p1448 OBII code | Page 4 | FerrariChat

p1448 OBII code

Discussion in '348/355' started by Labman, Apr 4, 2011.

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  1. Qavion

    Qavion F1 World Champ
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    We hear that Goth designed a dummy TCU for the bypass valve using a single voltage output. Hence my theory.
     
  2. Qavion

    Qavion F1 World Champ
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    Agreed, but the WSM doesn't mention a temperature decrease. We just assume it's part of the fault logic because to us it is common sense.

    However...

    John, I thought you'd been around the forums long enough to know of Goth's experience with this stuff. So how does pulling the vacuum line not generate a code in our common sense logic?

    We are not trying to overcomplicate things, we are trying to make sense of all the information presented to us. Scientific Method throws out theories if they don't satisfy all the criteria.
     
  3. johnk...

    johnk... F1 World Champ
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    Jun 11, 2004
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    I'm just trying to be pragmatic about this. I've pretty much learned to ignore what has been written about things here. Too many people, with good intentions, throw out too many ideas that just cunfuse the issue.

    It may be that the ECU may just be looking to see if the BP is open when it is supposed to be and not worried about it when closed. Thus, maybe it only looks for a "hot" condition. In that case a 1448 code would mean the BP is not opening, assuming the sensors are working. Thus, given that everything on the TC and TCU side seems to be working, check BP operation with some vacuum source, check the operation of the solenoid, check wiring, check for ECU signal to solenoid, check for vacuum leaks, check for proper vacuum level. All are pretty easy except checking for the signal from the ECU. This could be done by wiring a volt meter in the circuit and looking for a voltage applied to the solenoid while driving under condition when the BP should be open.

    There are so many mixed reports of what happens when. As for pulling off the vacuum hose from the BP valve, I think that has been proven to be bogus.
     
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  4. Qavion

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    @Carmellini I've forgotten if you've changed or interchanged the solenoid valve. There have been reports of connector pin corrosion problems and solenoid valves slow to reclose. You have checked the bypass valve on the bench, but maybe it's not fully closing when it's hot. Finding a way to fit a camera under the engine lid may be the only way you'll know for sure.
     
  5. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    814
    A bit premature, but thought I would report: I found a 4th green TCU in my spares box and tried that one out with exact result. The pending 1448 trips within a few miles. Also, no idea if this means anything, when the code gets stored, the freeze frame data always displays RPMs under 3,000.

    No, I have not touched them, yet.......planning on looking at them tomorrow. I did inspect the vacuum hoses and they look good and properly connected.

    My solenoid to the outboard RH side has a black connector, and the one inboard towards the LH side has a blue connector. Is that the correct orientation?

    FWIW: I found a 4th green TCU in my spares box and tried that one this AM with same results. The 1448 code goes pending in only a few miles, but then gets stored a good number of miles later. No idea is the freeze frame data matters, but it always show under 3000 RPMs?
     
  6. Qavion

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    It's still hard to make a guess from this. According to the WSM, the lowest valve actuation rpm is around 2760rpms and the highest around 4000 rpms. So the message could either be appearing at 3000 rpm because the valve is not opening fast enough or not closing fast enough (due to various reasons). i.e. sticky bypass valve, weak vacuum, sticky solenoid valve. It would certainly help with the diagnosis if we knew exactly what the fault logic was.

    Anyway, because the pending message happened so early, it may exclude a sticky bypass valve (due to heating). In which case, I would change/interchange the solenoid first.
     
  7. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
    814
    Not sure what you mean? Swap the blue and black connectors? Could they be plugged in incorrectly?

    Also, does EVERYONE with CAT delete get a 1448 or is it just a coin toss?
     
  8. Qavion

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    #83 Qavion, Feb 19, 2021
    Last edited: Feb 19, 2021
    Sorry, meant to say the interchange solenoid positions (as it's probably not possible to re-route the vacuum wiring). You would be getting Secondary Air-related messages if you had the electrical plugs accidentally swapped over.

    The blue plug is supposed to be on the secondary air solenoid. The secondary air solenoid is supposed to be the outboard solenoid (The one closest to the vacuum reservoir)
     
  9. Qavion

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    Actually, you may be able to swap over the electrical plugs and the two top pipes on the solenoids for faultfinding purposes (i.e. without interchanging the positions of the solenoids). The bottom two pipes are just for vacuum.
     
  10. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
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    My vacuum lines are connected as in your picture, but my blue connector is attached to the inboard solenoid???


    ....but I don't have any secondary codes.....hmmmmm
     
  11. Qavion

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    Then I would confirm that the corresponding vacuum plumbing goes to the right components.

    i.e. the top vacuum pipe of the solenoid with the blue plug goes to the secondary air valve.
     
  12. Qavion

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    Perhaps because your vacuum plumbing has also been swapped over (in the dim, dark past)? Maybe it was done by a previous owner for faultfinding purposes.
     
  13. drbob101

    drbob101 F1 Rookie
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    Nov 26, 2012
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    I’m going out on a limb here because I don’t really know this and no one really does but the techs who programmed the motronics 25 years ago, the vacuum system voltages have no bearing on the CEL and 1448 code

    The SDECU and the thermocouple measure temperature and transmit .
     
  14. Qavion

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    Not sure how you'd prove it either way. I guess putting a voltage checker on the solenoid coil circuit would be somewhat redundant when you already have the bypass TC to measure the performance of the entire system.
     
  15. Skippr1999

    Skippr1999 F1 Rookie
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    Just a bit more info from my past issues with 1448.

    I installed a Capristo Bypass valve which came with it’s own solenoid. This was the 1st change I made to the the exhaust system. Everything was fine until I later installed Tubi headers and Tubi test pipes. It was only after the header swap and removing the cats that the 1448 was triggered. At the same time, I installed Big Daddies extenders. The Big Daddies worked and I never have gotten any cat codes. The 1448 was the pest that I could never get rid of. The Capristo techs said their bypass valve could not be used without cats. They felt it had to do with exhaust flow and temperatures triggering the 1448. Without the cats and freer flowing headers the temperatures were probably too cool.
     
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  16. Skippr1999

    Skippr1999 F1 Rookie
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    Do European cars have CATS and bypass valves ? If not, is their ECU programming different ? Could a tuner do ECU coding to rid the system of 1448 ?
     
  17. Qavion

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    According to the parts manual, there are a couple of 5.2 ECUs (F1/non-F1) designed for no-cat cars, but you might want to ensure that they are compatible with your other still-fitted pollution gear. I see all 5.2's have a secondary air injection system. According to Wiki, the primary function of the secondary air system seems to be to heat up the cats faster (where cats are fitted), but they still seem to reduce pollution on non-cat cars.

    https://en.wikipedia.org/wiki/Secondary_air_injection

    Carmellini tells me that the ECUs can be reflashed, but I'm not sure if this reflashing takes care of the bypass fault message (?)
     
  18. Carmellini

    Carmellini Formula Junior

    Jul 16, 2019
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    Mase engineering (https://maseflash.com) told me they could do this, but it they do not do a lot of work on pre MY 2000 cars
     

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