E4OD Light on, stuck in 4th gear

Discussion in '6.9L IH & 7.3L IDI Diesels' started by ISPKI, Jan 8, 2017.

  1. ISPKI

    ISPKI Full Access Member

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    Hey Folks. I have a 1994 F250 7.3idi n/a with the e4od and this damn transmission has been causing me all kinds of trouble.

    A few weeks ago, while driving to work, the "OD OFF" light came on and wont turn off, it feels like its stuck in 4th gear and wont shift out of it. I can shift it into 1st, 2nd etc with the shifter just fine which is how I got it home. The tachometer stopped working as well.

    I read that this is most commonly caused by the engine speed sensor, so, I got in touch with a local idi owner (has a 93 f350) who let me come by and swap that sensor to see if it was causing the issue. I swapped it out but no change, still cant shift when in drive.

    Is there anything else that could be causing this? Anyway I can test to see if maybe a wire in the harness is broken, or something at the tachometer is broken? I plugged my obd1 scanner into it but it didnt read any codes.

    I am waiting on an LUK clutch, flywheel, and hydraulics for my ZF5 swap which I was not looking to do for a few more months, but it doesnt look like I have much of a choice.
     
  2. cpdenton

    cpdenton Truck needs paint. Supporting Member

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    IMG_0271.JPG You have Lost power to the Transmission control unit most likely.

    Check fuse U and the TECA relay.
     
  3. gandalf

    gandalf Senior Member

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    Okay, you tried the tach sensor on the IP gear housing? You actually switched it out with one from another truck, and there was no difference? That was the first and most obvious cause.

    Next, how does the speedometer work? The sensor for the speedo is on the differential, high on the frontside, and will cause E4OD problems. If the speedometer is working well, don't mess with that sensor.

    It seems to me there is another possibility. Strange as it may seem, I'm pretty sure the tail light will/can be problematic for the E4OD. So, check the tail lights, the brake lights, the turn signals, the 4 way flashers. You might need another person for this, sitting in the truck.

    That's a definite maybe. But it's an easy fix if it is causing the problem.
     
  4. icanfixall

    icanfixall Official GMM hand model

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    Is your tach working correctly??
     
  5. ISPKI

    ISPKI Full Access Member

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    Gandalf, yes, I swapped the engine rpm sensor on the IP gear housing with one from another truck and it did not fix my problem. Speedo works fine, all tail lights work fine.

    Icanfixall, tach does not work at all, sits at 0, hence why I thought that sensor blew.
     
  6. cpdenton

    cpdenton Truck needs paint. Supporting Member

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    Your tach signal goes through the TECA before it gets to the gauge. If the TECA has no power, your tach goes dead.
     
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  7. gandalf

    gandalf Senior Member

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    The tach must work properly in order for the E4OD to work properly. If the tach is not working then there is no RPM signal going to the transmission computer. Without that signal the E4OD computer cannot perform it's function, and puts the transmission into limp mode. Unfortunately I think you'll probably get into the more technical aspects now, where fewer of us will be able to advise you.

    My only suggestion at this point would be to check the cabling connections to the transmission, where the cable attach to the transmission. You'll be looking for that connection on the passenger side, behind a shield.
     
  8. ISPKI

    ISPKI Full Access Member

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    Great, I will look into everything you guys have mentioned starting with the fuse and relay for the TECA. Are the relay terminals clearly marked so I can test the functionality of the relay?
     
  9. ISPKI

    ISPKI Full Access Member

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    So the fuse is not blown, although it is also the incorrect size according to the schematic that CPDenton posted. I have not had time to check the relay, too much work and 3 degree weather today. Pleasantly surprised that the truck actually fires up in near 0 degree weather.
     
  10. cpdenton

    cpdenton Truck needs paint. Supporting Member

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    Stole this from another thread. GREAT info here.


    Post #7 on this thread.
    http://www.oilburners.net/threads/tach.79067/


     
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  11. trackspeeder

    trackspeeder Stone crusher.

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    If the OD OFF light is dimly lit there is no power to the TCM. Check the relay.
     
  12. NOAH MATTEOLI

    NOAH MATTEOLI Registered User

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  13. ISPKI

    ISPKI Full Access Member

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    It is very dim, difficult to read without cupping my hands over it. I will swap the relay out today after work. I believe I have some spare relays in the glove box, not sure if any of them work but I will take the suggestions posted earlier and test them with the horn relay position.
     
  14. ISPKI

    ISPKI Full Access Member

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    Solved! TCM Relay was bad. Swapped in a spare and the OD light is off. Shes warming up now, going to go for a spin in a few to make sure.
     
  15. icanfixall

    icanfixall Official GMM hand model

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    Well that's great news. Now for some info on that relay... It receives power from the passenger side fender mounted solenoid. It then has a fusible link found behind the battery on that side. I too had issues like yours last year. I replaced everything including the tach. It worked till I really needed my truck. then it crapped out on me but drove it anyway. Did plenty of teca relay search and found it needed power.turns out it has several circuits. One is power on all the time. another is power on with key on. So I used my multi meter and found no power to the key on circiut.So made a jumper from the drivers side battery and had a tach signal finally. Drove fine. So started tracing the wires from the relay back to the solenoid. That is how I found where the wires got power. Someone long before me made 3 wire splice repairs behind the battery in about a 3 inch mess on the same fusible link. So went to a wrecking yard and cut out the fusible links and spliced them into my harness. Shrink tubing and RTV and electrical tape fixed that mess. Now I have several fuseable links waiting for a need. I had plenty of help here and from Utube. Electrical shorts are not my field of knowledge...
     

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