Can I replace my PCM with a Junkyard PCM - S-10 Forum
 
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post #1 of 16 Old 12-07-2009, 04:23 PM Thread Starter
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Can I replace my PCM with a Junkyard PCM

I just got my 96 4.3 2wd back from the dealer and they said my PCM was bad and and it would cost me 300ish for a refurb or 600ish for a new OEM computer I said "that's ok I can do it" and they proceeded to tell me that I could not change the computer my self because it has to be programmed by a dealer is this true? I was just planning on throwing a junkyard PCM into it.

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post #2 of 16 Old 12-07-2009, 04:36 PM
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Re: Can I replace my PCM with a Junkyard PCM

send yours in as a core and get a new one from pcmforless or wait4me
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post #3 of 16 Old 12-07-2009, 04:41 PM
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Re: Can I replace my PCM with a Junkyard PCM

agree. I sent my boneyard PCM to a forum member and he re-flashed it for me, changed it to my rear tires size to correct the speedo for a very nominal amount.

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post #4 of 16 Old 12-07-2009, 04:43 PM
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Re: Can I replace my PCM with a Junkyard PCM

the new one would have to be reflashed with your Vin code before it would work in your truck.
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post #5 of 16 Old 12-07-2009, 05:36 PM
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Re: Can I replace my PCM with a Junkyard PCM

questions...i have a 1998 sonoma and i need to know if the pcm and ecm are the same thing or seperate units in s10s.

I am having a transmission problem and i am thinking it is the computer as it was just completely rebuilt and dont know if the tranny has a seperate computer or all in one.

Also to test this computer theory could i swap one from a 1996 that is identical other than the 1996 has cruise control.

As far as flashing it what do you need to do that? also not trying to hijack thread just saw similar interests being discussed. thanks guys
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post #6 of 16 Old 12-07-2009, 05:46 PM
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Re: Can I replace my PCM with a Junkyard PCM

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Originally Posted by tallymx312 View Post
questions...i have a 1998 sonoma and i need to know if the pcm and ecm are the same thing or seperate units in s10s.

I am having a transmission problem and i am thinking it is the computer as it was just completely rebuilt and dont know if the tranny has a seperate computer or all in one.

Also to test this computer theory could i swap one from a 1996 that is identical other than the 1996 has cruise control.

As far as flashing it what do you need to do that? also not trying to hijack thread just saw similar interests being discussed. thanks guys
the tranny is controlled by the speedo sender fluid.

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post #7 of 16 Old 12-07-2009, 05:54 PM Thread Starter
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Re: Can I replace my PCM with a Junkyard PCM

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Originally Posted by 98layinframe View Post
the new one would have to be reflashed with your Vin code before it would work in your truck.

What will happen if you put the junkyard computer in without having it reflashed?

I am curious because I had some issues with the "bad" PCM and i put in the junkyard PCM and I still have the exact same issues
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post #8 of 16 Old 12-07-2009, 08:18 PM
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Re: Can I replace my PCM with a Junkyard PCM

Quote:
Originally Posted by tallymx312 View Post
questions...i have a 1998 sonoma and i need to know if the pcm and ecm are the same thing or seperate units in s10s.

I am having a transmission problem and i am thinking it is the computer as it was just completely rebuilt and dont know if the tranny has a seperate computer or all in one.

Also to test this computer theory could i swap one from a 1996 that is identical other than the 1996 has cruise control.

As far as flashing it what do you need to do that? also not trying to hijack thread just saw similar interests being discussed. thanks guys
The PCM that I have in my 01 sonoma 4.3 2wd Auto is from an 01 blazer 4.3 2wd Auto, granted I'm not sure if that would have mattered, but I wanted to take no chances. I put the PCM in when I got it before I had it flashed, truck will have full lights etc and junk, but when you try to start it, it will just crank. There is no work around, it has to be done.


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Originally Posted by NYG Eric View Post
What will happen if you put the junkyard computer in without having it reflashed?

I am curious because I had some issues with the "bad" PCM and i put in the junkyard PCM and I still have the exact same issues
If you have a problem with your stock PCM, and then you have a junkyard PCM flashed, and you still have the same issue, you have a different problem altogether.

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post #9 of 16 Old 12-07-2009, 08:43 PM Thread Starter
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Re: Can I replace my PCM with a Junkyard PCM

Hmmm very strange. My issue is I am missing first and fourth gear. I took my truck the dealer to have it diagnosed and they said my PCM was bad. I stopped and picked up a used one on the way home put it in and I am having the exact same problem. However the truck did start and did not she the symtoms of the diffrent PCM above. Any thoughts I have already dumped much more in getting this issue fixed than I should have.

