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Thread: How to communicate with swapped pcm to tune?

  1. #1
    Junior Member FirstGenThree's Avatar
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    Question How to communicate with swapped pcm to tune?

    New to programming, recently purchased FlashscanV2. I have an '03 5.3 that is in my '87 S10. I have the complete engine harness, pcm, and underhood pdc. I have thinned out my harness as per LT1swap.com (mostly stand alone) but am keeping emissions. I also have the donor dash harness with bcm (not installed). However I have cut out the c1 underhood connector to mate my stock chassis harness at the firewall to the 5.3 underhood pdc. I have the DLC wired up in the engine bay currently just to see if everything is online and powering up. I can not communicate with the pcm via FlashscanV2 or a generic scan tool. According to alldata the bcm tells the pcm to turn on when certain criteria are met. I am wondering if I need to wire in the bcm just so I can communicate and turn off the VATS and bcm etc? Is there simply another wire that I need power to in order to turn on the pcm? How do the bench programmers do it? I am willing to make/modify a bench harness if need be but that's essentially what I have isn't it? I will be verifying all my powers/grounds tonight per the wiring diagrams as well as i'll post the hardware/part # for my pcm. Trying to give enough detail but not get too lengthy, thanks in advance. Build thread on www.v8s10.org under the same username. Right now i'm just wanting to get rid of VATS and nuisance codes, no internal engine mods, will tune for CAI and exhaust once its running. Pcms is 12582605 and hardware is 12580786
    Last edited by FirstGenThree; July 16th, 2012 at 01:37 PM. Reason: additional info

  2. #2
    Junior Member FirstGenThree's Avatar
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    Update I tested all of the powers/grounds to the pcm and was missing a 12v source. It seems my pdc may be from a diff year than the harness/pcm because I could not find continuity through the pdc to a fuse for this wire. I will have to re-pin it if there is an available fuse I can dedicate for this.

  3. #3
    Joe (Moderator) joecar's Avatar
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    Hi FirstGen3,

    There is a bench harness tutorial in the Documents folder under EFILive in Program Files...

  4. #4
    Junior Member FirstGenThree's Avatar
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    Hope this will get noticed here, don't wanna start a new thread for such basic info. I have been scouring the threads and tutorials but I just end up reading for hours about diff topics rather than finding answers. So I found the thread on vin licensing and which type of module uses all or part of a license and that makes sense. So if I license my pcm mentioned above, I can later change the VIN in it to that of the project vehilce if I desire? The license stays with that module regardless and it really doesn't matter what VIN is in it..? Guess i'm just looking for confirmation on this or what other people are doing with swaps. I was able to communicate with my pcm last night and will try to dl my current tune so I can start making changes for the swap.

  5. #5
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    VIN license is sort of misleading, it should really be a Controller license (or controllers). A FlashScan V2 or AutoCal VIN license allows you to flash 1 ECM/PCM AND 1 TCM. That means if you flash a single PCM, you should have 1 ECM/PCM and 2 TCM licenses left on your V2/AC. The FlashScan V1 license is for 1 ECM/PCM OR 1 TCM, but not both. When EFILive V7.5 and the FlashScan V1 hardware was released in 2005 (I think), most vehicles were using a single PCM and not the more common ECM/TCM combo GM uses now. So with the invention and release of the FS V2, the license model was changed to better suite the modern GM controllers (and now Cummins).

    And yes, you can put whatever VIN you'd like in the PCM, it doesnt matter.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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    Junior Member FirstGenThree's Avatar
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    So I wont burn a TCM license on this particular vehicle.. sweet. Glad to see its changed back, the thread I found was probably rather old, I don't recall the date on it.
    Well I have viewed the info on my pcm and it is for a vin T 5.3 in a truck and my injector part numbers are for a vin Z FF probably from a tahoe. So it looks like I need to visit tune depot and find a flex fuel tune to start with then modify for swap. Or would it be simpler to reconfigure tune for diff size injectors and go that route? I won't be using a fuel composition sensor nor running on E85 so im not sure what if any other related things would affect the tunes. Opinions welcome keep in mind i am an efilive noob but an experienced technician.
    Thanks for all the replies so far. Also is this appropriate to just run with this thread? and update as I go kind of like a build thread? Unless of course I have an urgent and or totally unrelated question that i'd want to get noticed sooner.

  7. #7
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    It really depends on how your harness is wired. Im guessing it's setup for a truck being a 5.3L. What are your goals for this swap, do you need FI support for a blower later on or is staying N/A?

    If you just want to have it run correctly on a stock 5.3, what is the engine out of? Did the harness come with the engine, or did you buy them separately? Use whatever the engine is physically running, ex: engine is from a Tahoe and the PCM tune is from a Silverado, flash the PCM with a Tahoe OS and then make your modifications (AutoVET, disabled rear O2s if necessary, disable VATs, etc). UNLESS, the harnesses are pinned differently, then stick with the existing tune that matches the harness and adjust the injector settings, VE, spark, etc (copy/paste from a stock Tahoe).

    Hope that helps a little.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  8. #8
    Junior Member FirstGenThree's Avatar
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    The harness was still installed on the engine when I purchased it used, so I'm 98% sure that was never changed or swapped. The engine is an '03 ff 5.3. I did receive a pcm at that time also but I believe he pulled one off a shelf that was marked '03 pickup, so I'm most certain this was not originally paired with the engine I purchased, which coincides with my findings posted above. Was FF offered in a pickup in 03? I believe just tahoes.. if that's true then I should go the tahoe os/tune route. I should/will review connector pinouts for these 2 pcms and look for any differences so I can make changes before taping/looming my harness back up.

    As far as power adders go, that is in the back of my mind. I would love a turbo or procharger on this truck but step one is get it running. Step 2- mild tuning for the cai and custom exhaust it already has. Step 3- If it runs at least a 13.99 in the 1/4 (assuming traction issuses resolved) then I wont do much as far as engine mods. If it's a turd it will get cam and head work, or power adder right quick. Goals are reliable fuel efficient daily that's worth taking to the track. If I can haul two dirt bikes around on the weekends and get 30 highway (yes I know that's high) then i'll be happy, and if i'm no where near 30mpg highway, then i'll be looking for much lower ET's also.

    Thanks for all the input.

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