Allison transmission - unable to communicate with diagnostic laptop

April 23, 2015, 01:26:17 pm

All,

Suggestions please

Allison 3000MH transmission - no issues Whilst in the workshop for something unrelated today, the local Allison tech came in (to work on somebody else) - never one to miss an opportunity to learn !! - I asked him if he would plug in to the motorhome when he finished and discuss his findings

No problem he said - but that is where his problems started !!

Located an oblong and a circular connector up behind the dash - the tech recognised the oblong connector as belonging to the WTEC III that he was after to communicate with the ECU, however the oblong connector would not 'talk' to the ECU We confirmed the continuity of the wires from the ECU to the diagnostic point - all intact We tried the circular connector (to which wires 793 and 794 lead) - again no communication We tried a similar circular plug in the battery compartment at the rear of the coach - no communication

An enquiry of the Allison main agents on this side of the pond suggested a CANBUS failing, but that checked out fine

Joined by another Allison tech

We tried an alternate ECU to the oblong plug - still no communication We tried a different laptop to the oblong plug - still no communication

(Everything at the minute points to the ECU not sending data up the wires to the diagnostic point - but that could prove expensive !!)

We are running out of ideas!! - and there are too few of us (RVs) on this side of the pond for anyone to be really up to speed

Appreciate any suggestions / pointers from anyone who might have been looking over a tech's shoulder when your transmission was diagnosed / connected

(Have not yet followed up with KW or the factory - if you think it worthwhile)

Thanks in anticipation

Ian S.

Allure 430 Hood River 2005 - #31321 Cat C9

Allison MH3000

Re: Allison transmission - unable to communicate with diagnostic lap

Reply #1 – April 25, 2015, 01:38:13 am

Yahoo Message Number: 100364

Forgot to sign. Mike Gunn. 2006 inspire

Re: Allison transmission - unable to communicate with diagnostic lap

Reply #2 – April 25, 2015, 01:38:39 am

Yahoo Message Number: 100366

Check the J1939 wires at the rear of the coach. Country coaches have a problem with the wires getting hot and melting together they might look fine on the outside but are shorted internally. They are mounted too close the the exhaust system. The wires are only 70 deg centigrade wires. Mine melted together and it took three Allison shops and then the CC factory to get it fixed. if I remember right the ohms is 135 between the rear resistor and the front resistor. If you need to have them cut the wiring outside the engine compartment and test the wiring.

Re: Allison transmission - unable to communicate with diagnostic lap

Reply #3 – April 25, 2015, 03:45:55 am

Yahoo Message Number: 100369

Many thanks Mike - somewhere else to us to look when we return to the coach

This is the sort of previous experiences I was seeking - a great help

Hopefully others may be along in due course

Ian S.

2005 Allure 430 Hood River # 31321

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