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355 ECU problem solved

Discussion in '348/355' started by 355NY, Jul 25, 2008.

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  1. 355NY

    355NY Rookie

    Aug 12, 2007
    34
    #1 355NY, Jul 25, 2008
    A while back I posted a thread on an ECU code problem. Intermittent 1-4 slowdown and eventually constant 1-4 slowdown. The 1-4 slowdown would come on immediately upon starting the engine cold. Here's the diagnostics I did to solve the problem. BTW, First major service performed within the past 200 miles (engine out, belts, wires, Hyperflow Cats, 02 sensors).
    1. switch thermo ECU's (L & R) - no change, 1-4 slowdown
    2. switch thermo sending units from Cats (L & R) - no change, 1-4 slowdown constant
    3. switch Motronics (L & R) no change, 1-4 slowdown
    4. unplugged two plugs to ECU, 1-4 slowdown light on, but the engine ran fine
    With the above eliminated, it could only be in the harness. Couldn't be the sending unit plug from the CATs because that was switched. Only plug was from the thermal ECU to Motronics. Performed wiggle test with engine running and light on. Slowdown light flickered. Stopped the engine and reset all the connections in the plugs (slight pulled out and bent). Reattached after going over all the connections with Stabilant 22.
    My take is that one genius mechanic in undoing that connection, instead of releasing the clip, pulled on the wires. This pulled the wires out on the connector. Very sloppy.
    I hope this helps those with a 1995 Motronics 2.7. I believe this was the last year that was used.
     
  2. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,044
    USA
    #2 f355spider, Jul 25, 2008
    Last edited: Jul 25, 2008
    Connector problems are an issue with ALL year Ferraris, and only seems to get more troublesome as they age. Glad you figured yours out. ;) Same type connectors on all year 355's....and on 360's.
     
  3. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,614
    The Brickyard
    Full Name:
    The Bad Guy
    #3 ernie, Jul 26, 2008
    It wouldn't surprise me.

    Thanks for the update.
     
  4. 355NY

    355NY Rookie

    Aug 12, 2007
    34
    #4 355NY, Jul 27, 2008
    BTW, Ernie, you've been incredibly helpful in keeping my 355 running smoothly. Thanks. Mike
     
  5. conscom

    conscom Formula Junior

    Jan 6, 2008
    467
    Vancouver BC Canada
    Full Name:
    Gary
    #5 conscom, Jul 27, 2008
    Thanks for the info altho as I'll keep it for reference if , god forbid, it shoudl happen to me in the future. Great post.
     
  6. 355NY

    355NY Rookie

    Aug 12, 2007
    34
    #6 355NY, Jul 28, 2008
    Gary,
    Seems that the connector problem is popular. Stabilant 22 is good for corroded connections (that sounds ominous, but water getting in does the deed). Can't wash 355's by spraying water over the engine. I know that, but the kid Ferrari hires to wash the car after they do a $13k service doesn't. Serious detective work is the answer. This forum is incredible for that. Hope you don't have to go through what I did although it turned out to be a faulty pin connection.
    Mike
     
  7. 355NY

    355NY Rookie

    Aug 12, 2007
    34
    #7 355NY, Jul 28, 2008
    BTW, all the diagnostics I did on my 95 355 took maybe total 30 minutes. Switching the thermal ECU's, the thermal CAT sending units and finally the Motronics are a few bolts each. It's 30 minutes of detective work that will save a ton of dough. Mike
     
  8. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,614
    The Brickyard
    Full Name:
    The Bad Guy
    #8 ernie, Jul 28, 2008
    Last edited: Jul 28, 2008
    Glad I was of help. I'm just returning the help I got when I first got my 348, cause I didn't know squat, and still don't.
     
  9. conscom

    conscom Formula Junior

    Jan 6, 2008
    467
    Vancouver BC Canada
    Full Name:
    Gary
    #9 conscom, Jul 30, 2008
    Last edited: Jul 30, 2008
    Hi Mike,
    In my case, I did all the detailing of engine, engine bay, etc. and was very careful to prepare by wrapping all elec. connectors with plastic, etc.. I actually cleaned the engine bay with a toothbrush and rag, rinsing only with a spray bottle! I also used an equivalent to Stabilant 22 that I used on my boat on all the connectors. I tried to eliminate all the obvious and least expensive first. I did have the engine check lights coming on intermittently after the service but was corrected after replacing the plugs and crankshaft sensors. I also replaced the O2 sensors and plug wires as well. Since I'm planning to keep the car for a while at least, might as well replace for peace of mind. And the clean tail pipes also indicate it's running better. Now waiting for my camshhaft sensors which should solve my cold starting problem. My whole problem was basing my purchase on the 30k having been done by ZR Auto 4,000 mi. ago in Sep.'06. The previous owner only got a partial but charged for a full.
     

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