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97's F355 - "Slow Down" light is blinking

Discussion in 'Technical Q&A' started by yfc, Jun 25, 2004.

  1. yfc

    yfc Karting

    Dec 23, 2003
    212
    Geneva / Switzerland
    Full Name:
    Christophe
    Yesterday I pick-up my (European) F355 97 (36’000km) from the annual service (oil, …, not a big one with the distribution belt). In addition to the standard maintenance, the mechanical had to grease the by-pass valve who seams to remain closed.

    After driving only 2 km, I got the “Slow Down” warning light blinking. The water and oil temperature were quite normal (far below the red zone).
    The engine was running fine from cold to normal working temperature. I did not noticed any misfired, strange engine noise nor problem to revs the engine.

    I went back strait to the Ferrari garage who checked the error codes (from the 5.2 Motronic). Both left and right CATs where in error (overheating).

    No need to mention that I never had this problem before I brought the car to the service! This even when I used to be stuck in traffic jam (where the engine temp use to be higher).

    Since both the car outside as well as the plastics parts of the engine bay (ie. air filter, lateral shock absorbers panels protection, … ) has been washed by Ferrari, I wonder if I’m not facing an electrical problem. It’s effectively surprising to suddenly get both CAT in errors! I therefore rather suspect a false error caused by the system controlling the CAT (ie ECU).

    Could water have reached the electrical contact of the ECU, of the CAT sensor, … ?

    Does anyone have an idea of the possible cause of this “Slow down” overheated CAT problem?

    Thanks in advance.

    Christophe.
     
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  3. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
    Full Name:
    Malcolm W
    Christophe,

    You have mail

    MW
     
  4. goyal99

    goyal99 Karting

    Mar 5, 2002
    185
    Upstate NY - USA
    Full Name:
    V K
    I would check the exhaust ECU contacts and clean them with a small wire brush...Then clean the contacts with electrical cleaner (from your local auto parts store). You can also apply Stabilant (if you have it) which promotes the energy transfer between electrical contacts in plugs...I've used it and it works.

    You can do a search in the Archives about Stabilant and what it does....I had to order mine thru the mail. Your local Auto parts store most likely doesn't carry it but since you're in Europe maybe they do...

    Anyway, the water issue getting into the engine bay while washing the car is valid. I had a couple of corroded ground contacts on my engine bay...A good cleaning with a steele wire brush and contact cleaner should do the trick...

    Also you can always disconnect your exhaust ECUs to see if the "Slow Down" light goes away (just for testing pursposes)...If your still have cats on the car I would leave them connected.

    Cheers - VK
     
  5. yfc

    yfc Karting

    Dec 23, 2003
    212
    Geneva / Switzerland
    Full Name:
    Christophe
    Hi guys,

    Thanks to your reply, I found out that my exhaust by-pass valve was sticking in the open position. Hence the louder noice at low revs and the "Slow Down" light.

    Bye for now,
    Christophe.
     
  6. W00dEar

    W00dEar F1 Rookie
    BANNED

    Feb 24, 2004
    3,515
    LI, NY
    Full Name:
    Chris
    what is the downside of disconnecting exhaust ECU for extended period?
    btw i have no CAT, testpipe is in place, and i get the slowdown light every now and then.
     
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  8. yfc

    yfc Karting

    Dec 23, 2003
    212
    Geneva / Switzerland
    Full Name:
    Christophe
    The CAT ECU is protecting the CAT from overheating. They are also responsible of controling the Motronic injection to optimize the air/petrol mixture. The objective being to get the cleanest possible exhaust gaz (accordingly to the regulation).

    If the Motronic is not getting the feedback from the pre and post CAT O2 sensors, how will the Motronic adapt the petrol quantity? Would the mixture be to rich or to poor? Would it dammage the CAT?

    One of my friend did remove the CAT on his Testa. He also remove the CAT sensor thinking it was no more needed.
    The Ferrari mechanical (a good one) advised him to leave the CAT sensor in place. This to don't "disturb" the Injection.

    So ... what should you do? I would say, keep the sensor apart if you have had the Injection being re-programmed (by the way, is it possible?).

    I hope this will help.

    Bye for now,
    Christophe.
     

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