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Thread: wont rev past 4000 RPM?

  1. #1

    wont rev past 4000 RPM?

    Im trying to swap an 07 6.2L with VVT using an e38 into a Camaro with a t56. I have it running fine and no codes but I cannot seem to get the PCM to read VSS signal and when i drive it it will not rev higher than 4000 RPM before it cuts off. Ive tried messing with the fuel cut offs and no luck. I have the VSS wired into pins 71 and 72

    Anyone have any idea?
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  2. #2
    Tuner jon6.0's Avatar
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    Some Corvettes have a launch control that will hold the RPM at 4000 with the pedal floored just prior to launching. I wonder if that's somehow involved?
    2014 ZL1. Manual trans.

    2011 Silverado 2500HD 6.0 gasser, 6 speed auto

  3. #3
    I know of this my brother in laws 10 Grand Sport has it but I dont think thats the case here at all. Its either something with a cut off or torque management that I cannot easily find or it could be a wiring issue. I heard on another board that it could be pin 9 the brk sw sig as I do not have it hooked up and mayeb the ECM thinks Im still in park? Im going to wire it up to something when I get back in the shop.

    Unless someone sees something in that tune thats screwed?

  4. #4
    Tuner in Training
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    Try making your Cold Engine cut off all high too. I notice when its really cold it's set to 4k. If your computer isn't reading the ECT right, it'll register at -40

  5. #5
    Good tip it cant hurt to try

  6. #6
    HP Tuners Owner Chris@HPTuners's Avatar
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    use the scanner to log:
    - ETC Source
    - Fuel Cut Type
    - ETC TqMgt Type
    - Spark TqMgt Type
    - Fuel Cut TqMgt Type
    I count sheep in hex...

  7. #7
    Try making your Cold Engine cut off all high too. I notice when its really cold it's set to 4k. If your computer isn't reading the ECT right, it'll register at -40
    Just tried that with no luck

    use the scanner to log:
    - ETC Source
    - Fuel Cut Type
    - ETC TqMgt Type
    - Spark TqMgt Type
    - Fuel Cut TqMgt Type
    Setting up to do this right now

  8. #8
    Heres the log. Still no VSS im at a loss
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  9. #9
    HP Tuners Owner Chris@HPTuners's Avatar
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    ok the problem here is that your ECM is from an auto trans vehicle and it is hitting a default torque limit because the TCM communications are down. This is also the reason your VSS signal is zero becuase the ECM expects to receive the VSS signal from the TCM (where it is wired to) via the comms bus.

    Chris...
    I count sheep in hex...

  10. #10
    Yes I agree its definitely not liking the VSS straight from the t56 but there are quite a few other swappers on LS1tech etc that have done this same swap with success so we must be missing something.

    Whats the difference in terms of signal feed between the TCM and straight from the VSS aside from pulse? I noticed I can change the pulse in the VCM editor which I tried messing with but no luck.


    I really hope your not telling me Im up the creek without a paddle are you?

  11. #11
    Im wondering if it thinks Im still in park? I didnt hook up pin 1 ( as none of the diagrams I viewed on swaps such as this havent either ) but maybe in my case it requires a signal? Im grasping here...

    Anyone know if its suposed to ground or 12v+ or what? I dont have any diagrams for where it goes unfortunately.

    I think half my problem is Ive done a bunch of LS1 harnesses with ease and never had a blip of a problem but this gen IV stuff is a lot trickier to trick so to speak.

  12. #12
    Senior Tuner edcmat-l1's Avatar
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    Just do a write entire with a manual OS.

    EFI specialist
    Advanced diagnostics, tuning, emissions
    Tuning all GMs, Ford, Mopar, Nissan GT-Rs, Evos, WRXs, Euros
    email=edcmat-l1@msn.com

  13. #13
    Quote Originally Posted by edcmat-l1 View Post
    Just do a write entire with a manual OS.
    Cant do. Im running a custom grind VVT cam and theres no OS with manual trans and VVT that I know of. What I am thinking of doing though is doing a complete re-write with an 08+ Escalade OS. Either that or simply buy a new ECM from an 08+ and try it. Ive searched everywhere for answers o this and I have found a few very similar problems with other swappers and the only common thing is we are ALL on 07 engine/ecm's. I have found plenty of guys who swapped in 08 and newer L92's running t56's and even a boat builder with no VSS and they dont have this same problem of mystery 4000 RPM fuel cut.

    I know these e38's are sensitive to custom OS flashes though. Does anyone think this is wise to completely re-write my ECM with an 08 file? Am I asking for trouble or not?

  14. #14
    HP Tuners Owner Chris@HPTuners's Avatar
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    email your file to support and i will add the default torque table and also change the trans type to manual, you should be able to get the VSS working by changing the source to repTOS or something.

    It may get things working, but there might be another couple of mods i need to make to the file.

    As suggested by others, most people use a manual OS but i guess you are stuck due to the engine type.

    Chris...
    I count sheep in hex...

  15. #15
    Quote Originally Posted by Chris@HPTuners View Post
    email your file to support and i will add the default torque table and also change the trans type to manual, you should be able to get the VSS working by changing the source to repTOS or something.

    It may get things working, but there might be another couple of mods i need to make to the file.

    As suggested by others, most people use a manual OS but i guess you are stuck due to the engine type.

    Chris...
    Mint thanks!!

    I think I'll just email my factory file and start again as Ive butchered through a lot of things trying to sort this out. Sending now

  16. #16
    Any luck with this? It would be mint to get this wrapped up before the snow flies up here so I can road test it. Its only been a freakin year and a half long build lol I just need to go fast

  17. #17
    Chris.... You da man

  18. #18
    Advanced Tuner
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    fixed?

  19. #19
    Yep works mint too the thing flies but its in need of timing and a/f and all that so im not beating on it much right now but a few hot passes to scare the neighbors is enough for tonight

  20. #20
    Advanced Tuner
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    Quote Originally Posted by cam View Post
    Yep works mint too the thing flies but its in need of timing and a/f and all that so im not beating on it much right now but a few hot passes to scare the neighbors is enough for tonight
    That's awesome!

    Quote Originally Posted by Chris@HPTuners View Post
    email your file to support and i will add the default torque table and also change the trans type to manual, you should be able to get the VSS working by changing the source to repTOS or something.

    It may get things working, but there might be another couple of mods i need to make to the file.

    As suggested by others, most people use a manual OS but i guess you are stuck due to the engine type.

    Chris...
    Any chance in making this available in a beta for us? I don't think you can get a manual trans anymore, making this type of fix more and more common.