Can't start coach from key

[Roger Davis]

Eric,
I found it here and am reading through it now.
https://www.trucktransdiag.com/downloads/wtec3.pdf

Roger

[Roger Davis]

Eric,
On page 192 is the gray wire connector chart. I see battery power on pins 1 and 16 with ignition sense on pin 26 but for the life of me where does
it get ground from? The metal box is not used as a chassis ground by way of an external wire or mounting screws. Anyway I'm continuing to read
I'm just wondering if you agree with my pin assessment?
Roger

[Eric Maclean]

Roger
Allison calls it's grounds battery return
They are pin 17 and 32 in that diagram and should be gray wires .
You will find both the powers and grounds are provided through the VIM module.
He's the 1 and 16 are battery power and the 26 is the ignition power
They usually use two power feeds and two grounds too provide enough  current capability through the small ECM pins.
Page 67 in the troubleshooting manual will help identify the pin locations in the ECM and the pins for the power inputs to the VIM module.

Page 83 will show you the power path through the ECM over to the shift concel and the pin numbers to check at the concel as well as plug configuration.

Hope this helps
Eric

[Roger Davis]

Good morning Eric,
First off let me thank you once again for helping me grind out my homework.
Next, let me see if I follow your thinking. I'm going to test the Allison ECU (TCM) gray cable for power and ground and ignition sense with ignition on.
If no joy, go back to the VIM where voltage to the TCM originates.
But, if both fuses have voltage on them in the VIM, isn't that it's own verification that the VIM is supplying voltage forward? But I'm getting ahead
of myself prior to checking the TCM gray cable. Also I might add that the Power Pin to the shift pad is a different pin according to the drawings on
this TCM so it could still be the shift pad. I will check again the shift pad pin "R" for 12v.
Please comment on my "critical path".
Roger

[Eric Maclean]

Yep
Your right on you could start at the shift pad and work backwards if you like 
If you have power at the fuses in the VIM then it follows that you should have power to the gray ECM terminals ( unless you have a loose connection or bad wire in that harness.

Also if you have power and ground to the shift concel it should light up at the very least  with cats eyes to tell you it has no communication with ECM if power and ground are there and nothing lights up the problem is likely a bad shift concel.
Eric

[Roger Davis]

Eric,
Thanks for confirming the critical path. Question, on page 200 is the pin "signals" so I'm interpreting power on pin "R" and ground on pin "P".
Assuming this is correct, I am concluding that if there is power and ground on the cable to the shift pad, then the shift pad is bad and the worst
case scenario is a bad TCM if it is receiving proper voltage.
Correct or incorrect???
I might throw in that all my cabling appears pristine as in clean protected and corrosion free so I'll be very surprised indeed of wiring ends up
being the problem. I'm awaiting your confirmation on shift pad voltage before I dive in.
Roger

[Eric Maclean]

Yes
The separate sensor wire is a 5 volt reference wire that the shift concel uses for it's logic circuits to determine shift input status the same 5  volt reference  is also used for other sensors like the TPS ( throttle position sensor) and temp sensors ect.
The ECM uses the sensor  return voltage as it's sensor data for it's logic.

The shift concel communicates with the ECM via a serial stream data ( twisted pair) meaning the concel receives and sends data back and forth to the ECM the concel has its own processor built in to receive and send command status and receive gear selected data from the transmission through the ECM.

Sorry if this got a bit wordy
Hope it helps you
Eric

[Roger Davis]

Hi Eric,
It's the shift pad which I would have realized the first time I checked it but I was checking the wrong pins due to following the pins of the WTEC2.  No matter, thanks to you and the others I have learned so much more about my coach which is priceless so a big shout out and THANKS to all! It's the less expensive of the two electronic parts that it could have been so I'll be grateful for that. I've seen that parts like this can be purchased as refurbished for considerably less with a warranty and all so the online shopping begins.
Might you have a suggestion for this? At least the hunt for the culprit is finally over. WHEW! I think I'll take the boat out in the ocean and get my head straight! I have another project involving pulling a cat 5 cable for the new Xantrex inverter from the bottom bay to just above the passenger's head as the existing wire isn't compatible. But that's for another day but soon.
When the new part gets in I'll let you know it's working.

Roger

[Fred Brooks]

    Roger,
Glad you got a handle on it. Eric is a great chassis technician and knows his stuff! The Cat 5 short cut is thru the refer cabinet. Cheers, Fred

[Eric Maclean]

Roger
The last PM I sent you is actually a link to a company that rebuilds the shift pads and will test it for you  just to be sure
A company called     TRANSMISSION INSTURMENTS

https://www.transmissioninstruments.com/


https://www.transmissioninstruments.com/wteciii/

Hope this helps
Eric

[Bill Lampkin]

Roger, do you know Xantrex makes an adapter so you can use old cable with new inverter? I did this and all works fine.

Freedom SW telephone to network cable adapter   808-9010

[Roger Davis]

Hello again everyone,
It's been a few weeks since my last post on this topic so I wanted to share the conclusion. First I want to give a huge shout out to everyone for helping out with an extra big shout out to Eric McClean as without Eric's interaction, I might very well be struggling or possibly have given up and thrown money at it. It turns out it was the ECU and not the shift pad. It is imperative that you use a 9v battery and check the shift pad not just the 12v and ground which in my case were present. There is a 5v pin which if it is not included in the shift pad test, it will not light up. Transmissioninstruments.com is a small family business out of Texas that specializes in rebuilding Allison transmission ECU's, shift pads, and a few other electronic components. I might also
add that I was informed by them that the 2001 and surrounding year parts are notorious for power supply board failures. I asked John if his fix addressed this issue and he said none have come back as of yet. Just in case anyone's interested, there's a 2 year warranty on his work. That's pretty amazing for electronic work!!!
Just in case I included the shift pad in the box so they could test it (no charge for this). I was also informed that the shift pad almost never fails if anyone's interested. So, for $595.00 and my cost of shipping to them (they pay shipping back), my coach starts from the key again and of course shifts as it should.
Again, thanks to all of you for your assistance!
Roger Davis