Can't start coach from key

[Eric Maclean]

Roger
On page 106 in the troubleshooting manual gives the pin out for low voltage codes which would apply to you condition.
Dtc po880 on page 290 should be a better discription of your problem and the pin out at the ECM to check for power a d grounds to the ECM without the ECM powered up both ig itio power and battery direct power the shift concel won't power up .

Eric

[Roger Davis]

Eric,
I looked at page 126 but from what I get from that, the engine needs to be running first which is the problem. Your first order of business was to
remove the harness from the TCM and check for voltage and ground and of course corrosion. I'm going to start that now and will report my findings.
As far as reading codes from the plug, and without a digital reader capability, I have no idea how you want me to proceed. While I am fiddling with
connections, I will also check the shift pad for 12v and ground (which I don't expect to find unless the pad is fried). Also I wanted to ask you if there is
a possibility of one of the six relays in the VIM could be bad. In waiting for your response today I tried a search for a replacement for one of those
Bosch relays and thought to switch out one at a time in hopes that might be it but seems to be a discontinued part #.
Do you think a bad relay is possible?
Anyway, I'm heading out to the coach to perform the voltage tests and will report my findings.
Thank you for sticking with me. Hopefully we'll figure it out.
Roger

[Keith Moffett]

Just an aside.  Perhaps too obvious but have you checked to see that the remote start button at the rear is switched back to front start?

[Eric Maclean]

Roger
Sorry I only meant for you to use the pin numbers with ECM unplugged to determine if you have it ition power battery power and grounds where they should be .
My bet is you don't have one of the power feeds.
Keith brings up a good point if the rear run switch is not turned to front start you will have no forward controls.

If the rear run switch is in the front start position and the shift concel is dead try switching the back to rear start and checking the consell.
I believe even from the rear start position the transmission has to verify neutral to allow starter operation

Eric

[Eric Maclean]

Roger
I know this wiring diagram isn't the same year model as yours but it should be close .
In coach assist 1996 patriot wiring diagrams page 18 will show you the wiring for the rear start and ignition power flow to the transmission control module it shows the power feed through a relay in the Transmission VIM module.
Before condemning the relay in the VIM check at the rear engine switch they are a common failure due to the environment they live in .

Eric

[Roger Davis]

Wow you guys have been busy while I have been busy!
Okay first to address rear start station, there is no front/back switch on my coach. Never seen it never switched it.
Next, there is no power to the shift pad with or without ignition on.
The metal box in the picture I sent appears to be of the ECU. Picture attached. It has 3 32pin cables going to it. Blue, black and grey.
If there is anything to check on this module please advise. I haven't yet located the pin chart but I will. With that being said I still have to
locate the TCM. Anybody know where that might be hiding??  Anyway, when I do find it please confirm--I understand I need to check pins 2 and 70.
I'm guessing pin 2 is the ignition.
Am I thinking this correctly??
Roger

[Roger Davis]

Eric,
I'm looking at the 1996 wiring diagram page 18 as suggested. CB21 & CB22 would certainly be suspect however they've been tested and are fine.
At the top right hand corner there are 2 20amp fuses directly in a vertical line from each other. Might you know where they are actually located?
Roger

[Eric Maclean]

Roger
Sorry for the delay the two inline fuses are those found in the battery compartment.

Do you have transmission power to the shifter when in the rear start mode at the service panel ?
Sorry just read your post that states you have no rear run switch.
Do you have a picture of your service bay ?

[Roger Davis]

Good morning Eric,
Thanks for hanging in there with me. Here is the pic I already have in my phone and I assume you are referring to this bay vs. the electrical bay up
front driver side. I still need to know where I might locate the TCM with that 80 pin connector and if you would please confirm which pins to check.
I'm guessing pin 2 and 70 with pin 2 being ignition.
For a mere $12 I am buying a VIM relay and will change them out one at a time just to either rule out or hopefully solve the issue.
As far as your question as to when I start remotely and with the engine running, the shift pad is still dark. Just to add...the picture does not include
the relay tray w/fuses however I have checked all of them and all good. Is any of them the 20 amp ones in the '96 wiring diagram??
Roger
ps if you request more or better pictures of service bay, just ask

[Roger Davis]

Eric,
I took the following pictures so you might see everything. Please let me know if you'd like to see anything else.

[Eric Maclean]

Roger
Have you checked in the compartment under the shift lad to the ?eft of the driver's seat for the TCM
when. Checking for TCM power and grounds

For battery direct power should be 12 +volt  at pins #70 and #10

For ignition power should be 12+ volts with ignition turned on at pin #63

The TCM should be grounded at pins #69 and 6

The low voltage tests mentioned earlier will help you with these pin numbers and location in the 80 pin plug
Just ignore the criteria for setting the code the fault is the same with the exception that the fault did not take place with engine running.

[Roger Davis]

Eric,
I just got done swapping all 6 relays in the VIM and unfortunately, no joy. The only thing in the cavity under the shift pad left of the driver
was the metal 3 harness ecu for the Allison. I am yet to find the TCM with the 80 pin plug so I can test for 12 volt. I was really hoping
you were going to direct me to it. Is it possible that it's attached to the frame rail somewhere in the back of the coach and only accessible from underneath?
Roger

[Eric Maclean]

Roger
I'm sorry I just went back and checked your pictures the metal box you have found is the Allison TCM how ever your coach has a newer Allison configuration the old 80 pin unit was referred to as ( W tech 2 ) the system you have is called A tech 3 it was the next generation of Allison controls and the trouble shooting manual is different .
We don't have that one in the library yet so we'll have to do some research.

Did you have voltage at both fuses in the VIM module with the key on ?

[Roger Davis]

Eric,
I'm glad I don't have to crawl around like I was fearing. Something worth mentioning, My coach is a 2001 and that seems to be the year missing
from coach assist wiring drawings. I can see similarities as I've been toggling between different years.
Does anyone know if there is a fuse inside that silver box? Anyway, if I understand you correctly, you're attempting to find drawings for that TCM of mine.
Once again, thanks in advance,
Roger

[Roger Davis]

Eric,
Sorry forgot to add, yes to voltage across both VIM fuses. One of them always 12volts the other only when key is on.
Roger