Transmission not 'talking' to diagnostic laptop

[IanSmith-UK]

All,

Hello from the UK - where unfortunately RVs are not plentiful, so we struggle for guidance / advice / suggestions when we hit a snag

Country Coach 2005 - Allure 430
Allison 3000MH transmission - no issues - drives fine

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!!

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

Thanks in anticipation

Ian S.

[Skip426]

From way across the pond , and then some.
Ian. I'd be very tempted to put things back together , road test for good operation then follow the procedure in this PDF to check for codes. If no codes, let well enough alone.

[DAJO]

I don't have the fancy stuff the dealers have, but when I connected Silverleaf vmspc to my last 2 motorhomes they both used round plug. The Scan gauge Diesel also uses the round port, both were under the front dash. Both of these can read codes.

[BluegrassFan]

How many pins are in the round connector? If 6 pins then the connector is for the J1708 bus. If 9 pins then the connector is for the J1939 bus. The connection between the Allison ECU and the J1939 bus on my 2002 Allure had the + and - wires swapped from the factory so the Allison transmission was unable to communicate on the J1939 bus.

[IanSmith-UK]

Originally Posted by BluegrassFan

How many pins are in the round connector? If 6 pins then the connector is for the J1708 bus. If 9 pins then the connector is for the J1939 bus. The connection between the Allison ECU and the J1939 bus on my 2002 Allure had the + and - wires swapped from the factory so the Allison transmission was unable to communicate on the J1939 bus.

The Deutsch round connector (up behind the dash with the Allison diagnostic port) has 6 pins although only 4 are in use (A,B,C,E) - appears that the 4 wires from the black plug on the Allison ECU are duplicated - there are also the 2 wires (E793 and E794) which piggyback onto the white and blue wires that come up from the black plug of the ECU

?? Serial communication interface - I am guessing this is a separate 'module' - any ideas where it might be 'hiding' ??

Thanks in anticipation

Ian S.
Country Coach 2005 Allure 430 Hood River #31321