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Trying to work out the trouble code issue w/my TBI swap...HELP!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlueOx, Dec 26, 2002.

  1. BlueOx

    BlueOx 1/2 ton status

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    Now that I have some time on my hands I need to work all the bugs out of my TBI swap. Here are a few things that I need to fix. When I first finished the swap the SES light would come on when I was driving so I pulled the codes and got a few but never wrote them down. One day the light stopped coming on. I didn’t fix any of the problems nor is the light bad. When I pull the codes now all I get is code 12. I was thinking that a power wire to the computer was connected wrong, thus resetting the computer when I turn it off. I have the main power wire set as always HOT. I want to get the WINADAL program to use but if it shows no codes will it work?

    I have disconnected the battery cables to try and reset the computer but it did no good. Can the computers “Learn” and adapt if so is there anyway to reflash it? Any help on this matter would be greatly appreciated.

    Thanks,
    Charles
     
  2. jmd

    jmd Registered Member

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    At this point, the code has been lost for certain because of disconnected power to the ECM. The ECM does have some adaptability & memory, but if it's not giving a code any longer, and you don't know what the code was, there's way too much that it could be to go try & troubleshoot now. Get a scanner to monitor the sensors, or forget about it until the code comes up again

    -Matthew
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    WinALDL will work, as it shows you whats going on with the system "live". It's not like it only shows you codes.

    As I understand it, the ECM does "learn" up to a certain point, and I'm sure its not a one way street. If this makes any sense, if it is getting wrong data for awhile, (bad O2 sensor for instance) it won't keep operating on the old data when you put in the new sensor, it will adjust for the change. Kind of a bad example, but I think you see what I'm saying. Basically, it always tries to run how it was programmed, if its important enough, or occurs long enough, a code will be set if its outside of the "optimal" parameters.

    As I recall you have the service/electrical manual for the donor, it should tell you which wire is hooked to what. You may need to follow the power wires from the ECM to the fuse panel, get the fuse panel circuit # from that diagram, then examine the fuse panel diagram itself to understand which circuits you are dealing with are supposed to get power, and when, and where they should be connected on the fuse panel.
     
  4. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Code 12 is a diagnostic check, everything should be good.
     
  5. BlueOx

    BlueOx 1/2 ton status

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    I checked all the wires and they were in the same place as they were when I finished it the first time. The thing is everything was working fine then the codes just went away. Is there away to reflash the ECM or should I just look for a new one. I would really love to figure this out. I dont have a sevice manual but are there any books that explain what all the values are in the WINALDL program.

    Thanks,
    Charles /forums/images/graemlins/laugh.gif
     
  6. HarryH3

    HarryH3 1 ton status Author

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    To reset the ECM you just have to disconnect the power for a few seconds. It will then revert to the factory programming. If it isn't showing any codes, then whatever the problem was, it doesn't exist right now. /forums/images/graemlins/cool.gif
     
  7. BlueOx

    BlueOx 1/2 ton status

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    HarryH3, I tried to te disconnect thing but no dice, I would love to thing the problem is solved now that it shows no codes but I never hooked up a VSS, 02 sen, knock sen,nor is the timing correct.

    Charles
     
  8. HarryH3

    HarryH3 1 ton status Author

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    If you left all of that stuff disconnected, but still don't get an error codes or a check engine light, then the ECM is toast. Does the check engine light come on for a few seconds when you first start the engine? Times like this are when a good scanner is really handy to have. It will tell you a LOT more than that silly flashing light. /forums/images/graemlins/shocked.gif WinALDL will probably help you diagnose it as well. I haven't played with it yet, but from what I've read it's a pretty useful tool! /forums/images/graemlins/thumb.gif

    Make sure that the check engine bulb isn't just burned out. /forums/images/graemlins/wink.gif
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Think you'll have to just get winaldl and play with it/check places like www.thirdgen.org to see what everything means.

    You said that the bulb is good, make sure that however those things are run is ok too. IIRC, the check engine/code lamp is grounded by the ECM. ECM grounds are all good?
     
  10. BlueOx

    BlueOx 1/2 ton status

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    I checked the one ground wire that I have on the frame and I drove it work today. I got about half way there and the SES light came on. Man, I was happy. I took all my stuff out of the Blazer to put in my car and got back in and the light was off. Man, I was mad. I parked the truck and pulled the codes and got a 24 {VSS}. I drove the truck home and messed w/the wires some more and found all the grounds were good. I know you are going to say get a scanner but I want the light to work too. Imight just swap out the ECM and see if I get a light.

    Other than a bad off idle the stumble, the truck runs real good.

    Charles
     
  11. HarryH3

    HarryH3 1 ton status Author

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    WIth all of the sensor inputs that you don't have, the ECM is always going to run in "limp home" mode. /forums/images/graemlins/frown.gif It won't be able to fine tune itself, so it will just run with the basic fuel and timing curves that are hard coded in the PROM. That mode is just intended to make the engine run well enough that you can get somewhere to have it fixed. I doubt that you'll ever be happy with the way it runs until you have all the sensors connected properly.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Only problem I have with him running in limp mode (which he is obviously) is that his SES light should be on, and he should have more codes than he can count. Even if the SES driver was intermittent, when it spits codes, it should spit all of them. /forums/images/graemlins/confused.gif
     
  13. HarryH3

    HarryH3 1 ton status Author

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    Yeah it should be choking on error codes. I don't know if there's an internal limit to how many it can store or not. I'm sure the GM engineers never imagined everything failing at one time. /forums/images/graemlins/wink.gif No telling how the computer will react with than many inputs missing. /forums/images/graemlins/frown.gif
     
  14. Thunder

    Thunder 3/4 ton status

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    Yeah you will never get it to run rite without the sensors. Espiclly the O2. it is vital to proper operation of the FI system. Without it you might as well go back to a carb.
    To get it running rite get the sensors hoked up.
    you can probabally get by without the VSS but you need all the rest of them.

    When the computer goes into Bypass mode (limp Home). it totally ignores all input from the sensors. It wont even show some of them on a scanner. The only values that show up are the pre set ones. And after a certain ammount of times( 25?) the ignition switch is turned on and off the Check engine light wont come on any more either. I also think it will dump the trouble codes too.
     

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