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lets talk ECM and PROM chips ....."any guru's here? Im lost"

Discussion in 'The Garage' started by uglychevyZZ4, Oct 19, 2003.

  1. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    lets talk ECM and PROM chips .....\"any guru\'s here? Im lost\"

    /forums/images/graemlins/confused.gif I have had my ECM diagnosed 2x as being bad, replaced it (warranty) 3x and still same issue, so how do I know if its the prom chips? wtf do the prom chips do anyways?
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    What kind of symptoms or problems are you having? The chip basically has fuel and timing curves burnt into it.
     
  3. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    cuts off, or dont run good intermittent. if i disconnect the battery and reset the ecm, then drive it, its great. after like 1 day, goes to hell.im just curious if they keep misdiagnosing the ecm instead of the prom chips?????????
     
  4. Thunder

    Thunder 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    PROM= Programable read only memory. Its the brain of the ECM.
    As the above post says it has all the engine runing dats burned into it. And it reacts to changing operating conditions and tells the ECM what to do.
    The ECM acts like a big switch It sends all the right voltages to the right engine controls and feeds the PROM chip operating data. It has a basic program programed into its hard memory that can run your engine if the PROM fails or there is loss of sensor input. Its the "limp home" mode people talk about.When in linp home Sometimes it will show no trouble codes unless the ECM is reset by disconnecting power. Then scanning again.
    I have seen shops mis diagnose a sensor problem as a faulty ECM. Something as simple as a bad O2 sensor. Can put the ECM in limp home mode(bypass). Someone who doesn't know what they are doing will scan it and see all the data is not right and not changing like it should and think the ECM is bad. When in reality it is running on the program stored in its hard memory where no values are not changed.
    All the sensors should be checked to see they are operating right before replacing the ECM.

    Are you geting any trouble codes? If your PROM is bad it should throw a code 51.
    Does the check engine light come on when the key is turned on but the engine not started?
    If your CEL doesn't come on AND the bulb is not burnt out.
    Or you get a code 55 its usually the ECM.

    If you are blowing ECMs there is usually a short somewhere in the system. There are Clear instructions that come with every ECM on how to test for these problems.
     
  5. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    EVERY sensor is new,
    TBI is rebuilt now,
    ecm x3 is new,
    distributor COMPLETE is new
    injector harness new
    map sensor harness new

    intermittent:--->
    -rpm at idle
    -everything will shut off for split seconds at a time, like a switch.. intermittently also.

    only thing NOT new
    egr
    egr vac.control
    esc
    fuel pump
    /forums/images/graemlins/angryfire.gif
     
  6. mudjunkie 82

    mudjunkie 82 1 ton status GMOTM Winner

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    my Girlfreinds van was doing the same thing,Turns out the EGR valve was sticking,would idle real rough then would be ok,Then bad again
     
  7. Batmanjr

    Batmanjr 1/2 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    Mine was just doing this as well.... It turned out to be really bad dryrotted vacum lines! Sounds like you have a vacum leak possibly! /forums/images/graemlins/thumb.gif
     
  8. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    all new vacume line kit from GM /forums/images/graemlins/frown.gif can a egr just make it turn off then back on though /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif I was a mastertech for 12 years and this one has me stumped . so does a prom GO bad?
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    [ QUOTE ]
    all new vacume line kit from GM /forums/images/graemlins/frown.gif can a egr just make it turn off then back on though /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif I was a mastertech for 12 years and this one has me stumped . so does a prom GO bad?

    [/ QUOTE ]

    EGR's can get carboned up and stick OPEN. The weird part is the resetting makes the problem go away. Might just be a coincedence and actually be the EGR. If it's stuck open it will die at idle. Unplug the EGR vacuum line and see how it does. It WILL throw a code but otherwise should run fine.

    How are your grounds? Bad body ground may case a low volt issue to the ECM and whack it out. I could see resetting it causing it to work till the ground fails again. Check the ground strap off the passengerside head to the fire wall.

