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599 ambient air temperature

Discussion in 'Technical Q&A' started by omulec, Feb 19, 2021.

  1. omulec

    omulec Rookie

    Nov 26, 2008
    32
    That seems to be not really model specific, but maybe someone will give a hint here.

    599, as most of Ferrari models has an ambient temperature sensor under driver mirror. The temperature on the dash is displayed properly outside +19,5 Celcius deg. Both heads however show in parameters -40,5 Celsius deg. That looks evident like sensor failure, but the dash show correct temp.

    Now - any idea if there is some other temp sensor that I miss, or there might be something strange with the one in the mirror? I know that signal goes threw the driver door node (that control also the power windows, but I'm not sure that this device separates the reading of the temp...
     
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  3. Qavion

    Qavion F1 Veteran
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    Feb 20, 2015
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    Ian Riddell
    Interesting. Looking at the wiring diagrams for the F456M and 550, I've just realised that the undermirror sensor wiring only feeds the HVAC ECU. The HVAC system must process the signal and send the temperature data to the instrument display. Perhaps the 599 is similar?

    Not sure what you mean by heads? The engine ECUs? Do the 599 engine ECUs receive ambient temperature from the mirror or by, typically, an IAT sensor (inlet air temperature sensor)?

    -40.5C is an indication of an open circuit on a temperature sensor or that the sensor is not active (i.e. not fitted on this model). On some V12's, for example, there may be only one kind of temperature sensor feeding both engine ECUs. The sensor is connected to one ECU only and the data is sent to the other ECU on an inter-ECU CAN bus or via plain wiring. If you are interrogating one of the ECUs using a generic OBD2 reader, the display may show two values for temperature. One value will be normal, the other will be -40.5C (indicating it's not fitted). I'm not sure what it means if both are showing -40.5C. Are you getting any warning lights? Your IAT may be faulty.
     
  4. omulec

    omulec Rookie

    Nov 26, 2008
    32
    Correct - i mean engine ECUs. There are 2 - one for each head. The engine check error is present on the dash - p0072 and p1114. Than Galileo reads -40,5 on both banks as I said (there is only one ambient air temp value on each bank ECU). I was quite sure, that what you call IAT sensor is a part of MAF sensor on 599.
    But it happened suddenly - they would have to fail both sides at the same time, which would be quite odd.

    That's why I was asking for a clue if there are some other sensors that feed the engine ECU with the ambient air temp. If anyone is sure that it's MAF, or anything else, I would appreciate any hint.
     
  5. Qavion

    Qavion F1 Veteran
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    Feb 20, 2015
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    Ian Riddell
    Now I'm with you, but I'll have to leave this to the experts. Even if the temp sensing was done by the MAFs and the MAFs were identical, there is no guarantee that the temperature function is normally enabled on both sides. The wiring might be different on each bank.

    If only one is active, then one could fail and take out both sides.
     
  6. omulec

    omulec Rookie

    Nov 26, 2008
    32
    I found out that there is a problem with driver door node (i.e. power windows issue). And I believe the temp signal from the mirror sensor is going threw that node. Just waiting for a replacement to check that. Maybe the node split the signal to the dash and engine ecu's...
     
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  8. omulec

    omulec Rookie

    Nov 26, 2008
    32
    Just to confirm the issue, as the new driver node arrived. It was what I suspected: the engine ECU recives the ambient air temp from mirror sensor via driver door node. And the driver node splits the temp read to send separately to dash and engine. Fixed, working.
     
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