1994 4L60E Issues

Discussion in 'GMC Truck Forum' started by timw128, Sep 12, 2016.

  1. timw128

    timw128 Full Member

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    Hello-
    I'm new here and have an issue with my 1994 GMC C1500 5.7 'K' 4L60E transmission.
    It has went into 'limp home' mode. It's been a very good truck with virtually no issues to this point.
    Checked the ECM for codes- got DTC 12 stating system's functioning. Also got codes 66, 67, 81, 82.
    If I clear the codes the truck will run fine for about a mile, and it goes into 'limp home' mode again.
    The DTC lamp doesn't come on at that point.
    I'm getting 12.5v at the transmission fuse-key on, and key on engine running. I haven't checked anything at the transmission connector yet. Darn catalytic converter's right there in the way. I did, however, unplug it and didn't see any dirt or Dexron seepage.
    I have read on other forums of people just throwing shift solenoids and parts at these things with no resolve. I don't want to do that. I am hoping to get some constructive direction here to resolve this issue. I want nothing to do with these unscrupulous repair facilities that are out there these days, either.
    Thanks for your time and consideration.
     
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  2. leolkfrm

    leolkfrm Full Member

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    12.5 with engine running?...would be low...is the voltage dropping below that when driving?, might alt going out
     
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  3. dirtrider73068

    dirtrider73068 Senior Moderator
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    What are the code definitions? 4l60e trannys if built right with upgrades parts are good trannys but stock they don't last long and tend to about 100k miles puke and blow up. It could be simple like a ground. The tranny also iirc reads from the tps and vss to control shifts points. Limp mode is there as a basic system to get off the road or home.

    If clearing the codes makes it work right then to fix or look at what codes are and go from there.
     
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  4. MrMarty51

    MrMarty51 Full Member

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    Looking in the book.
    All of the codes deals with an open circuit in the shift solenoids, TCC, 3-2 shift solenoid,2-3 shift solenoid and 1-2 shift solenoid.
    Check the grounds, all of them. Make sure that they are all clean and tight. Remove the trans pan and check for voltage at the solenoids too.
     
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  5. MrMarty51

    MrMarty51 Full Member

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    OH YEAH, Tim, Welcome to the forum.
     
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  6. timw128

    timw128 Full Member

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    Thanks for the replies. Battery should be replaced, alternator is relatively new- charges around 14v.
    MrMarty51, how do I locate all the ground points?... For some time my TPS has been scratchy, yet transmission has worked fine.
    I have a pig tail external connector I got at the auto salvage to diagnose internals, but haven't got to it yet. I can measure the solenoids for resistance and send power to them to see if there's an audible click. Just a lot of work laying on the ground working around the catalytic converter and all. I don't want to drop the pan unless absolutely necessary.
    I guess the ignition switches are unreliable on these vehicles, too, and someone makes a Power Relay bypass that fixes the transmission no power condition. It's not cheap, however the parts can be purchased at auto parts store for about $20.
    The weather's been terrible here and I don't have an inside place to work on vehicle.
    When this whole thing started last week it was intermittent and only set a code 81. Now it has these other codes, too. All leading to a no power situation. The chances of all the solenoids failing at once are very slim.
    I think I'll unplug the trans connector, check the 'e' pin (pink wire) on harness with key on, and engine running to see if there's 12v there.
    Mechanically, the transmission is sound. The 4l60e is a good trans for what it's intended for, and will last a long time if maintained and respected.
    Here are the codes and definitions-
    Code 66- 3/2 shift control solenoid
    Code 67- Torque converter clutch solenoid
    Code 81- 2/3 shift solenoid
    Code 82- 1/2 shift solenoid
    These codes happen when the ECM detects an open or shorted circuit.
    Bridging AB terminals at the ALDL starts with a Code 12 which indicates the system is function.
    Thanks again for all the thoughts...
    Regards-
    tim
     
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  7. gmctrucks

    gmctrucks Full Member

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    My old Trans blew up at around 120k on my 1993 truck it was doing what yours is so I changed out the four soliniods and it was fine oh the connectors that plug into the soliniods were super loose due to the age so I zip tied the connectors in real good I forgot how long it was that the Trans messed up again so I just bought one at O'Reilly's auto parts yes you read right from them the warrennty is good and I had a shop install it and even at that I was happy with the over all money I spent.
    Good luck! GMC
     
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  8. timw128

    timw128 Full Member

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    Thanks, gmctrucks... Yeah, I have 279K on this 1994. Never had a bit of issues with it. Changed filter and fluid, using the Valvoline high mileage Dexron, about 3-4 yrs. ago. There wasn't an unreasonable amount of gray stuff in the pan then. Truck has been well cared for. It is ready for a TPS, as there are some mild off idle anomalies.
    I didn't understand the last part of your comment, as quoted above- you meant the whole transmission?...
    My multi tester was messing up, so just went and bought a new Klein at HD. I'll check the power going to trans first, if none, I'll run a toggled and fused jumper from battery (+) spliced to pink wire going to pin 'e' in the harness, clear codes, and see if that works. If so, we'll fabricate a relay system to get around the ignition switch issue. Otherwise, we'll use our pig tail connector and measure resistance on solenoids (between 20-30 ohms), and energize the solenoids with the 12v jumper from above and check for audible clicking. Going to have to investigate possible grounding issues, too. I guess those 4L60E internal harnesses have been known to go bad. Also, I have not cleaned, with contact cleaner, the harness/trans plug in. Trans Shop told me that they have found that 90% of the time that's the culprit, especially with all 4 trans codes showing at once and the mileage involved.
    I just wish I was younger, had more ambition, and wasn't so busted up...:rofl:
    Thanks for your input.
    Regards-
    tim
     
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  9. gmctrucks

    gmctrucks Full Member

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    What I did is I bought a brand new used rebuilt Trans from O'Reilly's auto parts I was done in having them rebuilt at Joe blows shop again.

    Oh how I know how being so busted feels today they called me from the appraisals office for my house taxes I was protesting the value well they dropped the value 13k dollars that's going to help me out some I think more people should do that it works for me.
     
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  10. timw128

    timw128 Full Member

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    I meant being physically busted up. ;)
     
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