TCM to ECU communication issues t444e/Allison 2000 (2024)

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TCM to ECU communication issues t444e/Allison 2000 (2)01-04-2023, 06:15 PM#1

Flipmode

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Join Date: Nov 2019

Location: Palm Beach, FL

Posts: 63

Year: 2003

Coachwork: AmTran

Chassis: International

Engine: T444E

Rated Cap: 48 passenger

TCM to ECU communication issues t444e/Allison 2000

Hi Guys, I wanted to see if anyone had some insight on troubleshooting my issues that are limiting the mobility of my bus. It’s a 2004 International T444e with Allison 2000 series trans.

Currently the bus starts and runs normal except the check trans and shift inhibit lights are blinking almost constantly. When I shift it into reverse(and when it first happened: in any forward gear as well) the range inhibit light turns on solid and the trans is pretty much in neutral.

This problem happened after I pulled the gauge cluster off and resoldered the plug connections. My gauges had been intermittently having issues until recently when they stopped working altogether which prompted me to do the repair. I have since tried to run the bus with the dash disconnected and bluefire running but the trans issue persisted.

Running my bluefire module I get a SPN 2003 FMI 31 code in their program. 2003 31 is what I can found online to be a bad communication issue between the TCM and ECM. I’m getting only one active code and 3 inactive codes from the self test diagnostics. Two inactive codes are ecm issues but none of them are transmission codes so not sure if I can diagnose without Allison DOC computer. Also, my trans temp reading on the bluefire was reading over 300 degrees and that right at startup when everything is cold.

Active code:
155: 171 0 3 Air Inlet Temperature Signal Out of Range HIGH IAT

Inactive codes:
222: 0 247 2 Brake Switch Circuit Fault BRAKE

344: 0 34 29 Exhaust Back Pressure Above spec. when engine off or being cranked EBP

113: 168 0 4 Electrical System B+ Voltage Out of Range LOW ECM_PWR

626: 0 254 8 Unexpected reset fault ECM_PWR

My trans guy for OBD2 stuff says he doesn’t have the stuff for the J1939 system but pointed me to check the main trans plug by the tail shaft. He said check for oil in the plug as that can cause shorts in those plugs. I did find mine to be wet with oil so I cleaned out with brake cleaner then compressed air (two different times) with no change to the shift inhibit issues.

I pulled the TCM and checked the two plugs on it for pin or corrosion issues but they were surprisingly clean. I found and checked the 10amp fuse to the TCM which good. Battery voltage is above 12.6v at rest and running I think the system is around 13.5v. I inspected the round bulkhead plug but it atleast looked clean.

I’ve been looking the different International and Allison pdfs that EWO1 posted but haven’t fully comprehended that material and whether I should be focusing troubleshooting the ecm or the TCM. I realize the answer may be obvious with the information I have but at the moment it seems a little overwhelming to figure out what tangent to pursue next. If anyone has some pointers for me to try to troubleshoot next it would be appreciated.

At this point I’m reluctant to even try to move the bus without figuring out what’s up with the trans. A shop I called said I needed to have it towed to them as they don’t do mobile work. I’m not opposed to getting it towed to a professional but am actually enjoying getting more familiar with the bus’s electrical system and feel it’s a worthwhile time investment even if I can’t fix it myself. The bus is comfortably parked on the side of my house for now but it typically is a 3 point turn situation to pull it out so it would be great if I can get it to move forward and reverse under its own power. Thanks for any insight or direction into troubleshooting you can provide. Phillip

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TCM to ECU communication issues t444e/Allison 2000 (6)
TCM to ECU communication issues t444e/Allison 2000 (8)01-04-2023, 06:53 PM#2

cadillackid

Bus Geek

Join Date: May 2009

Location: Columbus Ohio

Posts: 18,917

Year: 1991

Coachwork: Carpenter

Chassis: International 3800

Engine: DTA360 / MT643

Rated Cap: 7 Row Handicap

the key factor here.. your trrans is in neutral? or do you have reverse and one forward gear? (3rd usually)..

if you cant get any forward motion out of an allison 2000 then you need to start internally to the trans..

on mine if I yank the J1939 loose, I get a check trans light and then the trans fails to lock up but will still run through its gears...

