456 MGT ECU reset can't be performed... | FerrariChat
Buy

456 MGT ECU reset can't be performed...

Discussion in '456/550/575' started by 456enthusiast, Dec 29, 2015.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #1 456enthusiast, Dec 29, 2015
    Hi there,

    As i’ve been having loads of problems with the “Slow Down” light I’ve tried to perform an ECU reset but had no luck: the immobilizer kicks in and forbids me from starting the car from the off position (in order to crank up the engine I need to press the button that enables/disables the alarm/immobilizer).

    As I’m a Ferrari beginner, I’d like to know if any of you experts could shed a light:

    My car is a 456 GTM , 2000 built. Are my ECU’s Motronic 5.2 or 2.7?

    Does the following ECU reset procedure apply to my car ?


    ECU reset procedure.

    1) Turn off all accessories, especially the A/C and radio.
    2) Disconnect the battery using the Battery Disconnect Switch.
    3) Wait until the car is full cold (overnight) or 30 minutes if she is already cold.
    4) Put the key into the ignition and wait 30 seconds.
    5) Turn the ignition to On and wait 30 seconds.
    6) Turn the ignition to Off and wait 30 seconds.
    7) Turn the ignition to On, wait for the Check OK lamp and start the engine.
    8) Let the engine idle for 10 minutes with no inputs
    9) After 10 minutes, you can turn on the A/C and radio, inserting the code if it is a Becker radio.
    10) Drive the car gently for 20 minutes to let all the self-learning procedures complete.

    As written, at point 7 I can’t follow the instructions anymore (the immobilizer needs to be activated and then disabled), any suggestions on how to solve this ?

    About 30 seconds after I start the engine, the “Slow down” light appears. Is the Slow Down light supposed to disappear only at the end of the ECU reset, or should it go when the battery is disconnected ?

    Apologies for my English (I was born where Ferraris are made ☺) and thanks for reading.
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,099
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    #2 Rifledriver, Dec 29, 2015
    That would be because the engine ECU does not control the slow down light. The system that does, does not use memory to control the light.

    Just like any warning light or indicated system failure it will take being diagnosed to repair. At best case on any system, resetting the warning light is a bandaid, not a fix.
     
  3. 360modena2003

    360modena2003 Formula 3

    Jul 11, 2009
    2,437
    #3 360modena2003, Dec 29, 2015
    Check the CAT ECU's - swap them and see if the slow down changes banks.

    These ECUs are located underneath the hood - above the side indicator light.
     
  4. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    39,169
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    #4 tazandjan, Dec 29, 2015
    Your 456M and late 456s have Motronic 5.2 and that does require using the fob to disarm the immobilizer before starting. The immobilizer rearms in 120 seconds if she is not started after using the fob to disarm. Suppose I should have included that step when I wrote that. Like Brian said, though, that is not a problem resetting the Motronic ECUs will fix. In general that procedure is used as a part of a maintenance action involving disconnecting the battery. Even if not used, she will self-learn everything in that procedure after a few drives. Might require cycling the AC a few times, but other than that....
     
  5. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,728
    #5 Mitch Alsup, Dec 29, 2015
    As a 2000, the 5.2 is your ECU, the 2.7s were done in '95.

    Is there a reason you have not downloaded the work shop manual (WSM) ?

    Is there a reason you don't want to take the car to a mechanic to fix the problem or figure out what the problem actually is?
     
  6. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    19,949
    The Cold North
    Full Name:
    Tom
    #6 tbakowsky, Dec 29, 2015
    Resetting the ecu will not fix yo slowdown issue. Diagnose the issue and fix it. It may be costly, it may be cheap. But avoiding a slow down light is asking for a fire if somthing is really wrong with the car.
     
  7. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #7 456enthusiast, Dec 30, 2015
    Thanks for your replies;

    360Modena: Yes i indeed tried to swap the ECU but had no joy. The light keeps showing. How would i know if it changes banks? I guess my model has only one “slow down” signal showing for both banks..(?)

    Rifledriver/ Tazandjan: I appreciate your answers and will try to explain a lil better. I’m assuming there is nothing wrong with the system as the Slow Down light shows up only a few seconds after starting the (cold) engine. I would have thought that, if indeed there was a problem with cats/ thermocouple etc, the light would show after a few minutes at the very least. Is it possibile that a cat overheats only a few seconds from the start (?)


    Tazandjan: So, even though resetting the ECUs might not be beneficial in my case, just for me to know : if at step 7 (Turn the ignition to On, wait for the Check OK lamp and start the engine) prior to starting the engine I activate /disconnect the immobilizer by pressing the button on the fob, that action wouldn’t prejudice the ECU s reset at all?

    Thanks again
     
  8. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #8 456enthusiast, Dec 30, 2015
    Thanks for your answers.

    Mitch: I'd appreciate if you furnished me with a link to download the workshop manual.

    I did take the car to my (Porsche) mechanic but he suggested that i took it to Ferrari, which means driving the car to Rome (400 Km from where i live). Hence, before doing that, i thought that i'd rather try the "simple" steps by myself.

