Sunday, January 28, 2007

Allison 3000 Series New World Automatic Transmission-troubleshooting a fault code

We recently had a no shift problem on one of our 2002 Thomas HDX pusher buses.

The code read on the pro-link was 45-12 which is an open circuit to the A solenoid. The A solenoid controls shifting into neutral which explains the no shift problem.

Since solenoids A, D, and J feed off the same voltage source we are probably looking at a low side or ground side wiring problem.


Disconnect the Deutsch bulkhead connector at the transmission and the T-connector or Blue connector at the ECU located under the removable cover on the right side of the dash.

Locate A and G circuits[trans. side] which is marked on the connector face. Run a jumper[Kent Moore #J39197] and check the corresponding wires at the ECU end, they will be T-1 and T-4. Using a digital multimeter [do not use analog meter!] check for opens, shorts and excessive resistance.

Check continuity and resistance to the A solenoid in the transmission itself. The control module[bottom side of trans.]houses the solenoids and hydraulic controls.

The result is resistance in the ECU to Bulkhead connector. So we will run a new shielded twisted pair of wires for the A solenoid circuit.



Replace wire ends for terminals T-1 and T-4 using Kent Moore J34182 Crimping tool. Once lock is remove from T-Connector The wires easily slide out of plastic locking tooth.







Lock newly installed wires into T-Connector at ECU and install
back into ECU with red plastic lock.








The Deutsch Bulkhead Connector unlocks and locks easily from transmission end when making repairs.









Use [Kent Moore J-38582] to remove wire ends from bulkhead connector.








Crimp new ends on replacement wiring using [Kent Moore J-38125-7] crimping tool.








Push in new wire end into bulkhead connector using [Kent Moore J-41194] insertion tool.

The code went away after this repair and the bus went back into operation. We have had a lot of success with wire replacement to fix transmission code problems since the wiring is exposed to the elements and tend to get damaged from the plastic convoluted loom that is used on most School Bus applications.

If the wiring would have checked out OK them we would have had to drop the Transmission Control Module and most probably would have had to replace the A Solenoid.

The tooling noted in this repair is required to do a proper job. Of course the cost of repair is diminished greatly when you can perform your own troubleshooting and repair. The WTEC 2 or WTEC 3 troubleshooting manual is essential with this kind of work.
The WTEC 2 ECU has two connectors while the WTEC 3 ECU has three connectors for easy identification of both systems.

WTEC=World Transmission Electronic Controls.

6 comments :

Anonymous said...

Great example of solving a wire problem and or diagnosing possible problems with solenoids in the transmission itself.

I'm looking for a copy of the WTEC 3 trouble shooting guide, and specifically what the code 14-627 means.

Is Allison the best (only) choice a the source for this publication ?

John Whelan said...

We get all our literature from Allison [best choice] and don't know of any other sources.

Codes are a 4 digit number like
35-00 for example. If you want to double check and send me the code I will check for you.

jewhelan@telus.net

Bill Moyer said...

Dear John,

I can't tell you how happy I am to find your blog. I lead a non-profit group getting ready for a cross country tour of our parade the Procession For The Future.

The problem is that the bus that was donated to us doesn'e go into 3rd gear, and I'm not sure if it's a simple problem to fix - or a disaster requiring a new vehicle.

The possibly related issue is a transmission related breaker that continually pops, making the transmission disengage completely.

The bus is a surpluses inter-city transit vehicle. I'm no mechanic so I'm just repeating what the person donating it said, i.e. it's an Orion Allison, 3 Speed Automatic. Max speed 62 MPH. U
The engine is Detroit Diesel 6 V (1992). Bus is maybe a 1980 era.

Does this breaker issue and not shifting from 2nd to 3rd sound familiar? Any ideas of what to do first?

Thank you again,

Bill Moyer
Director
Backbone Campaign
206-408-8058

The Helper said...

If you need transmission wiring harness connectors such as Bulk head, Terminals, ECU connetors, GEN4 transmission wiring connections
visit
www.transkittech.com

Anonymous said...

Hi John,
My name is Allison and my husband and I have a repair business. He is very knowledgeable about most things but we have been working on a 3116 of and on for about a month and he can't figure out what the problem is. We have changed the fuel filters and checked the lines for air. We have change the injectors and have retimed them. The govenor is knew along with the pump. The problem is that it keeps putting out black smoke when you start it and it will only run for a few seconds. He says it sounds like it is getting to much fuel but he doesn't know what else to do. If you could help with this I would be really greatful. Thank you!!!!!

J. E. Whelan said...

Hello Allison,
The one step when replacing injectors that must be done is seating the injectors using the CAT seating tool. The injector seating cups in the head must be in good shape as well. they are machinable or replaceable if needed. If not seated properly there will be compression leaking into the injector bore causing pressure build up within the fuel supply throughout the head fuel gallery and a very poor running condition. One way to check this is to see if there are bubbles in the return fuel back to the tank.