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Thread: Corvette CCM Reverse Engineering Anyone?

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  1. #1
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by -=Jeff=- View Post
    Not sure Lingenfelter bought them all. Jerry's Gaskets has tons of parts. Only had to find parts, CCM, ECM and Ignition Module, but the IM is pretty stout..
    I was referring to the hard parts like blocks, heads, intakes, cams and crankshafts. You know, the other type of "magic smoke" where the fire is ignited by metal-on-metal type catastrophic friction.

    Quote Originally Posted by -=Jeff=- View Post
    I am debating on buying a 1994 CCM for testing purposes, but have 4 others so not quite sure I need it. I need to finish my test bench which will add functions to the ECM Simulator for some of the cluster displays..
    AngryCorvair's donor is out of a 94. I'd loan it to you if it would contribute to your quest.

    Thanks for sharing what you have. Once we have this nut fully cracked we can move on to the C5 and OBD-II / J1850 VPW based stuff. Who's with me!?! [crickets]

  2. #2
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    Quote Originally Posted by spfautsch View Post
    Once we have this nut fully cracked we can move on to the C5 and OBD-II / J1850 VPW based stuff. Who's with me!?! [crickets]
    I would be down, if only because the fact that Rob Dahm has stuffed a stock PCM and entire throttle body into the fender of his rotary-swapped C5 drives me absolutely freaking bonkers. There is no reason to do that when all he actually wants to do is make the dash happy.

    Just...yanno...need to actually get my hands on a C5 first.

    As for the flag in 92-93 for LT1 vs LT5, technically the CCM does have the code for that error message. However, figuring out what those error codes are actually querying is the territory of the real nerds here. Someone like kur4o would need to take a crack at disassembling the CCM code and looking for the routine that the CCM runs to trip the error flag for DTC 81.
    1990 Corvette (Manual)
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  3. #3
    Fuel Injected! -=Jeff=-'s Avatar
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    Actually the error I would see for the 90-91 want C41. So it could be either, C81 was not on the 1990-91

    Here is my better version of my bench. The green PCB is an old ECM setup made on Thirdgen or anothe site years ago, it has some POTs. I want to test my message reader that will be based on Nomake's code

    The screen is a 4.3 version of the 5" version in my car. It replaced the basic DIC. I am working on adding the data from the ECM to CCM. This is an older screen and I want to see if I can make a second page that is touch accessible
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    1990 Corvette ZR-1
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  4. #4
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    Oh, you're right, 81 wasn't in the 90 definition. But I was more talking about the 92-93 CCM anyway. Interesting that in the older CCM, getting the 'wrong' bit on the reply would just make the CCM pretend like the ECM wasn't even there. Silly GM.
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  5. #5
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by NomakeWan View Post
    Oh, you're right, 81 wasn't in the 90 definition. But I was more talking about the 92-93 CCM anyway. Interesting that in the older CCM, getting the 'wrong' bit on the reply would just make the CCM pretend like the ECM wasn't even there. Silly GM.
    Haven't been getting email notifications again - and I'm completely lost here is C41 / C81 a dtc or ???

    Anyway, I finally had some time to work on modding my logger so it will write all ALDL data to the sd card. That's now working so I should be able to capture the initial interaction between the PCM / CCM very easily with VATS enabled / disabled in the CCM, and with / without the correct PASSKey resistor. But now I'm remembering how rough my code example was where I left it. There's a lot of cleaning up, general stupidity mitigation, and function modularizing needing done. Ugh.

  6. #6
    Fuel Injected! -=Jeff=-'s Avatar
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    Quote Originally Posted by spfautsch View Post
    Haven't been getting email notifications again - and I'm completely lost here is C41 / C81 a dtc or ???

    Anyway, I finally had some time to work on modding my logger so it will write all ALDL data to the sd card. That's now working so I should be able to capture the initial interaction between the PCM / CCM very easily with VATS enabled / disabled in the CCM, and with / without the correct PASSKey resistor. But now I'm remembering how rough my code example was where I left it. There's a lot of cleaning up, general stupidity mitigation, and function modularizing needing done. Ugh.
    yeah the C81 and C41 are CCM DTCs when the ECM/PCM is not present or not recognized.

    As fit the code stuff. Yeah that always happens
    -=Jeff=-
    1990 Corvette ZR-1
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  7. #7
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    DTC 81 is “Engine Configuration Mismatch,” and must have been added in 1994 when the diagnostic message protocol changed.

    DTC 41 is “ECM Serial Data Loss” and indicates a lack of response to the $40 poll.
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  8. #8
    Fuel Injected! -=Jeff=-'s Avatar
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    Quote Originally Posted by spfautsch View Post
    Haven't been getting email notifications again - and I'm completely lost here is C41 / C81 a dtc or ???

    Anyway, I finally had some time to work on modding my logger so it will write all ALDL data to the sd card. That's now working so I should be able to capture the initial interaction between the PCM / CCM very easily with VATS enabled / disabled in the CCM, and with / without the correct PASSKey resistor. But now I'm remembering how rough my code example was where I left it. There's a lot of cleaning up, general stupidity mitigation, and function modularizing needing done. Ugh.
    Would be more than willing to try out this when you get it further along. I am running out of driving time, weather getting crappy. I am also working on my Display and going to try an read messages off the bus (first going to start with the Simulator on my test bench. I just need to get a level shifter for the DUE..
    -=Jeff=-
    1990 Corvette ZR-1
    Black/Red Interior

  9. #9
    LT1 specialist steveo's Avatar
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    don't really have time to get the ccm test bench set up again - but let me know if i can build any more crap into flashhack to help, it's a good platform to add crap to, to test whatever on an aldl bus

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