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NO ALDL Data Stream

Discussion in 'The Garage' started by 1979jimmy350, Mar 18, 2006.

  1. 1979jimmy350

    1979jimmy350 1/2 ton status

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    I just did my swap to fuel injection. The engine runs, but i am not getting any ALDL info at all. I have tried the paper clip trick and i can't get Datamaster to get data at all either
     
  2. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    If you have a 1227747 then you should not need to apply any resistors or anything to get the data stream to show up. Make sure that you pinned your orange data wire into pin A8 on your ECM, and make sure that your ALDL is pinned the same as your scanner connector is.

    My 89 half ton had the same problem at first, it wound up that the orange data wire in the ALDL connector was in a different position. I moved the wire, and suddenly everything worked properly :)

    And as I mentioned, the `747 does NOT need a resistor put between the white / black diagnostics wire and ground to produce data. It won't cause the engine to run incorrectly, but it will cause the idle to default to 1000 rpm, and several other things to move to default values, which will skew the results of your scan.
     
  3. 1979jimmy350

    1979jimmy350 1/2 ton status

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    i am using the 730 ECM and i made sure that the wires were correct, if the memcal was wrong could that cause this issue?
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Ah, sorry, I assumed you were running TBI :D

    Lets see if we can't figure this out for you :)

    Like the `747 TBI ECM, the `730 TPI ECM does not require any sort of resistance to be put between pins A and B on your ALDL connector (the ground and white with black striped wires respectively)

    So, you need to again make sure that you've got the orange wire hooked up to Pin A8 (actually look, cause if you did a custom install, it'd be pretty easy to mess that wire up, as there are no wires to the left or right of it), and if you're sure that is good, you need to test the ECM.

    Here is an exerpt from www.ChevyThunder.com:

    "No ALDL data, won't flash code 12, light on steady: This is usually caused by a shorted (brn/wht) wire to ground, or a open wire in the ALDL terminal "A" to ecm pin A9, when the terminals "A" and "B" are connected for a diagnostic check. First try unplugging the A-B ecm connector, if the light goes off, then the brn/wht wire is not shorted to ground, and the wht/blk wire from the ALDL to ecm is not opened. Check all terminal connectors. If they check out, the problem is a faulty memcal, or ecm. If a code did not flash, the ecm should be replace using the original memcal. Replace the memcal only if a ecm swap did not correct the problem."

    Try and see if that helps out at all, if not post up here, and we'll check into other possiblities :) If worse comes to worse, I have a spare `730 I could ship to you to try.
     
  5. 1979jimmy350

    1979jimmy350 1/2 ton status

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    i do have the wires hooked up right, I am thinking that it might be my memcal, i have a flash chip in there programed for my engine but the memcal is not for a 5.7. Do you think that the wrong memcal could cause no data stream?
     
  6. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    nah, having a V6 memcal would cause some major timing issues though. A 5.0 memcal will run, but the EST stuff is different. How adverse the effect is, I don't know, but many guys seem to run 5.0 chips on their 5.7s.

    Regardless of what memcal is in there, it should still be producing a data stream...

    Does the ECM give you any codes? I once got an ECM that would turn the SES light on when you turned the ignition to on, and run the fuel pump for 2 seconds, but nothing beyond that. I discovered it was the ECM by putting a paper clip between the diagnostics in (E12) wire, and ground, which caused absolutely nothing to happen to the ECM. It should always flash code 12 to say everything is good to go.
     
  7. 1979jimmy350

    1979jimmy350 1/2 ton status

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    yea i also tried data master which uses a different wire than the ses light and kept getting the error that no ECM could be dectected
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    So are you not even getting a code 12 using a paperclip?
     
  9. 1979jimmy350

    1979jimmy350 1/2 ton status

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    no code 12 even with the paper clip
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Bulb test works though, right?

    (key in run, check engine on?)
     

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