Un-brick a PCM - Chevy Impala SS Forum
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post #1 of 18 (permalink) Old 04-25-2019, 09:12 AM Thread Starter
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Un-brick a PCM

Anybody have a good source to recover a PCM that failed programming? Iím up and running with a used PCM that flashed fine, but would like to get my original going as a spare.
Of course if cost is high for recovery I might just be better off to get another used one for a spare. Snagged this one for $25.
Thanks,

James Paley

-95 Caprice Wagon, 93K, 2.56 gears, No-Slip Locker, Sonnax Line Pressure Booster, 2nd and 4th super hold servos, MSD Cap/Rotor, Jacobs high voltage coil, Global West front springs (760lb/in) with Koni Special D front shocks.
Impala SS rim refinishing in progress, 1.6 ultra pro mags and Bullet vs2700 springs waiting for install

-2011 Caprice 9C3
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post #2 of 18 (permalink) Old 04-25-2019, 10:10 AM
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How did it fail? EEHACK recovered one I thought was dead.
If flash chips need to be removed and manually reflashed cost to have business do it cost will be higher than just buying another.

Give Eehack a try, if it doesn't work I'm sure I could do it if you pay shipping.
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post #3 of 18 (permalink) Old 04-25-2019, 12:04 PM Thread Starter
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Quote:
Originally Posted by babywag
How did it fail?
I was making a change to a speedometer scalar and some TCC release points. I did check stability before starting the flash - I almost always do. It was flashing the T-side only and got almost all of the way through before it failed. I got the message indicating that power needed to be removed from the PCM. I disconnected the battery for a minute or so and was never able to connect again.

Quote:
Originally Posted by babywag
EEHACK recovered one I thought was dead.
I was using EEHACK. I've never had a problem before. I think I may have used a different USB port this time.

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Originally Posted by babywag
Give Eehack a try, if it doesn't work I'm sure I could do it if you pay shipping.
EEHACK is currently unable to connect to this one. If you have some tips, I'll give them a try. Heck, I might be looking right at the solution and not seeing it.

I'm happy to ship it out to you if you are interested in giving it a try. Financially it probably isn't worth putting much effort into it when they pop up cheap now and then... but I'm just the type to spend more fixing something instead of throwing it out.

James Paley

-95 Caprice Wagon, 93K, 2.56 gears, No-Slip Locker, Sonnax Line Pressure Booster, 2nd and 4th super hold servos, MSD Cap/Rotor, Jacobs high voltage coil, Global West front springs (760lb/in) with Koni Special D front shocks.
Impala SS rim refinishing in progress, 1.6 ultra pro mags and Bullet vs2700 springs waiting for install

-2011 Caprice 9C3
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post #4 of 18 (permalink) Old 04-25-2019, 02:01 PM
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The "dead" one I had, using a bench harness to flash it worked for whatever reason.
Same usb adapter, same laptop, in car it was like yours no connection.

I have a chip programmer and socket for the 2 flash chips.
I've fixed 3 out of 4, 4th one was really dead.
Not terrible to unsolder/resolder them if you're handy.
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post #5 of 18 (permalink) Old 04-25-2019, 07:57 PM Thread Starter
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Interesting. If there is a chance it will work with a bench setup, then Iíll give that a try first. There are at least 6 donor caprices at a yard I drive by every day, so getting the harness connectors should be easy.
Seems like it would be nice to have a ďprogrammingĒ harness around anyway.
Thanks for sharing your experience!
Iíll report back with my results.

James Paley

-95 Caprice Wagon, 93K, 2.56 gears, No-Slip Locker, Sonnax Line Pressure Booster, 2nd and 4th super hold servos, MSD Cap/Rotor, Jacobs high voltage coil, Global West front springs (760lb/in) with Koni Special D front shocks.
Impala SS rim refinishing in progress, 1.6 ultra pro mags and Bullet vs2700 springs waiting for install

-2011 Caprice 9C3
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post #6 of 18 (permalink) Old 04-26-2019, 09:55 AM
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Just a FYI,
Some great pages for building bench top programmers:

Bench interface for LT1 PCM

Gerry Massies Home Page

I am building the harness with two ends, one for OBD1 and one for OBD2 for the LT1.

OBD1 connector:
https://www.ebay.com/itm/25194309737...&s=ci&mail=sys

OBD2 connector:
Mouser:
Read the gearhead-efi page.

I plan to use an old ATX computer power supply as the power source for my bench top setup.

Later,
Michael
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post #7 of 18 (permalink) Old 04-26-2019, 10:28 AM
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You might want to use a transformer type power supply. The PCM is not designed to filter the switching noise of a ATX. I think people have used them, For best results and safety issues I would avoid switching power supplies for bench top programming a PCM


Quote:
I am building the harness with two ends, one for OBD1 and one for OBD2 for the LT1.
I would recommend making separate units as one slip will smoke the OBDII.
Quote:
If you don't switch this one line, you'll SMOKE the OBD-2 PCMs. Andrew says he's not sure why, but trust him.... he's done a LOT of these puppies. Gerry

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post #8 of 18 (permalink) Old 04-26-2019, 11:14 AM
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A simple plugin 12v power supply has served me well for years w/o issue.
Needs to be 1amp or little higher.
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post #9 of 18 (permalink) Old 04-26-2019, 02:51 PM
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ATX noise, did not know anything about that.
I ,possibly wrongly, ASSumed a power supply for a computer was clean enough for,,,,, a ,,,,, car computer.

Now that being said, I also have a small gel cell battery in parallel , because with my luck, the power in the neighborhood would go out while programming

Although, I did the all 4 plug deal with mine 15 some odd years back, I think you only need two .
blue and black, I think?


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post #10 of 18 (permalink) Old 04-26-2019, 10:03 PM
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Quote:
ATX noise, did not know anything about that.
I ,possibly wrongly, ASSumed a power supply for a computer was clean enough for,,,,, a ,,,,, car computer. Now that being said, I also have a small gel cell battery in parallel
The gel cell would smooth things out. The same way a car battery dampens the ripple voltage from the alternator.


Put a oscilloscope on a ATX power supply that is powering a 1 amp load. You will find noise and ripple current on most. As 1 Amp is not much of a load for a ATX you may also find the voltage is higher. Not all supplies are well made. Some also need a 5 volt load for good 12 volt regulation.


The 5 volt was used for the computer. The 12 volt was used for the motors on the drives and other non computer stuff.

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