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Old 05-28-2016, 10:43 PM   #1
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Coach won't start--keypad blank

Tried to do my "homework" by researching past posts but didn't find an exact match for my situation. After several starts and stops today, returned to storage but Allison MH3000 wouldn't shift out of "Drive". Shut off engine but then wouldn't re-start, no display on keypad except for red light in "econ mode" indicator. Was able re-start engine using solenoid by-pass but warning light on dash indicates "Do not shift"--still no display on keypad. Have checked all known fuses consistent with earlier posts on this forum--all circuits seem ok.

Questions:
1- TCM/ECM is under front dash, have cleaned all three module connections. Also checked keypad connection and multi-plug on tranny itself--no issues found. Is there another Allison control module somewhere that I need to check????

2- If I remove the ECM from under the dash, can it be bench-tested somewhere--like at a Steward-Stevenson shop or sent to an Allison facility for testing?


3-If it is the ECM--can you buy a rebuild or must you buy new?
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Old 05-29-2016, 09:31 AM   #2
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My coach had a similar problem which turned out to be a broken wire in the harness between the Allison computer (TCM) and the shift pad. Here's a link to a troubleshooting process that may help you isolate the problem.

Troubleshooting Allison Electronics

I did some of the things in the process and determined that my shift pad had no power at all. Yours sounds like it has power because the mode light is on.

Eventually I had to call out an Allison tech. He had a spare computer and shift pad. substituting them for mine just confirmed that the shift pad was not getting power. That led him to look for the broken wire. The tools the tech had for this situation were a test plug and a lap top PC. He hooked up the test plug at one end of the harness and the PC to the other end and was able to check continuity on each wire.

You and I do not have that capability. While it was expensive ($598.00) it was worth every penny because we were dead in the water.

You may get lucky and find the problem in the Vehicle Interface Module (VIM) which has one or two fuses that are easily checked and some relays that you can swap around thus changing or moving the symptoms.

I looked and found used and new ECM/TCM's at various prices (expensive). I had difficulty determining if the ones for sale were compatible with my transmission and shift pad. There have been changes over the years to these components. The Allison dealer I used (W.W. Williams) was very interested in knowing serial numbers and even asked for pictures of the TCM and shift pad so that they could bring the appropriate ones out on the service call.

Don't know about rebuilt. And, yes, I believe an Allison shop can tell if your ECM/TCM is good or bad.

Good luck. Let us know what you find out.

FWIW
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Old 05-29-2016, 09:45 AM   #3
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Thanks Dave--great response. As always seems to be the case, my symptoms are never quite the same as someone else's. I am blessed with an extensive "help network" of trusted owners of my brand on IRV2. While this sort of thing has happened to other owners a time or two, it was usually one of the fuses in the back bay--but not this time--as best I can diagnose.


Will need to wait until Tuesday to contact local Allison shop--in the mean time, rig is positioned outside the storage barn--this could of been so much worse if it had failed on the road--counting my blessings. Am hoping to pull ECM and have it bench tested--next step is finding a mobile Allison tech to visit coach as towing is a LAST resort. Went world-wide on the web hoping someone else had had a "similar" issue and could tell me I was missing something obvious--probably not.


PS--ECM link thru VIM is also a possibility--the troubleshooting link you provided will be a great primer for me.....


Thanks again for your insights....dean
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Old 05-30-2016, 06:18 PM   #4
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I had a similar situation happen to me in 2013. Initially the front dash lit up like a Christmas tree and the Allison pad had odd shapes on it. Then it all went blank. Checked everything I could and finally called the local Allison repair shop, they would not send tech had to have it towed.

Ultimately replaced the ECM for the transmission at a cost of +$3K. I was out of town and this was the fastest option to get the coach going as my wife had a trip planned.

Here is a possible source to get your touch pad or ECM rebuilt
Transmission Instruments
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Old 05-30-2016, 06:29 PM   #5
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Quote:
Originally Posted by jacwjames View Post
I had a similar situation happen to me in 2013. Initially the front dash lit up like a Christmas tree and the Allison pad had odd shapes on it. Then it all went blank. Checked everything I could and finally called the local Allison repair shop, they would not send tech had to have it towed.

Ultimately replaced the ECM for the transmission at a cost of +$3K. I was out of town and this was the fastest option to get the coach going as my wife had a trip planned.

Here is a possible source to get your touch pad or ECM rebuilt
Transmission Instruments
Check out their http://www.transmissioninstruments.c...eshooting.html also. We figured out what was wrong with ours with it. You can call them and Johnny is very helpful. If you follow the instructions you may be able to figure it out. Do make up the test light. A corroded connection may read 12V but still not work. English is his second language so read it carefully.

BTW an Allison tech told me it is almost never the shifter unless it has been repeatedly rained on or something.

Our problem turned out to be corroded wires coming from the VIM and really had not much to do with the transmission.
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Old 05-30-2016, 07:07 PM   #6
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Thanks everyone--initial input from Dave put me on to Transmission Instruments in Flower Mound Texas. Talked to them today--followed troubleshooting protocol and it appears to be a shifter keypad issue--I hope. Both the CPU and the keypad are removed, boxed up, and will be on their way to TI in the morning....will report back on what they find out for me.....
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