355 problem.

I forgot to add that, once I had fitted the two new ecu's, it took a good 10 or even 15 minutes before the slow down light went out (following the usual switch off, switch on battery for a reboot with a cold engine and all ancillaries off). I suppose that in your case you will be in no doubt - hopefully when 4 cylinders become 5. Maybe you will be fitting them this evening?

 

Hells bells! had delay on 2nd unit arriving but got it now, so will try it out in morning. and will leave running for a bit!

 

Of course I meant when four cylinders become eight! Come on, get out of bed and fit that second ecu and let us know if it's champagne or cold tea!
All the best.

 

5,6,7 anything would be better than the 4 i am still getting. At friends garage now and we are swapping over stuff with his 355 tomorrow morning. we think it is problem between the cat ecu and car ie wiring or main ecu. so going to start with that and on from there! update tomorrow! mind you nice new green top cat control units look very smart, just dont put that light out.

 

That's a pity - but they needed replacing anyway. Good that you have found a source for swapping. Good luck and you can see how many people are following your story.

 

Didn’t have as much time as I thought today as on 3 line whip from home re visitors and going on a picnic in sun. But did manage to work on car this morning, started by putting on the cats kindly supplied by Monteman (we have to have cats now for competitive use). I thought that i should change then as in same area of the problem and will need to do it anyway.

They aren’t as easy to get to as you would think - or wish are they! Took a couple of hours to swap over, what with freeing up rusted bolts etc. I was rather excited to find one of the wires on a lambda sensor was loose, nay when pulled came away from its connection and thought hurrah that’s the problem. I could go to picnic in the Ferrari.

Replaced with a spare we had, finished it off and all connected up and fired up – no change! Did a hard reset and cut battery. No difference. No time for anything else.
More soon as we move on to other possibilities.

 

You must be getting a bit frustrated by now! As you know the European models do not have the connector block under the dash that the USA supplied cars are blessed with and it's therefore not so easy to read (and clear) the error codes in the main ECU. Maybe stored error codes could still give you problems (even if all else is healthy)? Failing a trip to a Ferrari dealer who can look at these codes it's maybe time to look at the values coming out of the cat ecu's...............

 

Certainly one train of thought that could be happening for sure. Im hoping when we swap ecus that may show us if this is a possibility. ive also just bought an ecu unit on fleabay whilst it was there just in case! I could get it to a ferrari independent but nearest is 25 miles away then 50, so would want to get it towed over. they are keen to do whole thing and leaving ti with them rather than just put an sd3 on it for readout. Im less keen on that! could go to other one who are more helpful in doing what i want. but havent exhausted all avenues here yet. hope to get over again tomorrow night for more fun and next stage of the happy saga.

there are 2 fuses to the cats i think and are there 2 relays? just a thought i need to look at them if so???

still need to get the thing ready for competition which is where Im loosing time.

 

The CAT ecu's only need the +12v supply, an earth and the signal from the T/C to process and send the values to the main ECU. You will see from other posts that non-standard exhaust set ups can create slow down light situations. Your problem, of course, is that you have lost one bank of cylinders - i.e. the main ECU is protecting one half of the engine because it thinks that a CAT is overheating OR there is completely different reason why one half of your engine is not firing. Since you have a vehicle from which you can swap some parts (and there are some parts like the coil packs you can change over from your own) you can explore the causes which are not directly main ECU related.
Since you are pressed for time. it's beginning to look that you may like to take up the option of a flat bed to the nearest friendly Ferrari agent with the SD2 equipment........

 

We tried my ecu on other 355 last night, it also ran on 4!
I had bought an ecu on fleabay on sunday whilst it was there, and just in case needed etc, for £200.
that arrived this morning, just chasing history on it as it has been opened, which is always a worrying sign as what would you be doing that for? anyway, plugged it in and car runs great on 8 again. left it ticking over to relearn.

happy days.

will get old one looked at in due course, but need to get car sorted now, this has been a bit of a time consuming diversion. thanks all for suggestions.

and a clear lesson here - a slow down light and running on 4 can be the main ecu not the cat controls etc.

 

Good news! Not entirely clear what did the trick. Can you say that it was down to one bad ecu (or two, or was there something else as well?)

