I bought a secondhand 1.2 8v grande punto (2008) during November 2014. Last January a series of problems came up as follows :
I noticed moisture in the rear lights and inside the luggage space. A few days later left turn signal went out giving me a blinking warning sound. It turned out that rain water entered both the rear lights and all bulb connections had been corroded. Further more the hose that supplies water to the rear window had also been torn and more water entered the rear side of the car. I had it fixed which means that they replaced the hose, cleaned faulty bulb connections, replaced all the bulbs and i must say that my car as ok for one week when suddenly:
While i was driving I lost power steering (esp warning light came on), abs warning light came on, handbrake light came on, speedometer and rev meter dropped dead to 0. That lasted for 15 or 20 seconds and everything went back to normal except the abs light that was still on. I pulled aside, switched off the car and then back on and everything was good including the abs warning light. Ever since the same pattern repeats 5-6 times a day and lasts for no more than a minute. At the end the abs light stays on until i switch off the engine and turn it back on. Sometimes it gives a break of normal functioning for one week or 10 days but then the problem returns.
Please note that sometimes when I try to switch on the engine after the problem has appeared the key lock warning light also comes on and the engine won't start until i press the clutch pedal!!!! Diagnostic tool gives a can bus error. We have replaced battery, clean the grounding points on the chassis ( I believe there are 3 of them) but no problem solved. Any ideas?

Can bus error means the can bus isn't reading everything. Try a can alignment via mutliecuscan or main dealer to see if that fixes the error

yes I think it is time to visit the central Fiat dealer in my area. Thank you for reading my problem. Can alignment is a software thing?

This sounds similar to what's happening with my car, when I start the car and pull away the power Stops but kicks in and stops again repeatedly for about 10 seconds, and like you my esp turns off, also hill holder but I could turn the car off and back on and it will all be fine!

Yes a can alignment is where the can bus resets itself to see any modules and aligns them properly. This needs doing when modules get changed.

Before go fiat just make sure that all the earth's under the bonnet are fine. Go to the guides section to find a guide stating where they all are. A bad earth can cause the car to play funny in way of stuttering etc

I have an appointment with my local Fiat dealer next Thursday. Meantime I think I may have found a pattern. It seems that most of the times the problem appears when I want to stop (for example when I have in sight a red traffic light), I let go of the acceleration pedal and then press the clutch pedal and the brakes. Seconds after I press the clutch pedal problem appears! I have to continue driving for a few meters and the warning lights go off except of course the abs light which stays on. I am wondering could this be happening due to lost information from the abs? That wouldn't explain loss of eps (since eps needs the information of the wheel rotation) and loss of speedometer?

Abs only kicks in when your tyres are locked (unlikely kick in during normal stopping less slamming on). Sounds like a faulty abs sensor and maybe can bus not reading properly. The dealer should be able to tell you more when they do a diagnostic test

After 1 week of searching in an authorized fiat dealer and a few re-soldered grounds it looks like the problem came from a bunch of cables. These cables are connected to BCM ( one end ) and the other end is to the left of the clutch near left drivers foot. Unfortunately they did not explain to me if they were broken or had a loose end. I have to drive for a couple of weeks until I make sure that was the problem