if I knock the power out to my TCM then I get reverse-neutral-and one forward gear (3) when the T handle is in 'D'

it almost sounds to me like your TCM isnt even booting up fully.. although you do get an inhibit and a check trans light so it at least partially comes online... could be 1 of the 2 power feeds to it is defunct.. if the BAT+ feed is not there then the TCM will only minimally come up and wont communicate or control the trans

TCM to ECU communication issues t444e/Allison 2000 (9)
TCM to ECU communication issues t444e/Allison 2000 (11)01-04-2023, 07:54 PM#3

Flipmode

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Join Date: Nov 2019

Location: Palm Beach, FL

Posts: 63

Year: 2003

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Chassis: International

Engine: T444E

Rated Cap: 48 passenger

Currently the trans goes into gear when I put it in drive but pretty much stays in neutral when shifted in reverse. When I initially had the problem it was in neutral when shifting to a forward gear as well but somehow that part of the issue disappeared. Some of the first things I tried was checking and disconnecting the batteries as well as charging them to make sure they were fully charged.

My bus is parked next to my house where I have to pull it around a tight corner to get it out which requires me to use reverse to reposition halfway through to not scrape my house. I haven’t attempted to actually drive it with the hope of being able to atleast get reverse to function as I’m sure i could manually get the bus to go backwards but not looking forward to it if I don’t have to.

So just tried unhooking the 1939 connector at the transmission and it did indeed allow it to go into reverse.TCM to ECU communication issues t444e/Allison 2000 (13)

I guess I’ll look into testing the power feeds including Bat+ feed on the TCM and go from there.

As far as unhooking the j1939 system, what is the effects of moving the bus while the system is unhooked? I don’t know automatic transmissions real well so just want to make sure it’s not going to be detrimental to drive it like that.

Thank you for your insight ChrisTCM to ECU communication issues t444e/Allison 2000 (14)

TCM to ECU communication issues t444e/Allison 2000 (15)
TCM to ECU communication issues t444e/Allison 2000 (17)01-05-2023, 10:02 PM#4

Flipmode

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Join Date: Nov 2019

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Rated Cap: 48 passenger

So I tested power and ground to the pins in the gray plug. Both grounds check good(pins 101 and 105), battery +(103) good, and ignition on + (102 and 104) was good. I looked close at the pins and everything looked clean, shiny, and straight alignment.

Initial key of voltage was 12.69v. When testing both ignition pins with the key on, the voltage dropped below 12v for several seconds. Then I heard a relay I believe on the firewall cycle and the voltage came up to 12.39v and stayed as the brake booster pump was running since initial key on. Any thoughts on that initial key on voltage drop and would sub 12v cause any computers to act up? Just trying to grab low hanging fruit here…

I guess now that I can get it to reverse I’ll try to take the bus around the block and see what the gear situation is. That will atleast let me find out if it’ll drive to the shop which is about 6 miles away.

TCM to ECU communication issues t444e/Allison 2000 (19)
TCM to ECU communication issues t444e/Allison 2000 (21)01-06-2023, 08:36 PM#5

cadillackid

Bus Geek

Join Date: May 2009

Location: Columbus Ohio

Posts: 18,917

Year: 1991

Coachwork: Carpenter

Chassis: International 3800

Engine: DTA360 / MT643

Rated Cap: 7 Row Handicap

your voltage drops down becasuse the glowplugs kick on with the key on, then they eventually shut off.. I think something like 30 seconds after thwe wait-to-start light goes off if you dont start the engine.. so then your voltage would pop back up and you probably hear the glowplug relay release..

TCM to ECU communication issues t444e/Allison 2000 (22)
TCM to ECU communication issues t444e/Allison 2000 (24)01-09-2023, 05:25 AM#6

Diverdude0075

Bus Nut

Join Date: Aug 2020

Location: East TN

Posts: 303

Year: 1999

Chassis: International

Engine: T444E

Your trans worked perfectly before repairing the cluster?

