Just fired up our 94 cat/allison Breakaway to find engine starts and runs fine but key pad shift selector is completely blank. All was working fine 24 hours earlier. We are fortunately stuck in our yard and not on the road. I'm looking for some troubleshooting hints from anyone that may have had a similiar problem as I don't want to tow to a service facility just yet as am a hands on owner for repairs thanks, bob

1) Transmission ECM fuse inside of the battery box! Corroded fuse holder! Replace the fuse even if it doesn't look or test out bad. Check these first.

2) The ECM on most Allison Transmissions are always fed power. The problem with this is that the power wire could be corroded internally or at a butt connector. The dampness in the wire could have corroded it away. (Sound familiar?) If you don't find anything by looking and testing then feel the power feed wire, it could be pregnant(have a lump in it) and not allowing the power to get to the ECM.

3) Unlikley but check the ground at the battery.

4) Start over again - you might have missed something - Don't mess with the Control Panel!

I slept on it a little more last night and woke up with another thought. The Allison Automatic may not always get it's power from "the battery" but it should be on it's own full time power supply. They do this because they want the maximum amount of power to it without the OEM wiring giving it a voltage (eratic symptoms) drop. They still have a key on feed wire. It just excites the ECM's internal relay.

---Anyway, I have seen the "main" power wire in three additional places on "Rv's/Coaches and Busses".---

The battery cuttoff switch

The starter battery post at the isolator

Positive post at the starter.
I still believe it to be a main power supply problem.

I'm sure you checked all of the fuses in your dash. Did you loose anything else, like heater control? The newer Allisons won't let you start up unless the ECM has enough voltage, but back in 94 I think you could.

had ecm replaced at allison repair shop less than a year ago and at that time was told low supply voltage was reason for failure. They hard wired new ecm direct to chassis batteries. Up till now we have been trouble free. bob

How many people have paid "experts" to do something only to have it fail?

Hum, I see that everyone here has raised there hands.

Here's the scoop - Not all experts do, do diligence! I would still check the items mentioned. It does not take very long for a "Power Feed" wire to "rot away" I have seen failure in as little as 2 days on ECM wiring during the winter months. Yes, 2 days!

I get paid to chase trucks along the highway every day of the week.

The "expert" could have put in a butt connector and not sealed it, the zip ties that he used might have been pulled so tight that it cut into the ECM feed wire, the fuse holder could have a defect in it allowing moisture in, you could have had a rock nick the wire in the summer time and once the moisture hit it might have rotted it away.

Who knows, and unless you check you won't either.

Lets say you pay to have it towed. The garage could tell you anything. If you find it for yourself you'll get the satisfaction of learning something and save a lot of money. Win, win.

Do you live in a moisture laden climate? Have you driven on slushy roads recently? It could be the most common problem I see... rotted away wiring. This is the time of the year that it happens the most. Do yourself a favor and check it out. I would hate to see you with a tow bill and mechanical repairs for nothing more then a fuse or corroded wire.

And if it's not that then, I don't know what else to tell you. At that point roadservice or tow it.

If you had power to the control panel I would teach you how to draw out trouble codes and reset things. Heck, I could teach you how to check the fluid level on most allisons (not all) without ever removing the stick! Without ECM power you have to start at square one.

The only reason I spent time writing that piece on corroded wiring was the "insane volume" of calls that I have been doing for that alone. ECM wiring, Kwikee steps, tap in wiring to the battery, you name it and it's failing.

Good luck and keep us informed. I hope you don't need a tow.

quote:

Originally posted by Bill N.Y.:
I have seen failure in as little as 2 days on ECM wiring during the winter months. Yes, 2 days!

How wiring fails in as little as two days.

.

beeoh, it's been 8 days since your first post on this problem. I was wondering, what happened?

Did you tow it? Did you get a new ECM? What was the failure? How were you treated by whoever worked on you? Did you get to go on your vacation?

BTW, Auto Zone now has the sealing connectors with the heat-shrink sleeve.

quote:

Originally posted by Bill N.Y.:
beeoh, it's been 8 days since your first post on this problem. I was wondering, what happened?

Did you tow it? Did you get a new ECM? What was the failure? How were you treated by whoever worked on you? Did you get to go on your vacation?

Just got back from our trip to Arizona..blank display problem was solved in my driveway by replacement of a relay in OEM VIM module supplying power to allison shift selector..had no problems in 3000 mile trip...thanks for all the helpful troubleshooting posts...bob

Glad you had no problems!

BTW, if anyone contemplates installing crimp connectors, do yourself a favor and get real crimp pliers - they're around $20-30, and well worth the price.

Hello,
I've a 2004 GMC C7500 with Allison 2000 series. I also don't have shift selector display on dash and no power on forward gears. Reverse goes fine. I don't have any trans service light. Truck was sitting for about 10 months and was fine before that.

Changed: Checked all fuses ; changed Neutral switch; changed ignition switch and now TCM.

Any suggestions on what the issue can be?

Thank you

Gus

I put a 2000 in our Barth. It uses a cable shifter for gears 1 thru 4. If the TCM errs out or fails for any reason the transmission defaults to 3rd gear in converter mode when shifted into any forward gear, making a dynaflow out of it.

Now go underneath snd have someone run thru the gears with the engine off. On the left side of the engine you should see see the lever move. If not it means you have an electric shifter installed such as Stone Bennent. You may have now found your problem.