    Tbakowsky: I appreciate your answer and will try to explain a lil better. I’m assuming there is nothing wrong with the system as the Slow Down light shows up only a few seconds after starting the (cold) engine. I would have thought that, if indeed there was a problem with cats/ thermocouple etc, the light would show after a few minutes at the very least. Is it possibile that a cat overheats only a few seconds from the start (?)
     
  9. Alden

    Alden F1 Rookie
    Rossa Subscribed

    Apr 25, 2010
    3,604
    Central Florida
    #9 Alden, Dec 30, 2015
  10. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    39,169
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    #10 tazandjan, Dec 30, 2015
    Yup, does not affect the ECU reset at all. Plus she obviously will not start without the immobilizer being disarmed.
     
  11. 348SStb

    348SStb F1 Rookie
    Owner

    Apr 9, 2004
    2,991
    Palm Beach County, FL or Nassau County, NY
    Full Name:
    Dave
    #11 348SStb, Dec 31, 2015
    Last edited: Dec 31, 2015
    paradox0987: what is your name? What is your location? Perhaps you'd like to fill out your profile?

    The above advice is great advice. I will expand further.

    The "Slow Down" light is triggered by the "thermocouple control module," which is also known as a cat ECU," "calayzer ECU," "exhaust ECU." The calayzer ECU gets temperature information from the thermocouple, which is basically a temperature sensor.

    As there are two banks of cylinders, there are two catalyzer ECUs. So swap the catalyzer ECUs left and right and see if the Slow-Down light appears on the dashboard for the opposite cylinder bank. If it does, then you know to replace the catalyzer ECU.

    If the Slow-Down light stays on the same cylinder bank, then you could have a bad thermocouple. There are quite a few of these (at least two per cylinder bank, maybe more). Diagnosing a bad thermocouple would be a bit more complicated, as you would have to (very carefully) swap all the thermocouples left to right before you can try to isolate the thermocouple that's bad.

    Don't use the engine ECU reset trick to solve your problems... it masks the problem. Not a good idea to execute that procedure very often.
     
  12. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #12 456enthusiast, Dec 31, 2015
    Last edited: Dec 31, 2015
    Hi there 348SStb

    Profile's been filled.

    I indeed tried to swap the ECU but had no joy. The light keeps showing. How would i know if it changes banks? I guess my model has only one “slow down” signal showing for both banks, in the middle of the dashboard ..(?)

    I found this information on several posts:


    "the 456M GT has two Motronic 5.2 ECU's, buthe SLOW DOWN LIGHT in the dash is common, so as a driver you have no idea which back is giving you trouble...

    The older cars has a light for each bank...much easier and user friendly..."
     
  13. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #13 456enthusiast, Dec 31, 2015
    Thanks for the link, Alden. I did manage to make a few hundreds km (everytime the car would start limiting the fuel I'd stop and wait for a few minutes, then go again for about 100 km and again...) a bit of a nightmare but i found it doable.
     
  14. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #14 456enthusiast, Dec 31, 2015
    Last edited by a moderator: Sep 7, 2017
  15. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    19,949
    The Cold North
    Full Name:
    Tom
    #15 tbakowsky, Dec 31, 2015
    Easiest and cheapest way is to swap the ecu to the opposite side and see if the issue follows. If it does not, then swap the thermocouples from side to side. If the issue follows then you have found your issue and replace the part that is defective.

    If it does not follow, then further and deeper diagnoses will need to be done.
     
  16. craterface

    craterface Formula Junior

    Apr 14, 2011
    622
    Sanibel Island, FL
    #16 craterface, Dec 31, 2015
    Last edited: Dec 31, 2015
    It could mean just the Catalyst ECUs are bad--these are not the same as the main ECU. There are two, and they frequently fail due to high heat under the hood or moisture intrusion. Eurospares UK sells them at a reasonable price. If they have not failed yet on your car, they will. This is what caused the "slow down" light on my 2000 550.

    The thermocouples are also a failure item, giving a "false" slow down light.

    Or, you may have a misfire resulting in unburned fuel going out the exhaust and into the catalytic converter. The catalyst is very hot normally, so this fuel can ignite and burn your car to the ground. This is why the light says "slow down" and why the manual says that when you see this light you should stop driving the car.

    The slow down light will come on every time you start the car until you diagnose and fix the problem.

    Good luck
    Scott
     
  17. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #17 456enthusiast, Jan 2, 2016
    I did try to swap the ECU's but that didn't solve the problem. Will try to switch the thermocouples sensors as well. I've just remembered that the Slow Down light first showed right after i hit the bottom of the car on a garage exit ramp. Is it possible that one of the thermocouples wires (which, if i well understand are located by near the exaust) were hit, hence the problem?. At the time i went to my mechanic and asked to have a look to the Lambda sensors (which were fine) but didn't know that the thermocouples are located in the same area...
     
  18. 456enthusiast

    456enthusiast Karting

    Jul 23, 2011
    98
    UK / Italy
    #18 456enthusiast, Jan 2, 2016
    Thanks Scott, I've just remembered that the Slow Down light first showed right after i hit the bottom of the car on a garage exit ramp. Is it possible that one of the thermocouples wires (which, if i well understand are located by near the exaust) were hit, hence the problem?. At the time i went to my mechanic and asked to have a look to the Lambda sensors (which were fine) but didn't know that the thermocouples are located in the same area...
     

Share This Page