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Thread: E-Cell Program Modifier

  1. #1
    Electronic Ignition!
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    E-Cell Program Modifier

    Just getting to know all the sensors and actuators connected to the ECM on my '83 Trans-Am (LU5 crossfire) and I find a small module which the Service Manual identifies as "E-Cell Program Modifier". Anyone know what is the function of this module or what is the nature of the signal it sends to the ECM and under what circumstances ?

    Thanks.

  2. #2
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    Lol...

    You're going back a loooong way. The E-cell "timer" was used to monitor vehicle miles. The C/E light was illuminated so the vehicle would be brought in for a checkup of the emissions system. This article shows it to be 60k miles. IIRC the scantool data stream displayed "E-Cell: Expired" after 60k.

  3. #3
    Electronic Ignition!
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    Hey thanks for that ...
    At least now I know that it is some kind of timer, I get a few more results from Google searching for "E Cell Timer"

    If I searched "E Cell Program Modifier", I just got "Do you mean Excel Programming" !

    But the schematics show only a single connection from the E-Cell to the ECM, which I assumed to be an input TO the ECM. However, if this module keeps track of miles, then I guess it must somehow receive a VSS signal FROM the ECM, right ?

    Unless it is cruder than that and just keeps track of how many hours the ignition power has been on and doesn't actually count miles at all then sends a signal TO the ECM when this timer (rather than actual mileage counter) expires ?? Just guessing, but I don't see how it can "know" that 60000 miles have been clocked up if it has no speed signal input.

    Do you know if the output is just a ground-switched discrete to the ECM (just guessing again).

    Many thanks for the response
    - Neil

  4. #4
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    Honestly, it may simply be a key on timer. I know it was to be replaced when it "expired." I do not know how the output was configured.

    I have an '82 or '83 Camaro service manual at home. I will try to remember to check for more information.

    If I searched "E Cell Program Modifier", I just got "Do you mean Excel Programming" !
    Sometimes I long for the days when a search engine displayed what you asked for rather than asking if you wanted what it displayed.

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  6. #6
    Electronic Ignition!
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    @1project2many

    Thanks - that's really helpful. My Firebird manual says the same - so it seems that the module causes the ECM to do more than just switch on the Check Engine lamp, but actually modifies its control function.
    These forum threads suggest the same:
    https://www.corvetteforum.com/forums...l-expired.html
    https://www.s10forum.com/forum/f106/...module-435250/

    I'm coming to these conclusions:
    1. It doesn't actually count miles travelled (60000), but just estimates this based on total time for which the ignition power has been on (similar to the way that printer cartidges estimate how much ink is left just by counting how long they have been powered and consequently usually report empty when they are at least half full !)

    2. The output from the module is a discrete switched input to the ECM, probably grounded before the E-Cell expires and open-circuit after it expires.

    3. This all probably indicates that the module can simply be removed on a "broken-in" engine.

    I'm in the process of building a test rig for these ECMs, so when complete, I'll check this and identify exactly what changes with this input in different states (eg injector duty cycle change when cranking).



    What I still don't understand is this:
    if the ECM switches on the Check Engine lamp when the E-Cell expires, then why isn't my Check Engine lamp on now, when I presume that the E-Cell expired about 35 years ago ?! :)

  7. #7
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    3. This all probably indicates that the module can simply be removed on a "broken-in" engine.
    Hmm. In '93, when I installed an '83 Camaro "S" intake and computer in my '57, I was working as a GM tech and had access to much training and service information. I do not remember many details of the module itself but I do remember spending much time back then learning what I could in order to effect the swap. In the end the module is not required for proper operation and was successfully omitted during my build. My truck traveled around Montana for five years then drove back to New England and ran for two on that same ecm.

    What I still don't understand is this: if the ECM switches on the Check Engine lamp when the E-Cell expires, then why isn't my Check Engine lamp on now
    I may not be correct about the light illuminating. Trying to remember these details is something like telling grandkids what sledding was like as a child. You do your best to hit all the details but once in a while, memory and facts may not exactly align. :)

    I feel like there is an old service bulletin out there that better explains the module but I was not able to find it last night. If you know anyone on a Vette forum with a database of searchable bulletins they may find it faster than I could.

  8. #8
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    Thanks again for the input. I think I have seen a few places which suggest that the module illuminates the check engine lamp.
    Will know for sure when I finish my test rig and check what the ECM does differently with this input open-circuit or grounded.
    Will post back at that time for reference.

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