Sorry Dave S, I thought the from the title the tranny was giving him fits, not just the tach, I just went through this with my e4od and just listed everything I had to inspect to fix it.

 

thank you all for sticking with me on this, ther are no idi's in the junkyards around me.
do any of your local yards have any? could any of you make a phone call , and see if they have a pcm& tach --i'm just looking to locate one , if you find one just post there phone# and i'll deal with it from there-i don't expect any of you to go pulling parts for me
thank you

 

Wow guys, I do not see any fuse boxes in my 1989 7.3 IDI SuperDuty engine compartment. I have a manual 5-speed, not an E4OD. The 2 trucks in my local wrecking yard in SOCalif have E4ODs and were manufactured in 12/88 and 12/89 and they both do not have fuse boxes in the engine compartment. None of my 1990 Ford manuals mention any PCM (Powertrain Control Module) or EEC (Electronic Engine Control) for the 7.3 Diesel, however they do show a chapter on the Transmission Control system with associated solid state TECA (Transmission Electronic Control Assembly) Module. This TECA Module is located at the "left-hand side safety wall, below brake fluid reservoir."

Hope this helps you.

 

steekers, that is what i need ! can you get me the tell phone # to that jyard please!!!

 

Joe,what you need is to trace your tach wires and possibly replace them before throwing another TECA Module at it.
yours is probably fine.it's doing its job.with no working tach= safe mode.TECA Module= working.primary objective= fix tach.

 

i chased the wires from the tach sensor they went into a conector behind the batt,on the passenger side, cleaned that from there they go ,one wire to a regulator , the othere to a harness, near the batts , then iguess the cab ,--does any body knoe witch wires that are inthe cab go to the tach? thank you

 

What sort of limp mode are we talking about here?

No power to the transmission results as follows:

2nd gear in "1" or "2"
4th gear in "D"
Reverse in "R"

Engagement in all situations may feel more positive than usual.

Or is it hard shifting and no TC lockup?

Usually this is a fuse or PCM relay. In rare cases the PCM can be ruined too. Only time we had some one with a dead PCM confirmed that I can remember was a leak in the cab that corroded the computer.

 

david 85; i have 2 nd,4th & r and i'm pulling out my hair. do you know what color the wires are in the cab for the tach, that come from the tach sensor, there is a connector just under the coloum. they have to go through there but witch ones?

 

Your tach isn't the problem, its only a symptom of the problem. On 87 and older trucks, the tach signal goes direct to the cluster but on later E4OD equipped trucks, it goes through the PCM first. No power to the PCM = no tach, and transmission in limp mode.

You need to locate the PCM relay and the fuse for the PCM to verify that they are working. Simply splicing power across the relay will eliminate this as a possible cause. All the power wires to the PCM that are solid red should have 12V in them. Referring to the diagram that Dave posted earlier, I think your PCM relay is the spot labeled TECA. That would be the first thing I would check after looking at the fuse.

Now another thing to look for is the electrical connector on the passenger side of the transmission. If thats undone, it will cause this type of limp mode, but I don't know 100% if it will ALSO kill the tachometer. The connector uses a strange type of locking tab that is easy to break and you must never use a screw driver to unplug it.

To unplug it, you press the locking tab in (toward the driver's side) while pulling up on the wiring harness. It *should* pop out upward. Look for any dirt, grease, water, corrosion, or broken wires. Some electrical grease in there would be a good idea even if you find nothing obviously wrong.

 

david 85, i have done, all the things you have suggested, i have changed the
1.tach sensor
2. the eec relay
3. replaced the under dash fuse
4. inspected the mod on the tranc
my question is,, what color wires in the connector under the steering coloum are for the tachometer cause if i get an other tach i can spice in and test
once again thank you

 

ah your in good hands now Joe.David85 knows these trans well.

 

I don't have access to a wiring diagram for that era of truck so I don't know the answer to your question. However, if you remove the cluster display, you will be able to trace the wires from the main connector to the tach.

Were you able to verify that power is actually getting in, and out of the relay? The PCM should have about 3 red wires going to it and all of them need 12V with the ignition on.

If you haven't already, you can also try disconnecting the PCM from the harness and inspecting that connector for any defects. Some trucks develop a leak in that area that can allow water in either through the wall on the side, or at the upper firewall seam joint.

 

thanks,dave85,--------i'm going back in!!!1

 

IT---IS---- ALIVE----!!!!!!!!!!!!
THANK YOU AGAIN EVERY ONE!!!
so this is what happened, i took the teca relay(brand new) off& shoved i piece of jummper wire to the to red wires comming into the female connector- and the tach came alive!!!! do ineed the relay???? does anybody need the relay on these ed04 tranns, i'd be willing to bet that connection has caused more guys more grief!!!!
and that is somthing i would never check, after all it's just plug &play but it don't play nice!!
thank you all
ps i hope my frustration, and this thread will help some one else.

 

Good to hear.

By any chance are there any other systems that are not working with the ignition on? Seems to me the 12V signal from the ignition switch isn't reaching the relay preventing the relay from connecting the PCM to 12V. So the relay could be fine, but there may not be power getting to the relay actuator.

That might be the next thing to try and jump power to.