Ok, I started a new thread as the topic started to shift from the original thread titled “E4OD Transmission Problem!” created by “rmalottwtes30” just in case you want to search the back story for this thread.

I was searching on the forum and in that thread someone asked: “Did not see any one ask is your tach working perfectly and do you have a dim od light”

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So I brought in my problem:
8.26.2014
1989 F-350 Auto E4OD-= mileage ??? (45,000 on the clock but only 5 digits not sure if/how many times been rolled over)

Yeah so I'm having some of these problems. The tach sensor was not working well, it would work sometimes and not others, I looked at it and it was not looking too hot, wires looked worn and it looked like fluid was leaking past the wire connection. I replaced it and the tach still does not read at all. Also now, when I crank it, the OD light remains on and the truck feels like it does not want to get out of a higher gear. I can manually shift it but it just feels like it might be stuck in 2nd or 3rd when I put it in OD.

A lot to people are mentioning that their OD light is flashing.. mine just remains on from the start. Could that be something different?
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So then people posted some replies:
your trans control unit isn't getting power.you need to check the fuses and relays under the hood.
im unaware of where these are on your '89 though,but no doubt that's your issue.


And: TCM relay is on driverside fender close to the firewall.

And: If the light is on, on the OD switch than, OD is off, if it is on when you start it, there is a fault.

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On 9.3.2014 I posed:
Thanks for the help guys.... I feel a bit foolish now. So I popped open the hood and was looking at the electrical connections and then traced back to the tach sensor and I realized that when I replaced the fan clutch two weeks earlier I must have bumped the electrical connection on the tach sensor. The plastic connector clip has broken, being 25 year old plastic and therefore has a loose connection. Fixed it with a zip tie!
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But then on 9.17.2014 I replied:
Well I thought that I had fixed it, then the wife said when she was driving it she hit some pothole and the tach went out and it went into limp mode. Obviously there is a bad electrical connection somewhere... I just have to find it.

Unless anyone else has any advice?
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FORDF250HDXLT replied:
the most common short location for the tach is right at the tach sensor.look for bare/rubbing wires there to start.
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So that is where we are now.

 

when your tach stops working and you also have a dim (always on) OD light,it means the control unit (TCM/ECM/TECA) isn't getting power.while in this "dim od light state" if you will,the trans wont start off in 1st in the D position.never suspect the tach sensor as the faulty item until power is restored to the TECA.

when you conclude at the end; this is where im at at now.where is that? did you find and replace the relay for the trans and inspect the fuses under the hood? there are a couple fuses that when blown,wont pass current through the teca relay either and cause those symptoms (dead tach/no low gear take off in D/dim od light.)

it's also important to note (with at least the 92-94 idi trucks i know for sure) the fuel filter heating element wire runs off the circuit for the trans control unit (cheap ford wiring.) inspect (or eliminate this line,like i did on both my trucks) to avoid a short here causing the TECA to loose power when a fuse blows that supplies power to the TECA's power relay.

 

I have not found the correct relays yet. I have a few wires on the driver's side just beyond the firewall that go to nothing. These wires have plastic connector ends on them and those are plugged into caps so the wires just end and are not connected to anything. But they have not been connected to anything for the last few years that we have owned the truck and it has been working fine. So that's probably not the problem, just something I noticed while looking for relays.

I will start checking on the fuses tonight/tomorrow... unfortunately I have had other things on my honey-do list that have taken priority, but the truck is still pretty high on that list. Does anyone know where the trans relay is on my 89 F350?

I appreciate all of the help that I get from this forum.

 

a pic from someone with the e40d equipped 8th gen/bricknose idi truck trans relay would be great.

with the 9th gen,everything is handy in the power distribution box........not devoted e40d circuits like it should be,but they're easily found at least lol.

 

The tach sensor connection (old plastic) had vibrated loose ..... again. It is secure now (different located zip ties) and tach is reading fine. FYI

 

yeah but what about the dim od light (and no function of od cancel switch) and high gear starts in D?
did you find the relay yet? i can't imagine they hid it on ya that good? lol.

 

Thanks! I will check out the relay as well.

"yeah but what about the dim od light (and no function of od cancel switch)"
- For me it was never dim, it was just always on and the tach was dead. Once I cleaned the connection of the tach sensor plastic connector and made sure the connection was good and secure, I cranked up the truck and the tach worked fine and the OD light was off.

"and high gear starts in D?"
- Once the tech is working fine, it turns back ON the OD (OD OFF Light is OFF), and right then the truck goes through all of the gears just fine.

The wife said that after I reconnected the sensor connection (unfortunately that was also when the old plastic connector lock broke) she was driving the truck and all was good and then she hit a big bump or hole in the road and then all of the sudden the tach wasn't working again and the OD OFF light came on and it was in limp mode. Which tells me somewhere on that truck there is a bad electrical connection. I "THINK" I found it and we are back to normal operation.

"did you find the relay yet? i can't imagine they hid it on ya that good? lol."
- Once I got that connection secure I stopped looking for the relay, but I will definitely print this off and save it with the other electrical info on the truck and I will keep an eye out for it.

Thank you for all of your help!

 

so I have repaired the transmission control module so the diode that went bad I replaced with a 75 cent diode from radioshack, and my 89 f350 is back on the road

 

For the reference of any future people with the same problem, do you have a picture?

 

Wow...thanks for all the incredible information...so awesome....So my E-350 goes into limp mode like this...usually when I start it will be in limp mode...then I wait 15 seconds...sometimes more..a lot more..then the light goes off and all is good...but now if I shut down when I restart shortly afterwards It's usually always in limp...just tested the relay ports and sure enough relay coil power is at 9volts...any thought on the cause and how I might proceed...much thanks Benny

 

what if these symptoms are in a gas application? I have a 93 5.0 f150 with these EXACT symptoms. I replaced the EEC relay, the shift lever, the NSPS, and still have the issue. I also switched the EECIV for a reman Bc my fuel pump was constant. But that hasn’t fixed anything. What other steps could I take to diagnose?

 

Did you ever figure out why it was doing that? I have the same problem

 

You might want to send them a PM. they haven`t been around since 3/22


Charlie