Check Trans Light

[Busboyz]

Hey everyone new to the site but have a total of 4 skoolies .
I have a 2003 IC bus with a DT466E and a 2000 series transmission.
i have this bus gutted and all open so i used it for a media room a couple weeks ago on a family camp out i took two buses there and the IC was where the kids were hanging out. So over the weekend there were 12 kids in and out of the bus (some mine and some not mine) anyhow some were playing in the driver seat and pulling on the gear shiftier, when i drove the bus there it was fine now the Check Trans light is on and it is stuck in low gear 18 mph might i add. Wondering if there is some easy fix or will i have to have a mobile company come and hook up to the bus for a diagnostic.

Thanks in advance

[Native]

Sounds like your transmission is in "limp-along-mode". I have no idea how it got there nor how to "fix" it, other than disconnecting the battery for a day to let the computers (engine and transmission) reset.

[Busboyz]

so i unhooked the batterys on it for a few days now went back today and hooked everything up got in the seat to start it it started just fine but i still have the Check Trans light on the dash. i have looked at the transmission shiftier arm and it moves like it should and transmission fluid is up to where it should be as well

[Busboyz]

HELP!!!!
So i took my TCM off and had it tested the guys there were super helpful and said everything in the TCM seamed to be fine and advised me to check the OHMs resistance on the C and D pin in the Data link hook up it should be 60 OHMs im reading 78/88 OHMs.
Has anyone ever had this problem?

[cadillackid]

are the codes getting set indicating a J1939 communications fault? the ohm reading you are getting shouldnt take the link down.. if it was open on one or the other wires or shorted to ground then you'd have issues for sure..



a broken data link wont Limp the transmission it will run it in Non-lockup mode but you will have all the gears.. if it is Limped (usually 2nd or 3rd gear depending on the inhibit schedule in the TCM) if it is truly stick in first then id suspect a solenoid that has stuck on and wont release id have to look and see which shift solenoid operate in which gear.. its hard to tell without reading the fault codes
-Christopher

[Busboyz]

Yes the print out he gave me today says
SAE J1939-11 along with U0100 and Previously U2105

I had to drive it from where it went into limp mode and its Definitely stuck in low gear 18 mph is top speed i had to drive it 3 miles to my house.

The guys there told me to test the OHMs and if it wasnt 60 then to check the Termination Resisters.

After looking around and tracing some wires down i found a yellow wire that is pulled out of its connector and a green wire that is exposed however i tried to fix it the paperwork shows a triangle three prong connector and my bus has a circle 4 prong compatible 3 prong connector that is at the Transmission, Engine, Data link (in rear at operators panel) and at the driver seat Data link

How would you fix this issue properly

[cadillackid]

you sre right the yellow and green wires are the DataLink.. you kind of confused me with the run on of locations. are the wires pulled out near the engine? near the trans? ive usually seen a 3 pin connector with yellow / green / black.. if one wire is opulled out and the pin is missing you should be able to look down the connector and see the pin .. or a scuffed hole if the pin popped out with the wire

[Busboyz]

Yes the Yellow wire that is pulled out of its connector is right next/above the TCM all other Yellow Green and Black connectors seem to be in good working order.

Would this problem put the system into limp mode.

[cadillackid]

I’ve not seen a down 1939 link limp a trans unless it’s a 2008 or newer that has SEM enabled, doesn’t mean allison didn’t have others that limped one days I’ve just not seen them, that said you need to fix it anyway as even if you got all 5 gears back you’d ruin it from heat with the link down.

Your profile isn’t filled out so I have no idea what bus you have to begin to look for the wiring pin outs , again usually you can tell where something got pulled out from or see another connector half where you look for the wire on the other side.

The universal colors for j1939 are yellow green for can high and low and then black for reference ground. But leave it to navistar to use grey in places esp near the dash connector.

Somewhere I read kids were playing in the bus? Is it possible they trashed the shift linkage cable so it’s actually in “1” and not D? When you test drive it? That won’t fix the data but just curious..

[Busboyz]

Yes there were a lot of kids in and out of the bus that weekend and some of the littles were pulling on the shiftier, I thought the same that they may have trashed the cable so i checked at the transmission and watched the actuator arm move into every position as well as indication inside the driver seat.

I am convinced it something dumb i drove it there and it was fine then on the next start up bam!!! limp mode!!!

So a little history about it i bought it and did a complete in frame motor rebuild myself and have drove it almost 2k now on the motor everything has been a dream on it it worked and shifted great never had any codes or faults even on start up after siting for 2 years. I just dont get it now with looking at wires and connectors i found this yellow wire pulled out of its connector and the code is J1939 error

Im not sure how to properly fix this connection as i cant get the pin out of the plug i feel as if i am going to trash the whole connector if i keep messing with it not sure if you can buy the connector already together and cut to solder or what

[cadillackid]

you can buy a pin tool, i have various ones I use for extracting pins.. depending on the connector, new pins with pigtail can be bought and then pushed into the connector.. which connector is the wire pulled out of? the large many-pin connector on the trans TCM? the 3 or 4 pin connector in the harness? if I saw pictures of the broken connector I might be able to better guide you to what type of connector it is..

[Busboyz]

These are this sister plugs to the one that has the Yellow wire pulled out of the back of the group of wires that is at the Transmission. im pretty sure these are the data link cables but not totally sure. This group of wires are at the Engine ECM, Transmission TCM, and the Data link 9 pin connectors at the front and back of the bus

[cadillackid]

Yep those are indeed newer style data link connectors.. fix the yellow wire and likely issues will go away. That connector may be a dealer only item, hopefully there is a repair part, of not that is a data bus. You could splice into the good part of the yellow wire and then jump it to the yellow wire (immedatly) opposite of it and go.

