How to flash VIN to used PCM?

Discussion in 'General Motoring' started by carbide, Nov 17, 2006.

  1. carbide

    carbide Guest

    1998 Grand Voyager, 3.3L engine. My PCM ( powertrain control module )
    died a while back, and I was able to find a used one quite
    inexpensively. I installed it and it worked just like before. It was
    from a Dodge Grand Caravan, but had the same part number as my
    Plymouth, 4727154AJ.

    Now it's time to smog it, and I know the VIN not matching is going to
    be a problem.

    Anyone have any experience changing the VIN? I understand it can be
    done with a DRB III scanner, but I expect the dealer is going to tell
    me it can't be done or some such, which may or may not be true.
    carbide, Nov 17, 2006
  2. Why don't you start by going to the dealer, telling him your story,
    and asking him about it?

    Did you save the old PCM? Maybe if it has a socketed rom chip
    you can just take the rom from the old one and put it in the new one.

    Frankly, I cannot imagine the smog check is going to care. They
    use the VIN number to determine engine size and such, and since your
    PCM came out of a GC that presumably had the same engine, when
    they key either VIN into the test computer, it's going to setup the
    test computer with the same testing levels.

    Ted Mittelstaedt, Nov 18, 2006
  3. carbide

    carbide Guest

    I asked for an appointment online, and filled in the details on the
    online form. I'm waiting for them to get back to me. While I'm waiting,
    I thought I'd find out what I could. I did find a procedure online for
    initializing a new PCM. If there's not a VIN number, the DRB III tool
    prompts you to enter one.
    I saved it, but the circuit board is down in a cast housing and under
    an inch of tough rubbery potting compound. I'm an electronic tech and
    might have been able to fix it myself if it weren't for that. These
    use surface mount flash memory chips, not old fashioned socketed ROM's.

    Heh heh! Part of the price of living in paradise. In California it's
    all done by computer. The smog results are uploaded directly to the
    DMV, using the VIN number is retrieved from the vehicle's computer. I
    believe they do that to prevent fraud. Normally it's very slick. This
    is just an oddball case. I may have to buy another PCM if I can't get
    the proper VIN programmed into this used one.

    carbide, Nov 18, 2006
  4. I would still talk to the smog people, they must have a way to
    override the VIN that is pulled from the vehicles computer.

    Legally I do not think that there is any standing for a government
    agency to use a VIN pulled from a vehicle computer as the
    authoratative VIN. I suspect that buried in some federal law
    is a statement that says that the VIN displayed in the winshield
    is the only legal authoratative VIN. There's certainly federal
    law that requires the VIN to be unique, and for it to be displayed
    in a particular location. It would seem to me that if you have
    a running vehicle that otherwise passes smog, that CA cannot
    legally compel you to make a VIN that is pulled from the vehicle
    computer match the actual VIN assigned to the plate riveted to
    the chassis. After all, not all car computers have VINs in them,
    and I do not believe that OBD-II requires VIN availability as
    one of it's parameters. You could try going here and looking
    into this:

    I think that the VIN inclusion in OBD was for the OBD-III
    standard which is after your 1998 vehicle. I think that CA
    wanted this so they could eventually design a system that when
    the car's emissions systems failed that the car would
    report this to a state agency that could then compel the owner
    to get it fixed immediately. But this scheme raised a huge
    controversy and I think it was abandonded.

    Ted Mittelstaedt, Nov 18, 2006
  5. carbide

    maxpower Guest

    Just take the smog test and be on your way, The only thing they want to know
    is if the engine lite is on and what is coming out the tailpipe. If the PCM
    was not right for the vehicle the lite would turn on and fail.

    Glenn Beasley
    Chrysler Tech
    maxpower, Nov 18, 2006
  6. carbide

    Bill Putney Guest

    In the land of unintended consequences and feel-good laws, they would
    probably require him to scrap the vehicle because the VIN's don't match.
    Just their contribution to "saving Mother Earth". :)

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Nov 18, 2006
  7. carbide

    MT-2500 Guest

    Vin no. can not be reset after it is programed in but.
    But you might check it with a scanner. A used one may not even have had
    it programed into the pcm yet.
    If that is the case you can punch it in with a good scanner.
    Also when you have a scanner on it check and see if the tire size is
    set right.
    That part can be reset.
    The Vin No. in pcm should not be a problem on inspection as long as
    check engine light is not on and no codes set.
    Good Luck
    MT-2500, Nov 18, 2006
  8. carbide

    carbide Guest

    That's encouraging, I guess I can ask. I'm dubious, though, unless the
    smog techs have a way to override the VIN. As I said, it isn't going to
    fly if they try to send the pass data to the state with the wrong VIN
    carbide, Nov 18, 2006
  9. carbide

    carbide Guest

    This is annoying, but I support the smog program. It's really
    necessary in California. Even with these laws, my eyes sting from the
    smog when I visit relatives near Los Angeles.

    So I guess you could say they are literally "feel-good" laws. ;-)
    carbide, Nov 18, 2006
  10. carbide

    Greg Houston Guest

    Are you sure the DMV/inspection station reads the VIN from the car? I
    don't believe there are any generic protocols to permit this, so they
    would need specialized equipment for all makes, which doesn't sound

    Where I live, the emissions inspection station is also online in real
    time to the DMV. The VIN is obtained by scanning the barcode inside the
    driver's door. For some reason the computer always prompts for the
    engine model, even after it already has the VIN (which could be decoded
    for the engine model if they felt like it). The inspection is primarily
    now done via the OBD-II system, in most cases they don't even do a
    dynanometer test for OBD-II cars, which they had been doing earlier.

    My inspection station is friendly so I've been able to watch the process
    pretty carefully.
    Greg Houston, Nov 18, 2006
  11. carbide

    Greg Houston Guest

    I believe you are correct about VIN not being in the OBD-II parameters.
    That level of detail generally requires specialized equipment from a
    dealer (or Snap-On, etc. --very expensive) There is no OBD-III standard
    active. The newer CAN protocol will be required by all vehicles, I
    think by M.Y. 2008. Many cars have been already using it, and started
    as early as 2003.
    Greg Houston, Nov 18, 2006
  12. carbide

    MT-2500 Guest

    Talk to the inspection station and explain the situation.
    And If all else fails.
    A computer rebuilding co. should be able to erase the vin no.
    Or exchange you for another one.
    Check you local area for one.
    I have one in Texas if you need there 800 no or address.
    Post back
    Good Luck
    MT-2500, Nov 18, 2006
  13. carbide

    carbide Guest

    OK, got it smogged so here's the scoop:
    They just scanned the barcode on my registration renewal form which the
    state (California) sent. They got the VIN number off of that form, not
    from the PCM. So the junkyard PCM wasn't an issue, just as some of you
    said. I worried about it for nothing. ;-)

    It passed smog with flying colors, so I'm set. BTW, I paid $65 + $15
    shipping for that used PCM. I found it up in Washington using this

    Thanks for your help, guys.
    carbide, Nov 25, 2006
  14. carbide

    MT-2500 Guest

    You are welcome and.
    Thanks for posting back how it went.
    Glad all went well with no problems.
    I really do not know why they put the vin no. in the pcm anyway.
    It does nothing as far as the pcm goes.:grinyes: :grinno: :lol:
    MT-2500, Nov 25, 2006
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