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Thread: VSS killed itself?

  1. #1
    Fuel Injected! 1BadAction's Avatar
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    VSS killed itself?

    So I'm just getting this thing idling and driving down the road, made some adjustments, downloaded everything to the emulator then all of the sudden, my MPH starts reading the same as the TACH, then stops. As I go for a drive, no VSS reading in tunerpro, and no transmission shift. It's a 4L80E and a 7060 PCM. Did I just witness something in the ECM committing suicide or did the VSS itself just die? Oddly enough the electric speedo still works.
    94 Blazer, Turbo'd 350 TBI - DD
    1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
    2012 Porsche Panamera Turbo - Date night car :)
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

  2. #2
    Super Moderator Six_Shooter's Avatar
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    If you're running the speedo from the same sensor, then the sensor itself is fine. Check over connections to the ECM, if you can't find anything there, swap to another ECM.
    The man who says something is impossible, is usually interrupted by the man doing it.

  3. #3
    Fuel Injected! 1BadAction's Avatar
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    However the speedo is driven in a factory stock truck. I think the signal is split at the DRAC, one signal goes to the PCM and the other to the speedo, but I'm not sure.
    94 Blazer, Turbo'd 350 TBI - DD
    1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
    2012 Porsche Panamera Turbo - Date night car :)
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

  4. #4
    Quote Originally Posted by 1BadAction View Post
    However the speedo is driven in a factory stock truck. I think the signal is split at the DRAC, one signal goes to the PCM and the other to the speedo, but I'm not sure.
    If you're running with a DRAC (VSSB to some) and the speedometer works, the VSS should also be working. Either the DRAC output to the PCM failed or somethings up with the PCM itself. As mentioned, swapping PCM's would be a good start.
    Familiar with 1227747 and 16197427 PCMs

  5. #5
    RIP EagleMark's Avatar
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    Quote Originally Posted by 1BadAction View Post
    However the speedo is driven in a factory stock truck. I think the signal is split at the DRAC, one signal goes to the PCM and the other to the speedo, but I'm not sure.
    1991 Square body Suburban? You sure the VSS is not in speedo? Not sure with all the changes and yours is 4x4, but speedo is cable driven and VSS is in Dash.

    Could be as simple as a fuse...


    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  6. #6
    Fuel Injected! 1BadAction's Avatar
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    Mine is a 2wd, nothing electrical has been changed from stock. 91s no longer had a cable drive speedo or optical eye vss on the back of the gauge, they had the electronic VSS on the transmission.

    It very well could be a fuse, I may be getting excited about nothing.
    94 Blazer, Turbo'd 350 TBI - DD
    1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
    2012 Porsche Panamera Turbo - Date night car :)
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

  7. #7
    RIP EagleMark's Avatar
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    Ah forgot you were 4L80E... my bad...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  8. #8
    Fuel Injected! 1BadAction's Avatar
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    Well, verdict is, either it is the EEPROM or the ECM itself. I'll be ordering an ECM complete with prom this week and checking it out next weekend.

    Has anyone had trouble with reman computers? This one was already replaced once.
    94 Blazer, Turbo'd 350 TBI - DD
    1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
    2012 Porsche Panamera Turbo - Date night car :)
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

  9. #9
    RIP EagleMark's Avatar
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    Your first post said emulator, sometimes things go bad there, just takes a restart, upload verify and emulate to make it right.

    I've never had an ECM/PCM go bad and never got a bad one from JY, so I can't comment on new ones. VSS would be a more likely suspect.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  10. #10
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    if you look in my previous posts, I had the same thing happen to me a few weeks ago. 7060/80E 454. speedo still worked, trans didn't shift.
    http://www.gearhead-efi.com/Fuel-Inj...ll=1#post20340

    Durning my tuning and programming with my burn 2, I ended up somehow loosing VSS. I also had a code 51 which EagleMark had showed me (it had been there awhile). And I still have this weird datastream glitch.

    During this extremely frustrating day of tuning, I could not get the VSS signal back by programming. I thought it was just a flash error because how could it just all of a sudden loose the VSS?

    Local autozone had the computer for $99 instock. Snagged it, installed my G3 and flashed a new chip. Bingo, Everything works again.