    Bad diodes in the Alternator can also play hell with the ECM and sensors.
     
  10. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    /forums/images/graemlins/shocked.gifHrmmmmm, that strap was off, thats prolly the one thing Goober made me do during the engine swap. /forums/images/graemlins/rotfl.gifNOT /forums/images/graemlins/rotfl.gif Ill bolt it up and see...thnx grimmy /forums/images/graemlins/thumb.gif
     
  11. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    [ QUOTE ]
    /forums/images/graemlins/shocked.gifHrmmmmm, that strap was off, thats prolly the one thing Goober made me do during the engine swap. /forums/images/graemlins/rotfl.gifNOT /forums/images/graemlins/rotfl.gif Ill bolt it up and see...thnx grimmy /forums/images/graemlins/thumb.gif

    [/ QUOTE ]

    Master Tech huh /forums/images/graemlins/thinking.gif Of what, bicycles /forums/images/graemlins/rotfl.gif j/k buddy /forums/images/graemlins/wink.gif
     
  12. reeser

    reeser 1/2 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    next thing to check is the fuel pump. mine went bad and made the ecm read bad and the esc. i ended up replacing the ecm, prom chip, esc and the fuel pump all because of the faulty fuel pump. /forums/images/graemlins/thumb.gif
     
  13. K5 NUTT

    K5 NUTT 1/2 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    ecm/prom failure is a 5 percent thing...very rare.

    proms have glitches..and thats why gm did rolling chip reburns with diff pn#'s..sometimes 40 a year...

    i'd start with the basics...fuel psi...vacum reading...ground strap to frame = 0.3 ohm...ign/ batt volts to ecu...etc...before we go swapping ecm's...


    dw
     
  14. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    I only swapped it because i was told after a scope reading that the injector drivers were bad, well, that was BS /forums/images/graemlins/angryfire.gif
     
  15. ntaj*ep

    ntaj*ep 1/2 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    Do GMs use a main relay that supplies power to the ECM and Fuel system?
    I would do a full input test at the ECM and each sensor until you find the problem. Those systems seem pretty ancent compared to the systems nowadays. /forums/images/graemlins/thumb.gif
     
  16. K5 NUTT

    K5 NUTT 1/2 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    tbi injectors rarely go bad...you can watch there operation with a timing light to make sure they are spraying a good pattern. The gm driveability book teaches us to find out what caused a quad driver to burn out...ie: relay contacts...short to ground...excessive resistance in a circuit...etc. Which any of these depending on how bad will cause a quad driver to fail. My tbi'd 79 K5 has had a slight glitch since day one about 3 years ago...it has a slight idle burp (50-100 rpm) in drive foot on the brake...and it doesn't do this all the time. Since i am off work for a bit...tomorrow i'm gonna call them on it and see what we can do..the chalet got tbi'd on my own...built my own harness etc...i'll see if i can find the page in the riveability book that defines how to check the quad drivers.

    DW
     
  17. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    Thnx /forums/images/graemlins/thumb.gif Hey Aaron, you have a F/P testing kit thatll hook up inline around my filter? mine only has hose clamps and wont work /forums/images/graemlins/frown.gif
     
  18. ntaj*ep

    ntaj*ep 1/2 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    I have the Honda kit /forums/images/graemlins/rotfl.gif
     
  19. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Re: lets talk ECM and PROM chips .....who knows what the prom does?

    /forums/images/graemlins/smirk.gif
     
  20. FWP

    FWP CRS

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    Re: lets talk ECM and PROM chips .....\"any guru\'s here? Im lost\"

    I'm not a guru by any means, but here's my .02.

    Listen to what DW (K5NUTT) has to say, he's probably been there /forums/images/graemlins/wink.gif

    If you have access to a laptop with a serial port, Build yourself a WinALDL cable and get some info right from the ECM. Your troubleshooting will be alot easier, and you can post up what kind of info you get.
     

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