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Thread: Newbie question regarding Red/Blue PCMs

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  1. #1
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    Newbie question regarding Red/Blue PCMs

    Are the internals (processors, connector plug wiring, etc.) of Red/Blue PCMs the same? I have both a 16168625 BBMX and a 16195925 BHRJ. The 8625 is from a '93 Chevy Sierra 4.3L (I believe) while the 5925 is for a '94 Olds Bravada 4.3L. I have seen a bunch of write-ups on the 8625 and, therefore, my plans are to use the 8625 in my '92 4x4 S-10. On the other hand, I can find nothing about the 5925. I am wondering if the only difference is the chip and not the physical internals.

    I ask this because I am running into the same "no start/run" problem when I install both PCMs. In so doing, I am trying to determine if the issue to the no start/run is the PCM or the adapter that I have constructed as I learn about tuning.

    Lastly, is it possible to turn the 5925 into the equivalent of an 8625 by reprogramming and installing a PROM?

  2. #2
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    I've wondered how much hardware difference there is as well.
    .
    1994 Chevy G30 Van "Big Blue"
    5.7 TBI, Vortec Heads, Summit Intake, Thorley Short Headers with dual 2.5" exhaust, 4L80E transmission

  3. #3
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    One would think that GM would not design separate pieces of hardware to accommodate the various makes, models, and engine/transmission configurations. In the absence of an authoritative/definitive response from someone, and once I get more comfortable with and know what I am doing with these PCMs, I will perform a test to validate or invalidate my hypothesis regarding common PCM hardware.

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    To somewhat answer your question, they are different beasts in a few ways. First the 8625 will run the TBI engine just fine, with 2 injectors, blah blah blah. The 5925 is meant to run the CPFI(spider injector) style of multi-port injection. Is the wiring at the red/blue connectors different between the two, you betcha! Stick to the pcm that "came with" the engine you are trying to run. The 5925 likely will never start your engine in its current state.. HTH

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

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    buddrow, thanks for providing input to this thread. So, based on what you are saying, the 5925's red/blue connectors will NOT fire the 2 TBI injectors because the BCC (which includes the .bin, .xdf, and . adx are different plus the red/blue connectors are wired differently. Interesting...

    With regard to your recommendation of sticking with the PCM my engine came with, all my research/readings online say that it is possible and likely worth the effort to upgrade to the 50x's faster 8625 PCM rather than stick with the slower 4288 ECM that came stock in my '92 4.3L S10.

  6. #6
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    It's not so much the connectors themselves as the hardware internal to the pcm as well as the software that runs everything is different.

    The '4288 is a direct replacement for the '7747, provided they are both from the same engine size, 4.3,5.0,5.7... The '7747 may not be the best choice for performance applications, but for simplicity, it would be an easier swap than the 8625 since it's a direct swap, no pin swapping. I know this because I have done such a swap in a friends '92 with the '288. The 8625 will run the 4.3L, you will just have to do some pin swapping at the pcm connector. There are wiring diagrams available on this site, or if necessary I may be able to provide you with wiring diagrams for both pcms.

    The BCC(broadcast code) is the calibration code name/designation.
    the .bin is the actual calibration file
    the. xdf is used by tunerpro to organize the .bin file for human viewing, modification, etc.
    the .adx is solely for datastream interfacing, datalogging, etc.

    These are all different from one pcm to the next, but are the same between different calibrations/.bins of the same pcm number, if that makes sense.
    Just food for thought.

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

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