.

Sometimes ya just get lucky.

Pete, I almost did that on my 09 back in the days...
Didn't severed anything but squished the wires pretty good with the washer bold from the caliper.
A freaking French working on an Italian machine...oh yeah, what a fukking combo!! lol