    For some reason I still have my doubts that it was the computer for sure.....but the reman computer did fix my issue so IDK WTF.

    This is really really odd that you have the same issue as I just had with the same setup....although you're emulating.
    Last edited by chevmasta; 04-13-2013 at 05:39 PM.

  11. #11
    Fuel Injected! 1BadAction's Avatar
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    Quote Originally Posted by EagleMark View Post
    Your first post said emulator, sometimes things go bad there, just takes a restart, upload verify and emulate to make it right.

    I've never had an ECM/PCM go bad and never got a bad one from JY, so I can't comment on new ones. VSS would be a more likely suspect.
    Yes, it was during emulation... When I parked it, it was running like crap, throwing codes, not responding to anything. So last night I checked fuses, then uninstalled everything and put the computer back to stock. It wouldn't even start and run in limp home. Codes wouldn't clear, no response at all.

    Quote Originally Posted by chevmasta View Post
    if you look in my previous posts, I had the same thing happen to me a few weeks ago. 7060/80E 454. speedo still worked, trans didn't shift.
    http://www.gearhead-efi.com/Fuel-Inj...ll=1#post20340

    Durning my tuning and programming with my burn 2, I ended up somehow loosing VSS. I also had a code 51 which EagleMark had showed me (it had been there awhile). And I still have this weird datastream glitch.

    During this extremely frustrating day of tuning, I could not get the VSS signal back by programming. I thought it was just a flash error because how could it just all of a sudden loose the VSS?

    Local autozone had the computer for $99 instock. Snagged it, installed my G3 and flashed a new chip. Bingo, Everything works again.

    For some reason I still have my doubts that it was the computer for sure.....but the reman computer did fix my issue so IDK WTF.

    This is really really odd that you have the same issue as I just had with the same setup....although you're emulating.
    Very strange we've had the same problem, indeed. I wonder if it's just the old electronics? I'll see what I can find locally. I did pull the pcm so I'd have a core.

    Hopefully it's not the EEPROM
    94 Blazer, Turbo'd 350 TBI - DD
    1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
    2012 Porsche Panamera Turbo - Date night car :)
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

  12. #12
    RIP EagleMark's Avatar
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    It can't be the EEPROM during emulation and everything you said above is a sure sign something happened to emulator. SOmetimes it just happens, you need to learn the signs like above. Reload the bin to TunerPRo, Upload to emulator, Verify, Emulate, turn key on and should come on, blink and stay on till started.

    Did you set Mask ID to AA to disable checksum?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  13. #13
    Fuel Injected! 1BadAction's Avatar
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    Quote Originally Posted by EagleMark View Post
    It can't be the EEPROM during emulation and everything you said above is a sure sign something happened to emulator. SOmetimes it just happens, you need to learn the signs like above. Reload the bin to TunerPRo, Upload to emulator, Verify, Emulate, turn key on and should come on, blink and stay on till started.

    Did you set Mask ID to AA to disable checksum?
    Yes, I agree, but to diagnose it, I took out the G1, installed the stock prom, and tried it that way. Wouldn't even start. I set the PCM into limp home a couple times when emulating. I just shut everything down, waited 30 seconds, then started it back up seemed fine until right before I stopped messing with it last saturday.

    That explains why it would still run (albeit setting tons of codes) while emulating, but wouldn't run at all when I put the PCM back to stock. Sounds like it's the eeprom itself and not actually the PCM that is the problem.

    How do I set the mask ID? That should fix the issue with emulating. I think the killed PCM was my own ham-fisted fault...
    94 Blazer, Turbo'd 350 TBI - DD
    1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
    2012 Porsche Panamera Turbo - Date night car :)
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

  14. #14
    RIP EagleMark's Avatar
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    Open Mask ID and change from 85 to AA.

    You probably have a error 51 Prom Failed set in PCM, clear codes and try again. If 51 is set it won't run right even if you fixed the issue until codes are cleared. Emulating without AA sets error 51.

    Whenever I hook up to data first thing I check is Error codes.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  15. #15
    Fuel Injected! 1BadAction's Avatar
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    The computer holds that code even though it's physically unplugged?
    94 Blazer, Turbo'd 350 TBI - DD
    1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
    2012 Porsche Panamera Turbo - Date night car :)
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

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