Bus # 9906

[ewo1]

For anyone interested in learning about Trans ID, what it represents, I attached the few pages of the manual that covers this topic.

What I found interesting is that the TCM will autolearn after 25 engine starts?

 

[skoontz]

Mine still started with the wrong TCM files loaded, and IIRC, the shift pad also blinked. it just would not go into gear. On mine, the wrong TCM came from an RV, and I assume an interlock was put into place to ensure slide ins or jacks were stowed.

To get it reprogrammed with 6th gear, your best bet may be to contact Charlie Ball on Facebook. Check the link I posted for more info on him. If the dealer reprograms the TCM, they won't be able to unlock 6th.

 

[ewo1]

Mine still started with the wrong TCM files loaded, and IIRC, the shift pad also blinked. it just would not go into gear. On mine, the wrong TCM came from an RV, and I assume an interlock was put into place to ensure slide ins or jacks were stowed.

To get it reprogrammed with 6th gear, your best bet may be to contact Charlie Ball on Facebook. Check the link I posted for more info on him. If the dealer reprograms the TCM, they won't be able to unlock 6th.

Thanks !
That some really sound advice! I think i’ll reach out to him.
How much was the programming?

 

[ewo1]

TCM Calibration

So I talked with Charlie Ball and got a sweetheart of a deal.
It seems that since I got the TCM from a like unit (engine/trans) I probably don't need to get it re-flashed but calibrated instead.

The donor bus probably had interlocks for wheelchair or e-door and I only need to get the TCM re-calibrated and turn off those interlock features which are causing the TCM to go into "Shift inhibit" mode.

The sweet deal...only $50 bucks, plus shipping both ways.
God I hope it's this simple!

 

[DeMac]

Disable Interlock @ TCM

So I talked with Charlie Ball and got a sweetheart of a deal.
It seems that since I got the TCM from a like unit (engine/trans) I probably don't need to get it re-flashed but calibrated instead.

The donor bus probably had interlocks for wheelchair or e-door and I only need to get the TCM re-calibrated and turn off those interlock features which are causing the TCM to go into "Shift inhibit" mode.

The sweet deal...only $50 bucks, plus shipping both ways.
God I hope it's this simple!

-----------------

I wonder if this⤴ would be an option for owners who've cut wires and have interlock troubles. $50 is a cheap interlock fix.

 

[ewo1]

So out of curiosity and wanting to learn more, I visited a local diesel shop today to enquire about disabling the "shift disable" function on my TCM. Talking with the mechanic, his explanation of things made me feel like "I" was wrong, that this could not be disabled via calibration changes but MUST be made via wiring harness modification. The sum total of the conversation made me feel that he was just lubing me up for a pricey repair bill. His rate was $125 an hour and he said it might take to or three hours...nice lube job indeed.

Well me being me, I didn't trust him one bit but it did make me think about what he said it being a wiring issue.

Well I opened up the Allison troubleshooting manual (TS3989EN) and on page 655 found some very interesting information regarding the I/O functions of the TCM.

This page shows that this just might be something very easy to do, snip 2 wires and tie them together???

Read the note that is in the wiring diagram ...about wire # 101 and 103 being tied together!


Take a look at the sheet I uploaded and tell me what you think?

I don't know if I have the correct wiring diagram but I don't see a "Range inhibit" wire/terminal or a "Signal return" wire either.

For anyone that wants to help decipher this, I also attached the Allison 3000, TID2 wiring diagram. (TS2973EN)

 

[ewo1]

GEN3 vs GEN4 TCU's Identification

So I think I just learned something really important.

To determine which TCU you have look at how many connectors that connect to it.

If it is only one connector, it is a GEN4, 80 pins.
The correct troubleshooting manual should be TS3989EN

If you have 3 connectors to the TCU then the correct troubleshooting manual should be TS2973EN.

I have been going crazy trying to figure out which two wires I need to splice together in order to disable shift inhibit and was looking at the wrong manual!


Disregard post #146, I got it wrong!

 

[ewo1]

Shift inhibit bypass-Gen3-Braake pedal input

Ok, sO i think I got this figured out.
GEN3 (3 connectors to TCM) use troubleshooting manual TS2973EN

Pages 190-192 will identify each wire and what the function of that wire is.

Page 352 has the circuit diagram for the SHIFT- INHIBIT- BRAKE PEDAL CIRCUIT.

TCU with the SHIFT INHIBIT circuit enabled must have wire 155 permanently connected to wire 161 if this function (shift Inhibit) is not being used.

