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Thread: 4l80e limp mode problem

  1. #1
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    4l80e limp mode problem

    hey guys, I really need someones help with this. I am literally at a dead end with this. Just did a 454/4l80e swap to my 90 suburban and did a 7747(90 sub) to 7427(94 sub). Everything is running smooth none other then the tranny. I get code 81 (2-3 shift solenoid failure) and code 82 (1-2 shift solenoid failure). I sometimes get code 82 but i always get code 81. i look under current malfunction codes list in tunerpro and when the key is in the ignition position, both codes say OK. When i actually start and run the truck, thats when both or one code comes up and says error. I rechecked all my electrical and all is fine. When i ground out the pinouts at the ecm, I can hear the solenoids clicking. I even hooked the ignition feed(pink wire) to a relay to rule out that i wasnt getting enough volts. I ohmed out the solenoid through the pass thru connector and i get 11.5-11.3 ohms on both solenoids. Which i think is normal. This transmission was just rebuilt about 2-3k miles ago and i just put a transgo hd2 in the trans when it was out. I also replaced the internal harness and the external harness. Which i checked my connections about a gazillion times and all is fine. I even tried to go back to a $31 mask(bmhm) which was originally on the ecm(i switched to $OE). No change. Im pretty much at a dead end except changing the shift solenoids. Which I have doubts about them being bad since the transmission was just rebuilt 2k miles ago. What are the chances? And especially both going out at the same time. Does anybody else have any ideas? I mean my only option i seem to have is to change them. The trans has a deep pan and that means I have to remove the crossmemeber to get to the rear bolts most likely. im trying to avoid it. Sorry for the long novel. Thanks for your help, appreciate it.

  2. #2
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    I know how this sounds, but is it possible the wires are wrong between E8 and E9 on the pcm? Maybe the harness inside the transmission has them crossed........

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    It has been along time since I did anything inside a 4l80e but seem to remember the shift solenoids in the early ones and later (94-95) had different resistance solenoids. So the $31 and $OE might not be grounding them properly. You can manually test them by grounding. I think nothing grounded will give you second gear, 1-2 grounded will give you first, 2-3 grounded will give you third. It goes without saying but will say, don’t ground them both at the same time.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

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    Quote Originally Posted by c5wagner View Post
    I know how this sounds, but is it possible the wires are wrong between E8 and E9 on the pcm? Maybe the harness inside the transmission has them crossed........
    I rechecked my wiring and pinouts 10x's. And i just checked again just to be 100 percent sure, Yellow/black is in E8 and light green is E9. That is a good possibility that inside has the crossed. I know that its impossible to put the wrong connector on the wrong solenoid inside the tran y. Pretty sure i remember them being different shapes, so impossible to get backwards. Everywhere im reading it says that the solenoids are supposed to ohm around 17-25 ohms. Which mine are around 11.5. I feel either the internal harness is faulty or solenoids. But its a brand new internal harness and the solenoids were just replaced 2k miles ago. Its hard for me to grasp that they could both go bad that quick and at the same time.

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    Quote Originally Posted by myburb View Post
    It has been along time since I did anything inside a 4l80e but seem to remember the shift solenoids in the early ones and later (94-95) had different resistance solenoids. So the $31 and $OE might not be grounding them properly. You can manually test them by grounding. I think nothing grounded will give you second gear, 1-2 grounded will give you first, 2-3 grounded will give you third. It goes without saying but will say, donít ground them both at the same time.
    The engine and tranny came out of my 94 suburban which ran and drove fine right before i pulled them. No problems at all. Trans was rebuilt by previous owner before me( receipt confirmed). I did manually ground them snd heard clicking. 1-2 only grounded will give you first but i did that and it was still stuck in 2nd. Bith off will give you second gear. Mainly its only 2-3 solenoid. I havent got a code for 1-2 in the past 2 days. I even tried loading my original $31 BIN that i had in the 94 before i pulled it and same problem.
    Last edited by ph4ze; 1 Week Ago at 07:26 PM.

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    Quote Originally Posted by myburb View Post
    It has been along time since I did anything inside a 4l80e but seem to remember the shift solenoids in the early ones and later (94-95) had different resistance solenoids. So the $31 and $OE might not be grounding them properly.
    Only the force motor (PCS) changed from 93 to 94-up
    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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    Both shift solenoids grounded will put the transmission into 4th gear.

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    I think i may have found something that tells me something. When i measure reaistance between 1-2 solenoid and 2-3 solenoid i get a short(one lead on yellow/black wire and one lead on the light green wire). Doesnt matter if the ignition is on or off, it still comes up as a short. Can anybody confirm that these are two seperate circuits and are not connected to eachother?

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    Fuel Injected! brian617's Avatar
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    If you are measuring the resistance between yellow/blk 2-3 and lt green 1-2 at the PCM plug you will see the combined resistance of both shift solenoids as they share a common voltage source.
    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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    Quote Originally Posted by brian617 View Post
    If you are measuring the resistance between yellow/blk 2-3 and lt green 1-2 at the PCM plug you will see the combined resistance of both shift solenoids as they share a common voltage source.
    I see 0 ohms at the pcm plug. For some reason the pcm is not grounding the solenoids. Do you think it could be a faulty pcm? It looks like the pcm was already replaced with a used one by the previous owner because it has 95 hummer written on a sticker. It can i think only be one of two things and that is the solenoids themselves or the pcm at this point.

  11. #11
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    Quote Originally Posted by lionelhutz View Post
    Both shift solenoids grounded will put the transmission into 4th gear.
    Thanks for straightening that. As I typed was thinking of the old manual switching of both on for overdrive and then posted what I did. Must be age.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

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    Fuel Injected! brian617's Avatar
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    Quote Originally Posted by ph4ze View Post
    I see 0 ohms at the pcm plug.
    0 ohms on which 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.

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    Quote Originally Posted by brian617 View Post
    0 ohms on which circuit?
    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.
    Last edited by ph4ze; 1 Week Ago at 01:03 PM.

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    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"?

  15. #15
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    I attached a log file of the truck while its sitting in park. If anybody could please take a quick look at it, I would appreciate it very much.
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