TCM to ECU communication issues t444e/Allison 2000 (25)
TCM to ECU communication issues t444e/Allison 2000 (27)01-09-2023, 09:48 AM#7

Flipmode

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Join Date: Nov 2019

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Year: 2003

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Engine: T444E

Rated Cap: 48 passenger

I’ve only been driving the bus every other month or so lately but yes, it’s been working fine the last few times I’ve had it out. A year or so ago I had a few hiccups where the Speedo wasn’t matching the speed and it did go into limp mode but it disappeared when I turned it off and restarted it but didn’t reappear.

I took the bus out on Saturday around the block to see how the trans would drive. With everything plugged in and the trans light flashing, it was stuck in first gear and wouldn’t go in reverse. Driving around the block, the trans was making some sketchy noises that sounded like clutches were trying to lock up or solenoids were shifting…. Hard to describe but it was a light clunking noise that was slightly detectable in feel.

I didn’t realize when I first got the bus to go in reverse with Cadillackid’s recommendation of disconnecting the communication wire, I also had the fuse remove to the TCM. So just by disconnecting the J1939 plug I still can’t get into reverse. I have to disconnect power to the TCM to get reverse.

After driving with everything plugged in, I then pulled the power to the TCM and took it around the block. I think it was stuck in second gear but was hard to gauge as my Speedo wasn’t working to compare rpm’s to. It ran good and had none of the “clunking” noises it had with the TCM powered up. So at this point I’m realizing I need to get the Tranny codes read so I’m calling around to see if I can get a mechanic house call so I atleast can judge if it’s something I can pursue further or if I need professional help… lol

TCM to ECU communication issues t444e/Allison 2000 (29)
TCM to ECU communication issues t444e/Allison 2000 (31)01-09-2023, 02:58 PM#8

cadillackid

Bus Geek

Join Date: May 2009

Location: Columbus Ohio

Posts: 18,917

Year: 1991

Coachwork: Carpenter

Chassis: International 3800

Engine: DTA360 / MT643

Rated Cap: 7 Row Handicap

I was just in florida... I almost went to Stuart but had no reason as wasnt much going on at our office so I stayed in orlando.. I shoulda read the skoolie net forum more.. I had my Nexiq and PC / allison DOC with me too..

Limp mode gives you reverse and 3rd.. whats interesting is no gears with the TCM connected... almost sounds like an Inhibit mode getting enabled.. is there a possibility that a wire cut during conversion for say a parking brake, wheelchair lift, etc got grounded?

inhibit modes are common on some school busses, esp wheelchair busses ... the trans isnt allowed to go into gear when the lift is deployed, and in some cases the air park brake applied.. its really easy to miss these wires when cutting things out for conversion and cause an issue...

TCM to ECU communication issues t444e/Allison 2000 (32)
TCM to ECU communication issues t444e/Allison 2000 (34)01-09-2023, 09:56 PM#9

Flipmode

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Join Date: Nov 2019

Location: Palm Beach, FL

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Quote:

Originally Posted by cadillackid

I was just in florida... I almost went to Stuart but had no reason as wasnt much going on at our office so I stayed in orlando.. I shoulda read the skoolie net forum more.. I had my Nexiq and PC / allison DOC with me too..

Limp mode gives you reverse and 3rd.. whats interesting is no gears with the TCM connected... almost sounds like an Inhibit mode getting enabled.. is there a possibility that a wire cut during conversion for say a parking brake, wheelchair lift, etc got grounded?

inhibit modes are common on some school busses, esp wheelchair busses ... the trans isnt allowed to go into gear when the lift is deployed, and in some cases the air park brake applied.. its really easy to miss these wires when cutting things out for conversion and cause an issue...

I’m about 45 min south of Stuart so that would have been a big detour from Orlando but I appreciate the thought.

The inhibit mode angle hadn’t been really on my radar but it is probably a tangent I need to explore. As far as conversion type stuff I don’t believe I’ve done much mods or removal of the electrical in atleast a year besides the dash fix of resoldering the pins. Never had a handicap lift and I deleted all the Exit door/hatch sensors a few years ago by just closing the circuit at each point. I’ll go a check all those points just to be sure.

The bus is holding an inactive code 222 which I believe is Brake Switch Circuit Fault. I’ll try to get into that part tomorrow but I’m not seeing an obvious circuit on the Allison 2000 wiring schematic. Is it part of the Neutral start backup switch?

