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Thread: Bench programming a LT1 PCM ?

  1. #1
    EFI GearHead ! EagleMark's Avatar
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    Bench programming a LT1 PCM ?

    This is a winter project, any day now up north here?

    Does any have information or links to Re-Flashing an LT1 PCM on the bench? I have bench.

    I've done it in my car with WinFlash. Made adjustments to Bin in TunerPro. Reflashed through ALDL port.
    Got a couple spares in case I brick one, also check charging system on car, batterey voltage car off, load test and if all is well I leave a small batterey tender on the batterey. Instructions say no chargers but this is a tiny charge to keep topped off on like a harley in storage. That what I bought it for 15 years ago. I also start reading and flasing with full charged laptop batterey. No charger! Done mine 5 times now with no issues!

    Would it be as simple as running ALDL lines and power lines to the PCM? Probably be nice to get some PCM pigtails, but so few wires and I think you only use 2 plugs? I have wiring diagrams for all if I have not added them to the library.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Super Moderator dave w's Avatar
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    Re: Bench programming a LT1 PCM ?

    I'm sure the LT1 PCM can be bench flashed, similar to the way I bench flash the LS1 PCM. Using the LT1 PCM schematic you will need to figure out what are data pins, ground, power (battery / ignition on) pins.

    dave w
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    EFI GearHead ! EagleMark's Avatar
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    Re: Bench programming a LT1 PCM ?

    Just doesn't look like a lot of wiring to do!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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    Fuel Injected! JeepsAndGuns's Avatar
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    Re: Bench programming a LT1 PCM ?

    I am still new to all of this and have lots left to learn, so forgive the noob question. But if all the flashing is done through the adld plug, whats the need/reason to remove the pcm from the car just to re flash it? Or is there a limit to what can be flashed with it in the car, and it need to be removed and plugged into something special to do a diffrent/more in depth re flash?
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    EFI GearHead ! EagleMark's Avatar
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    Re: Bench programming a LT1 PCM ?

    If the LT1 and LS1 (and anything OBDII) are not done properly they turn into bricks! Having a security alarm go off during a flash can cause a brick! Garage door openers can cause them to become bricks... there are some tricks that work to restore them some not! My auto level DynaRide suspension came on during a reflash and I nearly flipped!!! Now I pull that fuse! If I had a low batterey or not running the tender on a known tested fully charged car batterey that could have bricked it!

    On the bench I run off a car battery that runs a tender (like in my LT1 thread) and have 2 battereys for my laptop. I always read and flash on fresh full charge, no charger. This keeps the narrow reflash voltages in check. Even if my electric power goes out during a reflash on my bench I have no loss!

    You can also flash one for someone who needs many things changed before start up. Or may need adjustments for cam. Makes it way easier. I like doing conversions from stock harness to easy hook up on conversion motor, then adjust chip as needed for EGR or no EGR etc... then I run them on my bench and know they will run on the car. And always have! Long winters in Idaho so I get it all done on bench in a nice warm shop.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Fuel Injected! JeepsAndGuns's Avatar
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    Re: Bench programming a LT1 PCM ?

    So basicly they are very sensative? Or only when flashing?
    So there is a narrow voltage range that has to be maintained when flashing, and if something else comes on or goes off that could cause the voltage to change, it fries the computer? If thats true I had no idea those were so sensative. I can see the reason for concern.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    EFI GearHead ! EagleMark's Avatar
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    Re: Bench programming a LT1 PCM ?

    No they are very robust PCM!

    Only during the reflash everything has to be right.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  8. #8
    Electronic Ignition!
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    The LT1 PCM's don't have Boot Block Flash, so if something happens during flashing, it has nothing to boot on to recover, so the boot loader and the flash are gone, hence it hangs up in a pretty goofy state.

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    Newbie question. With the possibility of bricking the LT1 PCM, is there much of a benefit of using it over a MEMCAL based PCM?

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    Fuel Injected! roughneck427's Avatar
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    I made one using the blue and black connectors. The serial data wire for obd1 and ob2 are different I just pull the wire and swap it when needed

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    i don't care much either way for flash vs MEMCAL.... takes less time to swap out a MEMCAL than to wait for the flash to program over the ALDL port.

    the advantage of the PCM itself though, if you wanted the ultimate 6811 based PCM, these are on the very short list of potential winners. all of the dual 6811 units i know of:

    93-95 northstar (dual 64KB BINs in a MEMCAL)
    93-95 3100/3.4 RWD (dual 32KB BINs in flash)
    94-95 LT1 (dual 64KB BINs in flash)
    96-99 northstar (dual 96KB BINs in flash, IIRC)
    96-97 LT1 (dual 96KB BINs in flash, IIRC)

    i THINK those are all of them.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    How long does a flash through the ALDL take?

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    EFI GearHead ! EagleMark's Avatar
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    Exactly? But not that long, just a couple minutes?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  14. #14
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    i can only speak for the 93-95 3100 PCM using the madtuner package, but i seem to remember it taking ~30 seconds to setup and secure comms, then 60 seconds to flash each PROM.

    i imagine 94-95 LT1 will be double that.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Fuel Injected! EDZIP's Avatar
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    Mark


    Old thread...new related questions: I finally located the blue and black connectors and set up the pins via the CATS Off Board Programming Diagram LT1 you supplied. I also looked at your programming bench picture and noticed that the PCM on your bench had a four (4) connectors plugged in. Just want to verify as I finish this LT1 bench flash harness that only the blue/black connectors are required?

    Ed

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