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360 thermocouple resistance (Slow Down warning)

Discussion in '360/430' started by artsd, Dec 23, 2019.

  1. artsd

    artsd Karting
    Silver Subscribed Owner

    May 6, 2009
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    Art
    Getting flashing Slow Down upon cold start which turns into solid Slow Down after several minutes of idling. Got error codes P1449 (catalyst temperature bank 2) and P1454 (catalyst protection active bank 2). Cat is definitely not hot.

    I am trying to determine if I have a bad thermocouple or a bad cat ecu. Can I figure that out just by measuring the resistance of the unplugged thermocouple? What resistance should I see at various temperatures?

    If one side goes bad, does that mean the other isn't far behind? Should I just replace the cat ecus and thermocouples on both sides? Technistrada has their own cat ecu for $189 and thermocouple for $29 which is a very reasonable price.
     
  2. Motob

    Motob Formula 3
    Professional Ferrari Technician

    Nov 11, 2003
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    Brian Brown
    A thermocouple does not change resistance with temperature. It creates voltage depending on the temperature. I would recommend swapping the ECUs from one side to the other and see if the fault changes to Bank 1. If it does you know that that ECU is bad. If it stays the same, then you know that the bank 2 thermocouple is bad.

    Brian Brown
    San Francisco Motorsports
     
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  3. artsd

    artsd Karting
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    Thank you Brian. I think the references I saw to testing thermocouple resistance was to determine if there was an open circuit or not which might be somewhat useful to know. I will give the ecu swap a try. Thanks.
     
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  4. Motob

    Motob Formula 3
    Professional Ferrari Technician

    Nov 11, 2003
    2,149
    Berkeley, CA
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    Brian Brown
    Yes, you can test if the wires to the thermocouple or if the thermocouple is broken inside using an ohmeter, a good first test. But there is no correlation between resistance and temperature with a thermocouple.

    Brian Brown
    San Francisco Motorsports
     
  5. artsd

    artsd Karting
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    Thank you. I had a fundamental misunderstanding of how a thermocouple works but it is clear now.
     
  6. 24000rpm

    24000rpm F1 Rookie
    Silver Subscribed

    i've replaced 4 bad cat ecus on the 360s. Never had a thermocouple failure.

     
  7. 360trev

    360trev F1 Rookie
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    Oct 29, 2005
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    360trev
    The Bosch ignition ecus actually have an estimation model for catalyst temperature built in based on what's going on with the oil, coolant, etc. Its therefore possible to swap over to use that modelling rather than use an external cat ecu and thermistor. In fact Ferrari opted to do exactly this on later spec F430s. I can look into this further if you want me to.

    Already the Ferrari SAK tool I developed can delete them entirely along with the cat monitoring ecu which just converts the signals from the thermistors to a voltage the ecu can handle. Result is you can delete both the thermistor and control station and no CELS or slow down.

    More often than not the issue is with the system itself rather than massive over fueling caused by defective ignition system components like coil packs, spark plugs or fuel injectors. The system is really trying to protect the cats from damage when too much fuel is entering them and burning causing them to glow red.

    It's Really quite easy to see if anything has failed in such a way as cat on one side will be glowing red and not on other bank. Cats on F430 tend to glow anyway BTW and isn't cause for concern.

    If its a cold start and problem comes on its definitely a problem with the monitoring. Either wiring, thermistor itself or cat control station has failed.
     
  8. artsd

    artsd Karting
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    #8 artsd, Jan 1, 2020
    Last edited: Jan 1, 2020
    I finally got around to swapping the left/right cat ECUs. I am now getting error code P1446 whereas originally I got P1449 and P1454.

    The error code docs I have say P1454 is "catalyst protection active (bank 2)". But my docs for P1446 say just "catalyst protection active". Can I assume that P1446 is for bank 1? If so, looks like I have one bad cat ECU but for the price I think I will buy 2 from Technistrada and keep the spare one on hand.

    And here is an even dumber question than my original one. Which side is bank 1 and which is bank 2? For some reason I thought bank 2 was the left side (US driver's side) but now I am questioning myself.
     
  9. SonnyCrocket

    SonnyCrocket Rookie
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    May 26, 2018
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    #9 SonnyCrocket, Jan 4, 2020
    Last edited: Jan 4, 2020
    To to the OP, I had a similar issue and opted for the Technistrada ECUs. No issues and quite happy with the cost.

    FYI- There were no signs of degradation on the green resin ECUs that I replaced, but after confirming a good ground and thermocouple, I felt confident the ECU was at fault.
     
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