I got a couple of numbers for mobile mechanics to call tomorrow so hopefully I can find one to see what the TCM is saying. Im actually kinda enjoying this troubleshooting process for getting me more familiar with the electronic side of the drivetrain but with the multiple variables at play I’m hoping reading the TCM will get me in the right direction. I’m just thankful the bus is having these issues on the side of my house and not out on the road…

TCM to ECU communication issues t444e/Allison 2000 (37)
TCM to ECU communication issues t444e/Allison 2000 (39)01-10-2023, 03:57 AM#10

Diverdude0075

Bus Nut

Join Date: Aug 2020

Location: East TN

Posts: 303

Year: 1999

Chassis: International

Engine: T444E

Sounds like a cut or loose wire to me. When I did my transmission swap my bus stayed in limp mode until I figured out a missing wire that had to be connected. In your case it may be a cut wire. I had reverse though and either 2nd or 3rd gear. Once I connected that wire she ran perfectly, just in time to move 1500 miles away!!

Perhaps take your cluster back off and look for damaged/cut or a loose wire? Look for something around your gear selector too.

TCM to ECU communication issues t444e/Allison 2000 (40)
TCM to ECU communication issues t444e/Allison 2000 (42)01-10-2023, 06:35 AM#11

cadillackid

Bus Geek

Join Date: May 2009

Location: Columbus Ohio

Posts: 18,917

Year: 1991

Coachwork: Carpenter

Chassis: International 3800

Engine: DTA360 / MT643

Rated Cap: 7 Row Handicap

the door / window / hatch sensors shouldnt be a reason for shift inhibit.. they will just make the bus buzz.. a no-child left behind system typically affects the engine start circuit (you cant start the bus or sometimes turn it off till you clear it).. but ive never seen one that affected the trans so you should be OK there.. the lift was the main thing if it had one.

the bnrake switch code is pretty common.. there are 2 brake switches and sometimes they get out of adjustment.. if the computer sees too many times where one switch activates and the other doesnt, it tosses a code. it will make your cruise control not work for the duration of the key cycle.. it does not turn on the WARN light.. trans will work fine.

the main inputs you will see to the transmission are for power and ground, the speed send (goes to your speedo), and the J1939, and the netutral safety, reverse lights circuit..

inhibit is one on my diagram which showed up as a dotted line and "optional".. looking at my diagram i pulled for I think a 2004 bus...

its possible navistar wired an inhibit pin out into the harness and then capped it off.. ive seen that done more than once with circuits on navistar for optional components. but id expect the circuit to be disabled in the trans TCM at that point.

allison typically put the inhibit pin in the list of 'CMC' Customer-Modifiable-Constants where a body-builder could use allison DOC even at its lowest fleet-level to turn it on or off if say a lift was added (or in the case of trucks like Bucket trucks and Boom trucks, you dont want the vehicle to move when the extra equipment is deployed)..

I typically make several trips to florida over the winters.. although this winter its looking more like i will be in Texas as we have 3 really big jobs to do down there.. so I may not make another trip for awhile.. id love to get down at least to say hi at the swarm.. as Ive only ever attended the original swarm in 2018.. each year thereafter ive been busy and not able..

-Christopher

TCM to ECU communication issues t444e/Allison 2000 (43)
TCM to ECU communication issues t444e/Allison 2000 (45)01-10-2023, 07:05 AM#12

ewo1

Bus Crazy


Join Date: May 2015

Location: Central Tx.

Posts: 2,026

Year: 1999

Chassis: Amtran / International

Engine: DT466E HT 250HP - Md3060

Check trans light- terminating reistors

A bus I helped build was having weird intermittent trans issues, one was the check trans light turning on and off at random and when it did it was sometimes go into limp mode.

It turned out to be the weirdest problem but one of the easiest to fix.

Here is something that is almost never talked about or looked at…..

On the j1939 data cable you will find a pair (2) wires that are yellow/green.
Those wires are terminated with 120 ohm 1/4 watt resistors.
Back in the radio shack days They would cost you about a dollar each.

I am not personally aware exactly where these resistors are located but from what I can read they should be at either end of that data cable.

From a troubleshooting standpoint I would for sure check these out and eliminate if this is or is not a condition causing your situation.