The "V" (Gray) connector, v-11, green wire #155, General purpose input #1 gets connected to...

V31, Yellow wire, Digital return.

The corresponding pins are Pin/terminal 11 and Pin/Terminal 31 on the connector itself at the TCM.



Skoolie scholars, please take a look and tell me if this makes sense...


If this works, easy fix/work around for others changing TCMs who have the shift inhibit enabled!

TS2973EN-6.7MB, can't upload...
https://www.trucktransdiag.com/downloads/wtec3.pdf


Disregard post #146, I got it wrong!

 

[dbsoundman]

Ok, sO i think I got this figured out.
GEN3 (3 connectors to TCM) use troubleshooting manual TS2973EN

Pages 190-192 will identify each wire and what the function of that wire is.

Page 352 has the circuit diagram for the SHIFT- INHIBIT- BRAKE PEDAL CIRCUIT.

TCU with the SHIFT INHIBIT circuit enabled must have wire 155 permanently connected to wire 161 if this function (shift Inhibit) is not being used.

The "V" (Gray) connector, v-11, green wire #155, General purpose input #1 gets connected to...

V31, Yellow wire, Digital return.

The corresponding pins are Pin/terminal 11 and Pin/Terminal 31 on the connector itself at the TCM.



Skoolie scholars, please take a look and tell me if this makes sense...


If this works, easy fix/work around for others changing TCMs who have the shift inhibit enabled!

TS2973EN-6.7MB, can't upload...
https://www.trucktransdiag.com/downloads/wtec3.pdf


Disregard post #146, I got is wrong!

The way I'm reading this, you want an open circuit between the two pins to disable the shift inhibit (doors closed, ready to drive). When shift inhibit is active, your shift indicator goes dark. From what I've read so far your shift pad isn't going dark, it's flashing 6 right?

 

[ewo1]

The way I'm reading this, you want an open circuit between the two pins to disable the shift inhibit (doors closed, ready to drive). When shift inhibit is active, your shift indicator goes dark. From what I've read so far your shift pad isn't going dark, it's flashing 6 right?

The shift inhibit and open doors are 2 different circuits, I do not know if they work together or separately, that is a good question!

If your bus even has this function at all then, switch closes when you open the door(s) (wheelchair door maybe) sending power to the TCU which will then put your trans in neutral.

So if your bus does not have this function but your new TCM is enabled to put the tranny in neutral (donor bus had this feature) there are two ways you can disable this.
1) re-calibrate the TCU and turn off this feature in the TCU or..
2) make sure V13 stays open-no power applied (cut the wire?)

Note, this feature is for transit busses.


I am just learning this so I could be wrong.

My issue is the TCM not going into gear, "R" and "D" just blinks, brake shift inhibit?? I hope!

I posted the open door circuit for those folks who might run into this.

 

[dbsoundman]

Oh yeah. My bus will flash my selected drive gear if I don’t have my foot on the brake or if the check trans light is on (mine stays on for like a minute at startup).

Maybe you have a sensor issue?

 

[ewo1]

Sensor...maybe?

On my 2005 bus that I rebuilt the engine on, I got to apply the brake to get it into gear.

On the '99 bus (roof Raise) never had to apply the brake to get it in gear but that bus is a 5 speed and I'm changing the TCM from another bus that was a six speed so I'm guessing that the donor bus, like my 2005, needed to apply the brakes.

I'm gonna try doing the mod wiring this weekend to see it that solves my issue.

If it does...woo hoo!

 

[ewo1]

Success ! 6th gear enabled!

-----------------

I wonder if this⤴ would be an option for owners who've cut wires and have interlock troubles. $50 is a cheap interlock fix.

First, to answer your question, the shift interlock bypass at the TCM worked like a charm! So yes, quick easy interlock fix!

So I finally got under the bus and shorted pin 11 and 31 on the gray connector to the TCM.
I didn't cut any wires, just peeled back the insulation about 6 inches into the loom and twisted a short jumper wire to terminal 11 and 31.

(Note: wiring diagram says yellow and green wire but mine was Brown and green. just make sure your on the correct terminal positon, The gray connector is numbered on the inside.)

Started the bus and push pad display no longer blinking, went right into gear!

Took a 40 mile test drive and all went well!

70 MPH @ 1900 RPM!

WOO HOO!

 

[Kentucky Dreaming]

Took a 40 mile test drive and all went well!
70 MPH @ 1900 RPM!
WOO HOO!

Cool beans!!!!! :bow::bow: