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Thread: 16197429 Documentation Project

  1. #1
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    16197429 Documentation Project

    the 7429 is the PCM from the 93-95 northstar cars, while it's in my posession, i'm going to try and document as much of the hardware as possible.

    these are P66 PCMs with both 68HC11F1s on a single board. two 27C512 PROMs in a single MEMCAL with a modified P4 knock filter.

    3 32 pin connectors, of which only 6 pins aren't used in some form in any factory application. these things are LOADED with hardware, a total of 41 ICs, most of which i can't identify yet.

    interesting stuff found so far: there are 8 FETs used that drive the injectors, there is another identical FET right by them so i was curious to see what it does. it's output runs through a large 1 ohm, 1% resistor and goes on to power the pressure control solenoid in the 4T80E. marked as a 9395, most likely an IRF9395.

    i'll probably have some pics up tomorrow.
    Attached Files Attached Files
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  2. #2
    Quote Originally Posted by RobertISaar View Post
    the 7429 is the PCM from the 93-95 northstar cars, while it's in my posession, i'm going to try and document as much of the hardware as possible.

    these are P66 PCMs with both 68HC11F1s on a single board. two 27C512 PROMs in a single MEMCAL with a modified P4 knock filter.

    3 32 pin connectors, of which only 6 pins aren't used in some form in any factory application. these things are LOADED with hardware, a total of 41 ICs, most of which i can't identify yet.

    interesting stuff found so far: there are 8 FETs used that drive the injectors, there is another identical FET right by them so i was curious to see what it does. it's output runs through a large 1 ohm, 1% resistor and goes on to power the pressure control solenoid in the 4T80E. marked as a 9395, most likely an IRF9395.

    i'll probably have some pics up tomorrow.
    Cool! Good luck, man.

    I have a Northstar Fiero and was using that computer for a while. I took some reasonably high res shots of the board... Not that it's a lot of work, but I could probably dig them up for you.
    There's certainly a lot of stuff in the unit. The board is at least 5 layers.

    I also have a dyno-only calibration that was snuck out of GM. It ran the engine without automatic (my swap is a stickshift) fairly well. Only problems were stall when sinking the clutch from overrun and running just a little bit rich. The BLM's were disabled, too.

  3. #3
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    i took a few shots using the wife's T3(12.2MP DSLR) that way i could start labeling stuff as i discovered it's usage. i do need to take more though, especially at least one on the backside. there are a lot of tiny SMT resistors on the back.

    i don't think i'll be able to get this down to the Ludis level of completion, but it will be more than what is known about it already.

    that calibration..... happen to know if it was built off of the 93, 94 or 95 codebase? IIRC, they were all slightly different compared to each other.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    in my search for info:

    http://www.retro.co.za/efi/DIY_EFI/1999/efi4-206.txt

    found that the 94-95 LT1 PCM uses some common ICs as well. i've determined that the 129170 chip seems to be the injector controller, the LT1 uses it as well. based on the date code, i'm assumg it's first application were the cadillac V8s that ran SFI.

    the LT1 also uses a crystal that causes the processors to run at 3.15MHz instead of the normal 2.1MHz that the P4s and this P66 unit does.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    RIP EagleMark's Avatar
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    Quote Originally Posted by RobertISaar View Post
    two 27C512 PROMs in a single MEMCAL with a modified P4 knock filter.
    Don't think I've ever seen that Memcal. Are you thinking this PCM is a cure for I/O and space room your having with nAsty1?

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    it is one of the potential candidates.

    and the MEMCAL certainly is unique... technically, the two missing pins on the knock filter aren't supposed to do anything. and the two on the far left don't either, they're for support, just like the P4 filter. the important 4 pins are on the right.

    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    i had forgotten how nice it was to work with a part that has nice documentation from it's creator... the pink book is an absolute goldmine of info for any P6/P66 application.

    A/D channels on E and T side

    E-side
    ch0 = MAP
    ch1 = TPS
    ch2 = none?
    ch3 = ignition voltage
    ch4 = right/rear O2 sensor
    ch5 = left/front O2 sensor
    ch6 = trans temp
    ch7 = EGR position

    T-side
    ch0 = PCS measure
    ch1 = cruise servo position
    ch2 = power steering pressure switch(read as a sensor?)
    ch3 = coolant temp
    ch4 = ignition voltage
    ch5 = MAP
    ch6 = ???
    ch7 = TPS

    T-side channel 6 is used for something, but i haven't traced the circuit yet to find out what. E-side channel 2 doesn't ever appear to be read?

    EDIT: there may be more.... i don't see IAT in that group.
    Last edited by RobertISaar; 08-26-2013 at 12:11 AM.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    RIP EagleMark's Avatar
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    That Memcal is cool looking. But no netres?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    correct. i don't know if there is a limp-home function at all on this PCM, haven't gotten that deep into it yet.

    also, one of the chips on-board was used in P4s for a mux'd a/d channel, i get the feeling it is used that way here as well.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  10. #10
    Quote Originally Posted by RobertISaar View Post
    that calibration..... happen to know if it was built off of the 93, 94 or 95 codebase? IIRC, they were all slightly different compared to each other.
    No idea... The .bins were on the DIY-EFI FTP site as of several years ago. I still have them as well, but would probably take me some time to dig them up.

  11. #11
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    hmm..... weird. happen to remember a filename?
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  12. #12
    Would have had "Northstar" and "A" in one filename and "Northstar" and "B" in the other... might also search for variants of 16197429.

  13. #13
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    hmm..... there are a couple of northstar A and B BINs in the gearhead-efi archive, but i already have both of them and a few more.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  14. #14
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    discovered that the pink book doesn't necessarily even mention certain aspects that are relevant in the F1.

    found a supplimental addition for it.

    http://cache.freescale.com/files/mic...=Documentation

    explains locations if not specific functions.... should make certain things easier to play with.



    and i've come to a conclusion about the 6811 family: they kind of need all of those extra, custom-made chips for anything beyond basic functionality. for example, to operate SFI on an 8 cylinder engine using only the processor, the "simplest" way would be to use 16 TOC channels. 2 channels per injector would be needed because you would need to set up "time until turn injector on" and "time until turn injector off". and..... there are not 16 TOC channels to use, there are 5, at most. so what GM did was have some custom-made chips built that essentially replicated at least part of those functions. with the P4, nearly everything is external to the actual processor. with the P6, some of it moved onboard, but a lot of the complicated functions are still "outsourced" to the other chips on the board.

    i can't think of a way to perform SFI on that many cylinders without a whole bunch of non-existant TOCs to do the work. i guess GM ran into the same problem, so they had something made up that is basically a programmable timer that sniffs on the address and data bus to see when it is being written to. so now instead of eating up TOC channels that didn't exist, you just deal with it all over the existing address and data bus.

    there is such incredible complexity behind all of this. when GM went OBD2 and largely used the 68332, even more of the functions made it onboard via the TPU. this is why they can do stuff like SFI and coil-per-cylinder ignitions with relative simplicity. it all stays within a single IC until it needs to turn on an injector or coil driver and does it directly. its too bad you have to have an octo-core brain to easily follow along that assembly.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  15. #15
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    Interesting. So is this to simply make a XDF/be able to tune the northstar, or to be able to use this ecm as a OBD1 SFI/DIS ecm for conversions?
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

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