 

May last post was not clear - I will try again.........
You refer to replacing ecu's and there is a mix-up (at least in my mind) between cat ecu's and the main ecu. It seem like your problem was solved by fitting a different MAIN ecu. If the main ecu is bad, it can of course give all sorts of problems.
So, can you say that it was just the main ECU that was faulty or did one (or even two) cat ecu's contribute to the problem?
In any case, congrats on getting her back on song. Must be nice to hear eight cylinders prancing again!

 

The cat control units - usually reffered to on here as the cat ecus were both good. as were the temp probes. one lambda sensor was bad with a wire loose, although that is always possible it came loose durign removal as i did look roudn all of the wires before i removed it.
the bad boy was the main ecu unit. it was swapping this that made another car run the same and replacing it made mine run again on 8. hope this clarifies! I think I spent a lot of time on cat units and that area first looking for the problem there, but turned out to be a red herring.

 

Thanks for the clarification - have fun on the track!

 

Cant wait! Bit anxious about competing again after the accident, but got a day on track on wednesday to practice before the weekend which should blow any wobbles away! just got to do seats harness etc etc now, but thats what the weekends for.

 

Thanks for clearing that up.

That is the first time I have ever heard of the Motronic ecu causing a slow down light. But I guess there is a first time for everything. I'm also glad to know that it was something other than what I was suggesting. I really was stumped.

Now did you say that you bought a new Motronic on E-Bay for £200? If so, man did you get a good deal. Are you planning on taking the old ecu apart to find out what is wrong inside? It would be interesting to know what caused the Motronic to flip out like that.

 

Ive got a firm who think they can look at old one and sort it.
fingers crossed, will let you know.

re price of ecu units. later model ones are much cheaper new, eg about £600. earlier ones 1200 plus. found a good source of second hand ones at half price, with replacement if dont work.

 

I thought that he meant the main cat ecu on the 355, not the Motronic fuel injection computer. Don't 355s have 3 cat ecus, a "main" (unlike the 348) and then 1 cat ecu per cat like the 348?

 

I have never heard of a "main" cat ECU on a 355. On the 5.2 cars, there are three cat ECU's for North American cars, left, right and center/bypass. Other markets will have just the left and right cat ECU's. All are the same part number. The Motronic ECU is behind the passenger seat, and I believe that was what the OP said was the culprit.

 

You would have to believe that Motronic 2.7 ecus were selling for £200 to accept that explanation. Possible, I guess.

 

Just thought I would write up a quick summary of my findings re 5.2 ECUs and slow down light saga.
I have now had 4 main ecu units on my car to be able to compare them, and what a difference! You will recall my initial problem was a slow down light that eventually stayed on and cut out a bank regardless of attempts to reset it, new cat control units etc.
Bought a second hand one from fleabay which worked fine, no lights etc, only problem was it had a 7k rev limit on it. Seller didn’t know why claiming he never drove car at high revs.
Tried a friends, he had an intermittent slow down flashing light problem. This went away for short whiles when left to idle and relearn, but came back before too long, it only flashed and didn’t cut bank.
Tried ecus 1 and 2 on his 355 and same issues with them.
Sent ecus 1 &2 away to be looked at and have software reloaded. This they did as well as sort a few dry solder joints they found. Both came back, both with same original problems! So seemed more like a hardware issue in ECU units.
Bought a further second hand unit from prosport for £600. This was in unopened good condition and guaranteed. It worked a treat, no lights, no funny rev limits, just power and smooth running.
Moral of story, don’t spend too long on cat control units searching for problems that might not be in that area. Check main ecu as well as they seem to pick up faults fairly easily.
By way, there is also a difference between early and late 5.2 ECUs, the early ones cost 1200 plus the later 600 new. Sadly, they are not interchangeable.

 

I still think that it's a good idea to eliminate the CAT ecu's as a source of SDL problems BEFORE looking at the main ECU; after all, the cat ecu's are known to have a limited life. I have no way of knowing for sure, but I believe that there can't be many 355's without SLD problems running around with their original CAT ecu's (unless the warning buld has been removed!). I have learned from previous posts that even the newer ones (green potting) can fail.
In any case, thanks for taking the time to bring us up to date. Glad to see that your problems are in the past. Now, you can get tracking (and put the nasty accident experience behind you!).
All the best,
Ron