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Thread: 4l80e limp mode problem

  1. #16
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    Quote Originally Posted by ph4ze View Post
    Sorry that im all over the place guys. I think im having a VSS issue. Im a little confused about it because there is so much misinformation out there about it. Now pin F12 controls the transmission logic side of the speed and F13 is for engine logic for speed. Am i correct with saying that? My DRAC in my 90 doesnt have an output for pin F12 like my 94 VSSB does. Which the F12 pin is supposed to see 40 pulses per rev instead of 2000 per rev on pin F13. I noticed my speedometer works but my MPH isnt displayed on tuner pro. This maybe my actual problem and why the ECM is not grounding the 2-3 shift solenoid. Anybody have a remedy for this? Could i hookup the trans output speed sensor and then set the flag "output speed not from drac"?
    You need to use a later VSSB that came with a 4l80e or 4l60e transmission instead of the drac you have now. I think they are in the dash on the left side of the glove box compartment when you remove the glove box, you will have a little rewiring but the VSSB can still be used for everything that your drac was used for like speedometer, abs, cruise, pcm, etc.

  2. #17
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    Quote Originally Posted by c5wagner View Post
    You need to use a later VSSB that came with a 4l80e or 4l60e transmission instead of the drac you have now. I think they are in the dash on the left side of the glove box compartment when you remove the glove box, you will have a little rewiring but the VSSB can still be used for everything that your drac was used for like speedometer, abs, cruise, pcm, etc.
    I actually forgot to take my VSSB out of my 94 suburbab before i junked it. So now im going to have to buy one. Do you know the 3 letter code or part number for the correct VSSB that i need? But couldnt i just wire the output speed sensor on the actual tranny to pin F12? Instead of having to do a bunch of rewiring. Also i dont think the output speed missing would put the transmission in limp mode

  3. #18
    Fuel Injected! brian617's Avatar
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    Quote Originally Posted by ph4ze View Post
    0 ohms when i put the probes between pin e8 and e9, the ecm to shift solenoid wires. Is that normal. I would think they would only be on the same circuit when the are grounded and on. I am replaci g the 2-3 solenoid to see what happens. If that fails i guess my only other option is to replace the ecm. All my wiring checks out. No shorts in the wire.
    If you have zero resistance when probing e8 and e9 at the PCM connector unplugged and the transmission harness connected you have an open circuit.
    89 K1500 Scottsdale 5.7L 5spd 3:42

    Build specs: 97 4 bolt main block 350ci, Eagle rotating assembly with flat tops and 4 valve reliefs, Dart 165cc/67cc Iron Eagle heads, Manely SS valves and springs 110lbs seat @1.7, GM Ram Jet cam 196/206 @.50 .431/.451, stock intake and throttle body, heads and intake gasket matched, Delco EP377 fuel pump @ 22 psi, 427 PCM.

  4. #19
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    Quote Originally Posted by ph4ze View Post
    Also i dont think the output speed missing would put the transmission in limp mode
    The PCM can't properly perform speed based shifting calculations when it doesn't have a speed signal.

  5. #20
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    Found what my problem was and it was literally a 30 second fix. Instead of putting the tranny power feed on a hot all the time, i feed it with an ignition wire. That was what was tripping the code 81 and 82. Been chasing this for a week now and it was something so simple. I want to slam my head against a wall.

  6. #21
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    Quote Originally Posted by ph4ze View Post
    Found what my problem was and it was literally a 30 second fix. Instead of putting the tranny power feed on a hot all the time, i feed it with an ignition wire. That was what was tripping the code 81 and 82. Been chasing this for a week now and it was something so simple. I want to slam my head against a wall.
    Haha, I did the same thing when I did the 350 TBI swap in my jeep. I used an accessory key on wire that didn't have power during cranking.... Could not figure out why it wouldn't run for about a week either......

  7. #22
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    Quote Originally Posted by ph4ze View Post
    Found what my problem was and it was literally a 30 second fix. Instead of putting the tranny power feed on a hot all the time, i feed it with an ignition wire. That was what was tripping the code 81 and 82. Been chasing this for a week now and it was something so simple. I want to slam my head against a wall.
    Try this

    LOL

  8. #23
    Fuel Injected! brian617's Avatar
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    The 12v supply should only be hot in start and run only, not +B voltage.
    89 K1500 Scottsdale 5.7L 5spd 3:42

    Build specs: 97 4 bolt main block 350ci, Eagle rotating assembly with flat tops and 4 valve reliefs, Dart 165cc/67cc Iron Eagle heads, Manely SS valves and springs 110lbs seat @1.7, GM Ram Jet cam 196/206 @.50 .431/.451, stock intake and throttle body, heads and intake gasket matched, Delco EP377 fuel pump @ 22 psi, 427 PCM.

  9. #24
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    Quote Originally Posted by brian617 View Post
    The 12v supply should only be hot in start and run only, not +B voltage.
    Where can i find this? In the ingition harness?

  10. #25
    Fuel Injected! brian617's Avatar
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    What year, make, model harness are you using?
    89 K1500 Scottsdale 5.7L 5spd 3:42

    Build specs: 97 4 bolt main block 350ci, Eagle rotating assembly with flat tops and 4 valve reliefs, Dart 165cc/67cc Iron Eagle heads, Manely SS valves and springs 110lbs seat @1.7, GM Ram Jet cam 196/206 @.50 .431/.451, stock intake and throttle body, heads and intake gasket matched, Delco EP377 fuel pump @ 22 psi, 427 PCM.

  11. #26
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    Quote Originally Posted by brian617 View Post
    What year, make, model harness are you using?
    Im using the original 90 suburban harness that was in the truck. I seen tge 1619427 pcm has a ignition output on it. Thats what my electrical diagnosis book says. Could i use that?

    Also so my threads where my gear linkage bolts onto broke off. So i bought a new shift shaft. Open the trans and goto remove the shift shaft retaining pin. Thing breaks clean off flush. Ending up having to drill holes around it to grab it. This tranny does everything to try to screw me LOL

  12. #27
    Fuel Injected! brian617's Avatar
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    What original engine/transmission for the original harness youre using?
    89 K1500 Scottsdale 5.7L 5spd 3:42

    Build specs: 97 4 bolt main block 350ci, Eagle rotating assembly with flat tops and 4 valve reliefs, Dart 165cc/67cc Iron Eagle heads, Manely SS valves and springs 110lbs seat @1.7, GM Ram Jet cam 196/206 @.50 .431/.451, stock intake and throttle body, heads and intake gasket matched, Delco EP377 fuel pump @ 22 psi, 427 PCM.

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