Here is an interesting write up and the subject.

TCM to ECU communication issues t444e/Allison 2000 (47)
TCM to ECU communication issues t444e/Allison 2000 (49)01-10-2023, 07:08 AM#13

cadillackid

Bus Geek

Join Date: May 2009

Location: Columbus Ohio

Posts: 18,917

Year: 1991

Coachwork: Carpenter

Chassis: International 3800

Engine: DTA360 / MT643

Rated Cap: 7 Row Handicap

Quote:

Originally Posted by ewo1

A bus I helped build was having weird intermittent trans issues, one was the check trans light turning on and off at random and when it did it was sometimes go into limp mode.

It turned out to be the weirdest problem but one of the easiest to fix.

Here is something that is almost never talked about or looked at…..

On the j1939 data cable you will find a pair (2) wires that are yellow/green.
Those wires are terminated with 120 ohm 1/4 watt resistors.
Back in the radio shack days Thayer would cost you about a dollar each.

I am not personall aware exactly where these resistors are located but from what I can read they should be at either end of that data cable.

From a troubleshooting standpoint I would for sure check these out and eliminate if this is or is not a condition causing your situation.

Here is an interesting write up and the subject.

they are "supposed" to be internal to the computers... I dont have any externall resistors installed on my J1939 data bus.. the data link schematics from navistar dont show any.. I hooked all 3 wires up on my J1939 9as the factory does).. the black is a reference ground so there is not floating of the voltages along the CAN.. essentially for ease of conversation the J1939 CAN runs on a similar to RS485 comms link..

this doenst however mean that the internal term resistors havent been blown which could cause erratic comms..

TCM to ECU communication issues t444e/Allison 2000 (51)
TCM to ECU communication issues t444e/Allison 2000 (53)01-10-2023, 07:10 AM#14

ewo1

Bus Crazy


Join Date: May 2015

Location: Central Tx.

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Chassis: Amtran / International

Engine: DT466E HT 250HP - Md3060

More good info….

Source

In the allison manual U2104=U0073 and U2105=U0100 bothe codes point to the J1939 data communications link between engine and trans. If you can read ecm data from the trans the code is inactive. Disconnect the batteries and check the ohms across the nine pin diagnostic connector @ pins c to d 60ohms c to e open and d to e open also check c&d to ground should be open as well.
code is set on these wires yellow+ and dk green- and wire shield being grounded or open,also commonly known as the J1939 Can backbone harness. There is a 120 ohm resistor at each end of the harness, if you have more than 60 ohms on the pins one of these may be bad but most likely there is a wire rubbed through or rubbing on something causing the problem.

Diagram from Mouser electronics…

TCM to ECU communication issues t444e/Allison 2000 (55)
TCM to ECU communication issues t444e/Allison 2000 (57)01-10-2023, 09:41 AM#15

Flipmode

Mini-Skoolie


Join Date: Nov 2019

Location: Palm Beach, FL

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Year: 2003

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Chassis: International

Engine: T444E

Rated Cap: 48 passenger

I did an ohm check the other night and found all to be in range. I found a pretty straightforward troubleshooting guide online by Terex. I have my results written down at home but the ohm values were in spec and my voltages were right there. Definitely an easy test to perform.

I believe the resistors in my j1939 harness are in the 3 way junctions. The third output appears to have a plug which I believe is the resistor module. I didn’t bother going that far after the backbone seemed to test out ok.

Here’s the link to the Terex j1939 testing:

https://www.terex.com/docs/libraries...sn=ef66cbab_13

TCM to ECU communication issues t444e/Allison 2000 (59)
TCM to ECU communication issues t444e/Allison 2000 (61)01-10-2023, 10:52 AM#16

Flipmode

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Join Date: Nov 2019

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Quote:

Originally Posted by Flipmode

I did an ohm check the other night and found all to be in range. I found a pretty straightforward troubleshooting guide online for a J1939 by Terex. I have my results written down at home but the ohm values were in spec and my voltages were right there. Definitely an easy test to perform.

I believe the resistors in my j1939 harness are in the 3 way junctions. The third output appears to have a plug which I believe is the resistor module. I didn’t bother going that far after the backbone seemed to test out ok.

