Diagnosing Allison 2500 Transmission Issues on 2007 Thomas C2 Freightliner

[nikitis]

1000 AND 2000 PRODUCT FAMILIES TROUBLESHOOTING MANUAL—ALLISON 4th GENERATION CONTROLS​

Limp Home Test
With the ignition in the OFF position (engine not running), the selector in N (Neutral), and the parking
brake set, remove the 80-way connector at the TCM.

It will be necessary to provide battery power at pin 41 of the 80-way connector in order to energize the
neutral start relay. This can be accomplished by using a jumper wire between pin 10 and 41 at the 80-way
connector.

When the engine is restarted, the transmission will default to a “limp home” capability. In this state,
PCS1 (de-energized) allows C3 clutch to be applied. If the selector valve is moved to the reverse range
position, main pressure will be routed to C5 clutch, allowing reverse operation. If the selector valve is
moved to the drive range position, main pressure will be routed to C1 clutch, allowing third range
operation.

This allows a technician to use “limp home” capability to determine if a hydraulic or an
electrical problem exists. If reverse and third ranges are available in “limp home,” an electrical failure
may be indicated. If only one of the two ranges or neither was obtainable, this may indicate an internal
hydraulic failure (failed clutch, stuck valve, or solenoid failure). The clutches that could possibly have an
indicated failure in “limp home” are C1, C3, and C5.

Great info. Learned something new today.

 

[ewo1]

Great info. Learned something new today.

Here's the first half of the troubleshooting manual page...

BASIC KNOWLEDGE

1000 AND 2000 PRODUCT FAMILIES TROUBLESHOOTING MANUAL—ALLISON 4th GENERATION CONTROLS​

TCM/Vehicle Harness Setup
On the vehicle, use the J 47276 “T” Breakout and TCM Reflashing Harness to connect the Allison
DOC™ For PC–Service Tool directly to the TCM to bypass the Diagnostic Tool Connector.

Use the Dearborn DPA4 USB Translator Device Kit (P/N: J 47943) to establish connection between the
PC and the TCM.

Example: When communications are not available at the Diagnostic Tool Connector on the vehicle,
DTCs can be read directly from the TCM using the Diagnostic Tool Connectors on the J 47276
“T” Breakout and TCM Reflashing Harness.

Use one of the following Diagnostic Tool Connectors on the harness to establish a diagnostic connection between the TCM and the Service Tool (refer to Figure 3–3):
• J1939-13 connector (for J1939 communication)
• J1962 connector (for GMLAN “high-speed CAN” communications)

NOTE: To use the J1962 connector, an additional cable (J 47949) is required. J 47949 is available for
purchase from SPX/Kent-Moore.

5. When a problem exists but a DTC is not indicated, refer to the General Troubleshooting Section
(Section 7) for a listing of various electrical and hydraulic problems, their causes, and remedies.

6. If a DTC is found in the TCM memory, save all available DTC and failure record information before
clearing the active indicator (refer to Section 5).

7. When certain DTCs are active, a range selection into reverse or forward may not be possible. To determine if a failure is electrical or hydraulic, perform the following “limp home” test.

 

[osg828]

Great info. Learned something new today.

so far 10 amp fuse in fuse block under hood,(engine bay)is good,but on the wiring diagram you sent me there shows on inline from battery to tcm,I have to find that one,and there calling for a big storm this weekend,so probably won't get to that for awhile.One thing I haven't mentioned yet is that I have took out all the emg. door switches,but don't think that would keep it from moving?Also moved batteries to inside bus much easer to work on and disconnect.

 

[ewo1]

One thing I haven't mentioned yet is that I have took out all the emg. door switches,but don't think that would keep it from moving?

Not necessarily the case...
Depending on how the bus was ordered, the tranny TCM has I/O options that can and will either apply the parking brakes or not allow the transmission to go into gear.

Again, depending how it was ordered. This is part of the CIN information (programming) of your TCM.