You could also cut the bad connector off on both ends and replace it with a weather pal or metripak style connector that is weatherproof .. the main thing is that the wires are connected to each”s mate

[Busboyz]

I will try and contact a dealer on this part and see if its available from them. If not then i will look at trying to repair the wire and see if it fixes the issue i will keep you informed will try and look at splicing tomorrow just to get an idea of what it may entail

Cadillackid i cant begin to thank you for your input on this i will take some pictures and keep the page updated.

[cadillackid]

try this as a start..


https://www.peigenesis.com/en/shop/p...094.html#mates


thats the splice..



and the mate appears to be a 086-0068-000



I could see a 08 barely on your pic and the splice number. . so I think I got that right.. it looks like there is also a crimp tool in that site too.. now i have no idea how to order them.. however with an ITTCannon part number you may be able to go to work on it..


-Christopher

[cadillackid]

maybe this?


https://www.ebay.com/i/254629764295?...saAq7wEALw_wcB

[Busboyz]

With work and all the rain we have been getting here in Southeast Tennessee i have not had a chance to work on the ole girl. I have looked at the connectors and have had some long in depth talks with a few of my buddy mechanics who have basically told me what i already know that the right fix will be the connectors and the cheap fix will be the splice option. They also said splice it to see if that fixes it and if it does fix it properly from there. So i will be doing a splice on it hopefully soon if the rain holds out maybe tomorrow fingers crossed!!!

[sepudo]

Originally Posted by Busboyz

Hey everyone new to the site but have a total of 4 skoolies .
I have a 2003 IC bus with a DT466E and a 2000 series transmission.
i have this bus gutted and all open so i used it for a media room a couple weeks ago on a family camp out i took two buses there and the IC was where the kids were hanging out. So over the weekend there were 12 kids in and out of the bus (some mine and some not mine) anyhow some were playing in the driver seat and pulling on the gear shiftier, when i drove the bus there it was fine now the Check Trans light is on and it is stuck in low gear 18 mph might i add. Wondering if there is some easy fix or will i have to have a mobile company come and hook up to the bus for a diagnostic.

Thanks in advance

It's been years but I'm curious what was your solution to your check trans light issue...

It seems like I have the exact same symptoms and may have a can bus error issue related to either a yellow or green wiring along my harness.

Hoping to hear any insight you may have.

Please and thanks

[ewo1]

Originally Posted by sepudo

It's been years but I'm curious what was your solution to your check trans light issue...

It seems like I have the exact same symptoms and may have a can bus error issue related to either a yellow or green wiring along my harness.

Hoping to hear any insight you may have.

Please and thanks

A friend of mine has got a dt466/2000 setup and she had limp mode issues and the check trans light coming on.

Her problem was 2 fold. TCM was bad, sent it out for repair, limp mode gone but the check trans light still on.

The light problem was fixed by repairing the 120 ohm resistors on the TCM data lines.

From what I was told, the failing resistors also could throw the tranny into limp mode.
Again, from what I have been told...

[cadillackid]

the various allisons have multiple "limp" modes.. the true limp mode as allison defines it typically on an Allison 1000/2000 is only 3rd gear and reverse, no lockup..



with the physical shifter the transmission is capable of shifting into those gears via the valve body itself.. thats what the transmission will do if you simply unplugged the harness off the side of it or had a complete TCM failure..



there also are likely differences between 3rd gen (5 speed) and 4th/5th gen (6 speed) setups..



I had an allison Tech once tell me that the check trans light is Latched on at TCM powerup, then once the TCM boots it turns the light off for a second, then back on if needed for any sert code conditions.. I noticed this condition on my own 6 speed A41 TCM.. if I unplug the J1939 plug, the check trans light comes on, then goes off then back on again.. apparently the design was that if the check trans light never lit up you can suspect a power issue to the TCM, supposedly if it came on and stayed on then it meant the TCM never fully booted (again 3rd gewn may be different)..



my specific setup - the transmission will operate and shift gears if the J1939 link is gone (an MD3000 series may be different because it would mean the shift pad is probably not going to work).. my transmission will shift through gears 1-5 but will not operate Lockup.. it uses the torque converter slip rate to approximate torque being applied and deriving a throttle reading.. so that it tries to shift at a somewhat more optimum shift point and TAP (pressure)..



when the J1939 is down, the check trans light is on..


if something else goes wrong like a stuck shift solenoid (something common after a unit sits for a long time) then it will pick the safest gear it can be in as a limp gear with the solenoid operating in the position it believes it is in.. the allison uses the 2 or 3 speed sensors on it to determine what gear its in.. it will try and avoid a bind-up at all costs even if it means you get no gears.. or get 1st gear only.. I dont believe it will ever limp in any gear higher than 3.. at least from what ive read it wont.. for good reason.. you'd make a ton of heat very quick if you did a start-roll in 4th gear.. the 3-4 ratio change is pretty tall on all variants..



if the temp sensor reads an erratic hot fluid or out of range, I *believe* the transmision operates in the hot fluid mode which favors lower shift points and lockup on as much of the time as it can.. even if it lugs the engine a bit.. from the factory lockup can be set based oin the vocation and the manufacturer of the vehicle spec. for imstance on the origina chevy trucks they didnt lock up until 5th gear. most busses ive seen lockup fairly early into 3rd gear (similar to the way the MT643 did).. the hot oil program locks it early in second and elaves it on except perahps during the act of shifting..



if your J1939 wiring looks suspect then id def start there with getting it in order and checking your term resistors like EWO mentions.. but an all out limp may also be a stuck solenoid ot harness issue.. at that point it becomes almost necessary to have the ability to connect a scan tool (once J1939 is restored) and read for codes..