Here’s the link to the Terex j1939 testing:

https://www.terex.com/docs/libraries...sn=ef66cbab_13

*just thinking about it, I may be misguided by using the troubleshooting guide from a totally different system but it seemed to be similar to the J1939 system on the bus so im assuming that they're similar enough for testing purposes...

TCM to ECU communication issues t444e/Allison 2000 (64)
TCM to ECU communication issues t444e/Allison 2000 (66)01-11-2023, 12:44 PM#17

SeekingDiscovery

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I am having a similar issue. I have SPN 2003 FMI 31 and SPN 2033 FMI 14. The bus shut down the last time I drove around the block when I came to a stop. It fired right back up and I got back safely but also felt like it had trouble shifting around the 35mph mark. The warn engine light comes on and off.

I have checked fuses, and relays, put in new start batteries, checked wire connections for oil, and tried to clean everything up but it still appears to have the codes and similar issues.

Any ideas?

TCM to ECU communication issues t444e/Allison 2000 (68)
TCM to ECU communication issues t444e/Allison 2000 (70)01-11-2023, 08:23 PM#18

Flipmode

Mini-Skoolie


Join Date: Nov 2019

Location: Palm Beach, FL

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Year: 2003

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Engine: T444E

Rated Cap: 48 passenger

Quote:

Originally Posted by SeekingDiscovery

I am having a similar issue. I have SPN 2003 FMI 31 and SPN 2033 FMI 14. The bus shut down the last time I drove around the block when I came to a stop. It fired right back up and I got back safely but also felt like it had trouble shifting around the 35mph mark. The warn engine light comes on and off.

I have checked fuses, and relays, put in new start batteries, checked wire connections for oil, and tried to clean everything up but it still appears to have the codes and similar issues.

Any ideas?

Nothing obvious yet. I only had the 2003-31 so not familiar with the 2033-14. I got a mechanic scheduled to come out Sunday in his off time to read TCM codes so I’ll keep this thread updated then with results.

TCM to ECU communication issues t444e/Allison 2000 (73)
TCM to ECU communication issues t444e/Allison 2000 (75)01-12-2023, 06:51 AM#19

cadillackid

Bus Geek

Join Date: May 2009

Location: Columbus Ohio

Posts: 18,917

Year: 1991

Coachwork: Carpenter

Chassis: International 3800

Engine: DTA360 / MT643

Rated Cap: 7 Row Handicap

apparently the forum lost my last post... so i played a little before I tore my bus in pieces.. interesting thing is on my T444E running an 04 ECM, I pulled the J1939 plug off of my trans to ECM connector.. my check-trans light came on, my ECM didnt register a code... (maybe I didnt wait long enough).. my TCM registered that it had lost J1939 comms..

the trans operated in all of its gears (at least 1-4 i didnt drive far).. and reverse.. it however never locked up the converter.. reading the data realtime as i drove, it still reigstered a pseudo throttle position in the TCM.. appeared based on the amount of difference in engine RPM vs inpiut shaft RPM...

it shifted pretty terrible...

when I plugged the connector back in and restarted the bus, the check trans light just did its normal flash on for a second then off.. asnd the bus drove normally... trans was back to shifting solidly..

one of the things to have the machanic check when he comes out is not only error codes in your TCM.. but also look for inhibit modes enabled.. and of one shows up, get the input number.. (allison DOC will show the input triggering the inhibit)..

if an inhibit is enabled and is simply an external wire.. his DOC may allow him to just disable the input which would prevent the trans from going into inhibit via this "wire" or input number..

if there are error codes for say stuck solenoids and such (which will put a trans into inhibit) then you pretty much have to drop the pan anmd investigate..

hopefully some good info is learned from his visit!!.

I looked up my trans and the TCM im running has inhibit inputs programmed into it , one is listed as a 4WD input, another as just a general, another as a 4WD lo... all of them are turned on even though i dont think the pins are even wired on my TCM connector...

TCM to ECU communication issues t444e/Allison 2000 (76)
TCM to ECU communication issues t444e/Allison 2000 (78)01-12-2023, 07:59 AM#20

ewo1

Bus Crazy


Join Date: May 2015

Location: Central Tx.

