No start; dash indicates trans is in D

[BB69]

I have a 2009 IC with a Maxxforce DT 210HP engine and Allison 2500PTS transmission.

When I bought this (at auction) it has the same symptoms I'm seeing now. When I turn the key on, the dash comes alive and gives two warnings:

*Electrical fault
*Engine warn
Gear position shows as D (this bus doesn't have park, just neutral)

I crawled under the bus and realized the TCU was completely missing. I ordered a replacement, installed it, and the bus started immediately. I yard drove it many times over 4 months or so. That last time I drove it, I turned it off, tried to restart a few minutes later, and it won't start. The symptoms are identical to when the TCU was missing.

I put another TCU in it, and this time, no change. Based on the dash still showing it as in D, I'm suspecting a neutral safety switch. That switch is internal to this transmission as it's a 4th gen unit.

What is the diagnostic procedure for determining if the neutral safety switch isn't working?

What other causes should I be looking at?

Thanks
Ken

[ewo1]

Originally Posted by BB69

I have a 2009 IC with a Maxxforce DT 210HP engine and Allison 2500PTS transmission.

When I bought this (at auction) it has the same symptoms I'm seeing now. When I turn the key on, the dash comes alive and gives two warnings:

*Electrical fault
*Engine warn
Gear position shows as D (this bus doesn't have park, just neutral)

I crawled under the bus and realized the TCU was completely missing. I ordered a replacement, installed it, and the bus started immediately. I yard drove it many times over 4 months or so. That last time I drove it, I turned it off, tried to restart a few minutes later, and it won't start. The symptoms are identical to when the TCU was missing.

I put another TCU in it, and this time, no change. Based on the dash still showing it as in D, I'm suspecting a neutral safety switch. That switch is internal to this transmission as it's a 4th gen unit.

What is the diagnostic procedure for determining if the neutral safety switch isn't working?

What other causes should I be looking at?

Thanks
Ken

Allison 2000 Wiring diagram attached:

[BB69]

Originally Posted by ewo1

Allison 2000 Wiring diagram attached:

Thanks for posting those, but they are for a transmissions with the external neutral switch. My unit has an internal switch.

I'm guessing the function doesn't change much, so this at least gives me an idea what the switch really does.

[BB69]

I found this PDF online which shows the wiring for the 4th gen transmission. It includes detailed information on the neutral switch (called a mode switch).

https://www.atsg.us/atsg/skin/fronte...o_2015_PPT.pdf

[Booyah45828]

Step 1 is verifying the shifter actuates the lever on the trans.
Step 2 would be to use a scan tool and see what the computer sees when changing shifter positions.

NSBU switch is a possibility. Typically it'd show a range inhibit alarm as well. When they stuck them internal, the reliability issues they had with them when they were external nearly disappeared.

The shifter cable could have broken, or it could be misadjusted causing your issue. I wouldn't just start throwing parts at it, but it sounds like you've already done that with another tcm. So why not?

[Sp6saz]

Maybe the part you bought has a dirty connection or the part you bought has failed and you had found the problem but it's back.

[BB69]

I had to take some time away from the bus, but I'm back at it. Can you confirm where the diagnostic port is on this bus? From my reading it should be under the dash, by the driver's knee. I have several of the plastic bezels removed from around the steering column, and I still don't see the connector?

Thanks
Ken

[BB69]

I found the connector, under the dash closer to the middle of the bus. Basically, behind the radio.

[BB69]

From the dash, the bus has the following 4 codes:

SPN: 2392
FMI: 5
SA:33
OC: 1
CONN/PIN: 1601E4

SPN: 2003
FMI: 9
OC: 42
SA: 23

SPN: 8321
FMI: 7
OC: 0
SA: 0

SPN: 168
FMI: 4
OC: 0
SA: 0


It looks like the 2003 code is "23 2003 Source Address 3 9 Loss of data link from the
Transmission Controller" caused by an abnormal update rate. This suggests to me a problem with the TCM or power to the TCM. Does that seem right?

[ewo1]

Originally Posted by BB69

I found this PDF online which shows the wiring for the 4th gen transmission. It includes detailed information on the neutral switch (called a mode switch).

https://www.atsg.us/atsg/skin/fronte...o_2015_PPT.pdf

I found these Allison 4 gen mechanics tips doc.
Not sure if it has what you need, hopefully it provides some sort of good info.

http://www.hill-family.us/serrano/Ma...HANICSTIPS.pdf

Allison Gen 4 wiring harness parts catalog - might provide wiring insight?

https://www.stclairtech.com/docs/SCTCatalog2019.pdf


Mother load!
Allison trouble shooting manuals - free !

http://www.taurusfleetservices.com/i...ooting-manuals

I’m not a mechanic so I can’t help much. I’m learning as I go along and try to help out!

[sportyrick]

I have seen that the power to Allison transmissions is from a cable bolted directly to your starter. Have you been monkeying around in the starter/battery area? A friend of mine would take his batteries out for winter and re-install for race season. One year he had a problem with the ECM on his Freightliner and when he had a technician show up the cause was he inadvertently dropped the ECM cable behind the frame out of site. Hooked the cable back to his batteries and all was well. A several hundred dollar education.

[Sp6saz]

Originally Posted by sportyrick

I have seen that the power to Allison transmissions is from a cable bolted directly to your starter. Have you been monkeying around in the starter/battery area? A friend of mine would take his batteries out for winter and re-install for race season. One year he had a problem with the ECM on his Freightliner and when he had a technician show up the cause was he inadvertently dropped the ECM cable behind the frame out of site. Hooked the cable back to his batteries and all was well. A several hundred dollar education.

Ouch... that's how I learn a lot of times. I usually tell myself I saved so much in the past when I did it right that is ok and I needed all those new parts anyways ha ha.

[BB69]

Originally Posted by sportyrick

I have seen that the power to Allison transmissions is from a cable bolted directly to your starter. Have you been monkeying around in the starter/battery area? A friend of mine would take his batteries out for winter and re-install for race season. One year he had a problem with the ECM on his Freightliner and when he had a technician show up the cause was he inadvertently dropped the ECM cable behind the frame out of site. Hooked the cable back to his batteries and all was well. A several hundred dollar education.

I will look. I haven't been playing with anything. When this problem started, I had been driving the bus. Parked it, and tried to start again 30 minutes later. No go. With the two codes, it seems power related, so I will start with the cables. I bought the bus at auction, so it was probably sitting for at least a year.

[ewo1]

Originally Posted by BB69

I will look. I haven't been playing with anything. When this problem started, I had been driving the bus. Parked it, and tried to start again 30 minutes later. No go. With the two codes, it seems power related, so I will start with the cables. I bought the bus at auction, so it was probably sitting for at least a year.

Reading this thread has brought me bad luck. Got in my bus today, after it sitting for 3 weeks, starts right up but won’t go into gear!

When I press D or R on the push pad I get snake eyes and the check trans light comes on!

When I try to enter diagnostic modes on the push pad by pressing both the up and down arrows, once, at the same times…nothing happens.

This by the way is the method to check you trans fluid level on an MD3060 tranny. Can’t even do that !

Now I got to figure out…Why …why????