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456GT - What reasons for "7-12 Check Engine" warning light?

Discussion in 'Technical Q&A' started by joelk, Feb 2, 2004.

  1. joelk

    joelk Rookie

    Nov 1, 2003
    35
    Hi all,

    Does anyone have any suggestions on what could be causing the "7-12 Check Engine" warning sign on my dash instument panel, to be staying on?

    What could I (an amateur) check for myself, before I hand it over to the local (expensive) garage? It's on a 1994, 456GT (5.5 V12).

    Any thoughts or suggestions much appreciated...

    Many thanks!

    Joel.
     
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  3. Napolis

    Napolis Three Time F1 World Champ
    Honorary Owner

    Oct 23, 2002
    32,118
    Full Name:
    Jim Glickenhaus
    It could be a faulty sensor or it could mean that the cat is getting so hot that's it's about to start a fire.
     
  4. rudy

    rudy Formula Junior

    Jan 13, 2004
    360
    Los Angeles California
    Full Name:
    Rudy Hassen
    Most good garages will charge nothing or very little to read the codes. DO NOT ASSUME THAT WHAT THE CODE SHOWS NEEDs REPLACEMENT. If it says th O2 sensor, you may or may not need an O2 sensor. It could be dozens of other things in the O2 circuit. Even Pep Boys can read the code for you.
     
  5. donv

    donv F1 World Champ
    Rossa Subscribed Owner

    Jan 5, 2002
    19,968
    Portland, Oregon
    Full Name:
    Don
    I think the cat getting hot light is the "Slow Down" light.

    I had a similar problem with my 456, and the only real solution was to take it to the dealer and have them hook it up to the computer, so they can tell why the light is coming on.

    Does the car seem to run OK?
     
  6. GTB4NART

    GTB4NART Formula Junior

    Jan 17, 2004
    421
    If it comes on after 15 minutes of driving it could be hot cats, however, on my 1995 456, they go on and off when I hit bumps sometimes. They have a mind of their own. If they flash, then there's trouble (so I've heard). Again, if it comes on when you first start the car (cold) and stays lit, it's probably an o2 sensor.


     
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  8. donv

    donv F1 World Champ
    Rossa Subscribed Owner

    Jan 5, 2002
    19,968
    Portland, Oregon
    Full Name:
    Don
    One thing I forgot-- you can try resetting the ECUs by removing all power to the car (use the battery shutoff) for 15-20 minutes, and then start it up and let it idle for 15 minutes without touching the gas.

    This didn't solve my problem, but you never know.
     
  9. joelk

    joelk Rookie

    Nov 1, 2003
    35
    Hi fellas,

    Cheers for the advice... Had to take it into the dealers today as I'm taking it on a long road trip to Scotland tomorrow. They thought the engine was sucking in too much air, but they didn't know why. They reset the settings and it's ok again. £180 for the privilege. Robbing Basxxrds. No-one ever said Ferrari ownership comes cheap!

    Regards,

    Joel
     
  10. Onlinesys

    Onlinesys Formula Junior

    May 1, 2002
    425
    Hong Kong
    Hi Guys,

    Glad to hear you solve the problem by just reseting the code through the dealer's computer. It's about the same cost over here in Hong Kong around HK$3,000.00 (US$380.00)!!!

    While quite a lot of you guys own 1994-1995 456Gt. I would like to enquire if anyone of you had paid for the Cambelt change process and/or 30k major maintenance.

    There seems no one over here has any first hand experience at all.

    Cheers.
     
  11. GTB4NART

    GTB4NART Formula Junior

    Jan 17, 2004
    421
    Ron Tonkin Ferrari in Portland, OR does the 30k on a 1995 456 for about $5k - Orange County Ferrari will do just the belts and tensioners for $2k. I am awaiting belts and tensioners to arrive for my 456. I plan on installing them myself. I still need to find out exactly how the tension for the belts is checked - the service book says to use the Staeger Tensiometer on the accessory belts but not the cam belt. It appears that the cam belt is under spring tension that is factory set (the stiffness of the spring).

     
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  13. Diablo

    Diablo Formula Junior


    Good Luck!!!

    I have seen it first hand, while taking the belts off of the V-12 or even putting them back on, the cam rotate about 30 degrees.Due to the tension of the lifter and lobe of the cam.
    It bends the valves!!!!

    All I am saying is be very carefull doing a V-12 service yourself.
    Taking the heads off is not very fun. Neither is replacing the valves.
     
  14. GTB4NART

    GTB4NART Formula Junior

    Jan 17, 2004
    421
    Turns out that the Staeger Tensiometer is required for the cam belts. The tolerances are very tight with the v12 - 1 degree. If your two degrees off, you get check engine lights all the time. The cam must be locked down and the new belt positioned appropriately. The key to the job is patience and a "measure twice, cut once approach."

     
  15. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
    Full Name:
    Rob Schermerhorn
    FYI,

    The amber 'check engine' MIL (malfunction indicator lamp) does not, will not, indicate catalyst melt-down. That's what the red 'slow down' MIL is for.

    Yes, the slow down (red) MIL may only be a thermocouple control unit malfunction. The 'slow down' MIL system contains a thermocouple, which uses a bi-metallic sensor to transduce temperature into an electrical signal. Then, the thermocouple control unit (a.k.a. thermocouple ECU) converts this signal into one that the Motronic engine ECU can understand.

    The amber check engine MIL will indicate many other potential errors, as noted in the WSM (workshop manual). One of the usual suspects is the Lambda circuit (oxygen sensor), which monitors the exhaust for oxygen molecules (aka excess-air factor). However, there are many other sensors which may trigger an MIL.

    Proper diagnosis is the only way to permanently fix the malfunction. There certainly may be situations which trigger an MIL which can temporarily rectified by resetting the error codes, erasing the error memory by disconnecting the battery momentarily (3- 5 seconds). If one chooses to perform this operation, you should follow up by re-initializing the self-learning Motronic by starting the engine without touching the throttle for approximately 5 minutes. Waiting until the cooling fans come on is a good reminder that enough time has elapsed. The ECU is learning throttle position during this operation.

    If you choose to erase error codes without reading them, this may hinder proper repair of the malfunction. It's good data that should be collected.

    USA cars may access the MIL codes without a computer interface via pushing the button located near the Motronic unit for > 10 seconds, then reading the error codes as flashes of the amber MIL. The error memory may also be reset using this method. Additional information is located in your car's WSM (always a good investment).

    Typically, disregard the crankshaft position sensor error, this is triggered because the engine is not running at the time you're accessing the error codes.

    This only applies to OBD I cars, up to 1995.


    Best regards,

    Rob Schermerhorn
     
  16. donv

    donv F1 World Champ
    Rossa Subscribed Owner

    Jan 5, 2002
    19,968
    Portland, Oregon
    Full Name:
    Don
    That's great info Rob, thanks!
     
  17. sunburn

    sunburn Formula Junior

    Nov 2, 2003
    693
    Dawsonville, GA
    Full Name:
    Rick R.
    Joel,
    I had a similar problem on my '95 456GT about a week after I bought it. I fixed mine by re-seating the connectors on the ECUs.
    Turn the battery disconnect off. Remove the drivers side and passenger side kick plates and disconnect the large connectors that attach to the ECUs. I used contact cleaner (from Radio Shack) to spray the connector assemblies and then re-connected, disconnected and re-connected the ECU plugs a few times.
    When the plugs are re-connected and the battery switch turned on, start the car WITHOUT touching the gas pedal and let it idle for about 10 minutes so the ECUs can re-learn the throttle settings.
    My warning light has been dark ever since.

    Rick . . . .
     

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