Posts: 2,026

Year: 1999

Chassis: Amtran / International

Engine: DT466E HT 250HP - Md3060

Quote:

Originally Posted by Flipmode

I did an ohm check the other night and found all to be in range. I found a pretty straightforward troubleshooting guide online by Terex. I have my results written down at home but the ohm values were in spec and my voltages were right there. Definitely an easy test to perform.

I believe the resistors in my j1939 harness are in the 3 way junctions. The third output appears to have a plug which I believe is the resistor module. I didn’t bother going that far after the backbone seemed to test out ok.

Here’s the link to the Terex j1939 testing:

https://www.terex.com/docs/libraries...sn=ef66cbab_13

Out or curiosity, what exactly were the ohm ( resistance ) values you measured?

Also, I have found, from lots of experience, if you want to best test/measure the integrity of a wire / connection it is best to use an alanlog test meter.

Digital meters can absorb “noise” on a line and still give you a qualified reading but in reality any noise on a line is caused by a loose or poor connection. That is, Noise that is not introduced by induction but noise caused by loose connections.

Earlier Diverdude0075 posted about loose or cut wires. I would go back and triple check you cluster repair work and check the integrity of the wiring with an analog meter….just to make absolutely sure your not missing something very simple.

From my experience, twice now I had md3060 issues that were caused by bad wiring/ connections.

My friends bus is an Amtran, Dt466e, Allison 2000. Their issue we thought was the TCM, turned out to be the resistors.

Oh yeah, the resistors should read between 55 and 65 ohms. Anything else and you got an issue to address.

There are 2 120 ohm resistors in parallel and that should give you a 60 ohm reading.

Keep us posted!

TCM to ECU communication issues t444e/Allison 2000 (81)
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TCM to ECU communication issues t444e/Allison 2000 (2024)

FAQs

What is the problem with the Allison TCM transmission? ›

Allison TCM Failure Symptoms

The most notable symptom of a failing Allison A50 T14 TCM is hard shifting. This can cause havoc on your transmission's internal components and even your driveshaft U-joints. You may also end up in limp home mode” where your transmission sticks itself in third gear.

What does TCM stand for in Allison transmission? ›

The Transmission Control Module (TCM) of your Allison Automatic. monitors the transmission's electronic controls; and when a problem. condition is detected, it: – Restricts shifting. – Illuminates the CHECK TRANS* light on the instrument panel.

What can cause a TCM to lose communication? ›

A U0101 code occurs because the TCM is having a difficult time communicating with the rest of the car. That means the most common reasons for a U0101 code are very simple things, such as a faulty battery with voltage issues, damaged terminals, disconnected connectors, and damage to the ground connection.

What are the symptoms of a faulty TCM? ›

Signs of a Bad Transmission Control Module
  • Unpredictable shifting.
  • Trouble shifting into higher gear.
  • Trouble downshifting.
  • Getting stuck in the same gear.
  • Poor fuel economy.
  • Check engine light comes on.

Does the ECU control the TCM? ›

A transmission control unit (TCU), also known as a transmission control module (TCM), or a gearbox control unit (GCU), is a type of automotive ECU that is used to control electronic automatic transmissions.

What causes TCM malfunction? ›

The most likely reasons for failure include: Electrical issues. Electrical problems, such as damaged wiring, loose connections, or short circuits, can disrupt the communication between the TCM and sensors, leading to malfunctions. Overheating.

What is the problem with the TCM? ›

Common symptoms of bad TCM include difficulty shifting gears, erratic or harsh shifting, transmission slipping and transmission overheating. It also includes illuminated warning lights (such as the Check Engine Light or Transmission Warning Light) and transmission-related error codes.

What would cause a TCM to fail? ›

The most likely reasons for failure include: Electrical issues. Electrical problems, such as damaged wiring, loose connections, or short circuits, can disrupt the communication between the TCM and sensors, leading to malfunctions. Overheating.

Can you still drive with a faulty TCM? ›

It's never safe to drive with a faulty transmission control module because it causes your car to be extremely unpredictable when it comes to shifting gears. If you notice any of the signs listed above, you're going to want to get your vehicle to the shop immediately.

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