I swapped TCM on my '99 bus which has a 5 speed MD3060 with a 6 speed TCM from a 2005 bus also with an Md30360 and because the donor bus had a wheelchair lift my bus would not go into gear.

I had 2 ways of fixing that, reprogram the TCM so that the i/o feature is disabled or do a hard wire jumper to signal the TCM that the wheelchair sensor is closed, which is what I did to get it fixed.

On a Thomas I do not really know if emergency door switches are tied into the TCM.
You should really try out the limp home test.

 

[osg828]

Not necessarily the case...
Depending on how the bus was ordered, the tranny TCM has I/O options that can and will either apply the parking brakes or not allow the transmission to go into gear.

Again, depending how it was ordered. This is part of the CIN information (programming) of your TCM.

I swapped TCM on my '99 bus which has a 5 speed MD3060 with a 6 speed TCM from a 2005 bus also with an Md30360 and because the donor bus had a wheelchair lift my bus would not go into gear.

I had 2 ways of fixing that, reprogram the TCM so that the i/o feature is disabled or do a hard wire jumper to signal the TCM that the wheelchair sensor is closed, which is what I did to get it fixed.

On a Thomas I do not really know if emergency door switches are tied into the TCM.
You should really try out the limp home test.

Probably what I will do,I pulled all the wire back to where it comes in along side of driver,only 2 wires.We are expecting large snow storm this weekend so might be a while.Thanks for the info...

 

[ewo1]

Probably what I will do,I pulled all the wire back to where it comes in along side of driver,only 2 wires.We are expecting large snow storm this weekend so might be a while.Thanks for the info...

Yeah, working with fingers freezing...NO THANKS!

Remember, while shoveling the snow, drink lot's of Blackberry Brandy and you will stay warm!

 

[osg828]

Probably what I will do,I pulled all the wire back to where it comes in along side of driver,only 2 wires.We are expecting large snow storm this weekend so might be a while.Thanks for the info...

Still kinda of baffled on this,cause in warmer weather I jacked up the back removed the wheels,started it went through the gears,and took speedo up to about 40 mph,yeah Brandy sounds good but in my old age just gives me headaches.......

 

[osg828]

1000 AND 2000 PRODUCT FAMILIES TROUBLESHOOTING MANUAL—ALLISON 4th GENERATION CONTROLS​

Limp Home Test
With the ignition in the OFF position (engine not running), the selector in N (Neutral), and the parking
brake set, remove the 80-way connector at the TCM.

It will be necessary to provide battery power at pin 41 of the 80-way connector in order to energize the
neutral start relay. This can be accomplished by using a jumper wire between pin 10 and 41 at the 80-way
connector.

When the engine is restarted, the transmission will default to a “limp home” capability. In this state,
PCS1 (de-energized) allows C3 clutch to be applied. If the selector valve is moved to the reverse range
position, main pressure will be routed to C5 clutch, allowing reverse operation. If the selector valve is
moved to the drive range position, main pressure will be routed to C1 clutch, allowing third range
operation.

This allows a technician to use “limp home” capability to determine if a hydraulic or an
electrical problem exists. If reverse and third ranges are available in “limp home,” an electrical failure
may be indicated. If only one of the two ranges or neither was obtainable, this may indicate an internal
hydraulic failure (failed clutch, stuck valve, or solenoid failure). The clutches that could possibly have an
indicated failure in “limp home” are C1, C3, and C5.

Thanks for the info,i'll try that when weather breaks.Is the plug left off the TCM while this in done?

 

[ewo1]

Thanks for the info,i'll try that when weather breaks.Is the plug left off the TCM while this in done?

yes, in effect you are removing the TCM and testing basic/default transmission function in order to determine if your issue is electronic or hydraulic. Once that is determined you will have a btter idea on what is going on with the tranny.

 

[osg828]

yes, in effect you are removing the TCM and testing basic/default transmission function in order to determine if your issue is electronic or hydraulic. Once that is determined you will have a btter idea on what is going on with the tranny.

ok,thanks,I will try after this snow storm they are predicting...South Jersey.....