Cleaned plugs between PCM and Tranny - No Change
replaced shift solenoids - No Change
swapped Transmissions -No Change
Swapped PCMs - No Change


I am running out of options unless the unmatched PCM is in "limp mode" which gives me the same symtoms but that does not seem to be the case for a junkyard computer
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post #10 of 16 Old 12-07-2009, 11:07 PM
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Re: Can I replace my PCM with a Junkyard PCM

I personally have done this. Changed out a defective ECM/PCM with one from a salvage yard. Only thing to remember is that the part numbers on sticker should match.

(Example:
Part Number: 77-3993
Notes: R & R item only O.E.M. #16163993
Part Number: 77-9278
Notes: R & R item only O.E.M. #16159278
)

Just remember.., u get what u pay for nowadays and that alot of salvage yards wont take any electronics back or refund yur $$$ once bought.

Best way..., find a used one..(with matchine numbers), try it out to see if it works for you..., if not.., get it reflashed by a tech or someone with the equipment to do it.
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post #11 of 16 Old 12-30-2009, 04:31 AM
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Re: Can I replace my PCM with a Junkyard PCM

Sorry I'm a little late on this topic, but a few weeks back I had a PCM go bad. I fried it when I tested the fuel pump by jumping the relay--only I got the pins backwards and jumped the PCM instead of the pump. As ridiculous as it sounds, I'm smarter than that. Usually.

Anyway, the truck ('98 Jimmy) would still start and run but only after the oil pressure switch closed. And the transmission shifted wicked-hard; it barked tires between gears. And the Check Engine light kept coming on with an EGR code. I burnt a lot of the PCM, needless to say.

So I went to the junkyard and bought a used PCM (same numbers) out of a Blazer and put it in mine, hoping to drive off with it. No chance. The engine would start but then shut right off. It wouldn't run for more than two seconds.

I took it all to the dealer and paid $84, and haven't had a problem for 2,000 miles now. Shifts fine, fuel pump primes, engine light is off, it's all good.

The short answer in my experience is: no, you can not plug a junkyard PCM in without flashing it to your VIN. Don't sue me, it just my opinion.
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post #12 of 16 Old 12-30-2009, 09:48 AM
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Re: Can I replace my PCM with a Junkyard PCM

Well just to chime in also, my truck is a 98 4 banger manual transmission. I have been having issues with my truck and have been throwing tons of parts at my truck in an attepmt to solve the problem. At one point I even replaced my PCM with a junk yard unit... that's it.

I pulled the old one plugged in the new one and went on my merry way, it didn't solve my problem but it didn't cause any either. I have been driving with the Junkyard PCM in my truck for over a year and my original one is still sitting in my garage. I didn't see any reason to swap it back out since the new one made absolutely no difference in the truck at all (for better or worse).

I think it has to do with the fact the newer trucks have the chipped keys that talk to the PCM and that is why they have to be programed. Fortunately my truck does not have a chipped key... hell my ignition switch is so worn out I can pull the key out without turning off the truck, which comes in helpful for warming it up in the mornings or turning the passenger airbag on/off while I am driving.

Long story short in some trucks you can definately swap them straight out, I know because I have done it. While I am also sure that in some trucks you can not. The only thing I know is the one I pulled was from practically a mirror image of my truck 98 reg cab, short bed, 4 cyl 5 spd, Ac, no power accessories, everything but the color was the same, right down to the rear end gear ratio.

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post #13 of 16 Old 12-30-2009, 09:58 AM
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Re: Can I replace my PCM with a Junkyard PCM

steal one from the junk yard and see.

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post #14 of 16 Old 01-03-2010, 12:38 AM
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Re: Can I replace my PCM with a Junkyard PCM

and then cover it in bondo and screw it down with dry wall screws right?
around here the junkyards dont charge hardly anything...why steal?

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post #15 of 16 Old 01-03-2010, 05:01 PM
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Re: Can I replace my PCM with a Junkyard PCM

In a first gen with OBD1 you can open it up and swap the chip into a new PCM and install it. In a second gen with OBD2 it has to be re-flashed by the dealer or someone with the right computer.

94 1st-gen Blazer 4.3L 4x4
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post #16 of 16 Old 06-29-2016, 07:43 AM
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Re: Can I replace my PCM with a Junkyard PCM

On early OBDII PCM's you can swap out the PCM and the truck will fire up and run, sometimes with everything working properly. Other times (depends on PCM version) you're stuck in "limp mode" which only gives you engine management basics and 3rd gear. You still need to flash the replacement PCM, which will correct speedo errors and other system problems, related to installed options (correct gear ratios, etc.) and mileage/environmental adjustments the PCM makes in real time.
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