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Gunnyjeep

No power to Allison Transmission Control Panel

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I'm hoping that someone can point me in the right direction, we've been dealing with a starting issue since Jan 2nd, while I'm not a RV Mechanic I am a retired after 40 years as a Aircraft Mechanic so I do have some troubleshooting experience.  Here's my issue - I sent this to a highly rated RV mechanic in Las Vegas NV (we're at RV Resort in Pahrump NV).

"I'm hoping you can help us, we're a little out of your area in Pahrump but we're in need of service.  2004 Holiday Rambler Imperial DP 400 HP Cummin's the issue is that we're not getting power to the Allison Transmission Control Panel. I have checked fuses with no luck, issue started with ATC light flickering about 1/2 hour before we stopped, but no issue with running until we went to leave 3 days ago, turned on the ignition and first thing I noticed was the wait to start light wasn't lit, waited a few minutes then tried again with no luck, went ahead and tried starting but it was a no go, checked fuses all good, shore and chassis batteries are fully charged (did have one of eight shore batteries with a broken ground post so I replaced with same AGM amperage battery, turned off all pwr to reset computer but a no go,  next was to check for codes at the engine diagnostic port - no power at the port, I have a wiring diagram but it doesn't show the diagnostic port that I've been able to see so I can't trace where the common fuse would be.  I know it's common because if I hook a hot wire to the power pin on the port the trans control panel lights up and starter solenoid clicks but it doesn't get enough juice to start."

This was the reply I received this morning from the mechanic:  

"I am sorry but we have run into this issue before and were not able to resolve, and do not want to risk the trip and labor involved trying to figure it out and not be able to. 
We wish you luck with this issue."
 
I've already had 1 mechanic spend a couple of hours on the coach and he got no further then I, another mechanic I had a appointment with called back and said he'd be a few hours because he forgot his wife had a doctors appointment - that was last Friday.   My last resort is calling FMCA road service and get this coach towed 60 miles to Las Vegas.  Thanks

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The way i would start troubleshooting is to follow that power wire back from the port through the harness. That is really the only way you’ll find the problem

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1 hour ago, sstgermain said:

The way i would start troubleshooting is to follow that power wire back from the port through the harness. That is really the only way you’ll find the problem

Found this White Wire on the right side of the transmission that wasn't connected, the only place it looks to connect to is a sensor, it's not a "hot" wire and the grime on the end tells me it's been hanging loose for awhile, but I'll keep looking.

 

IMG_1444.JPG

IMG_1445.JPG

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Have you confirmed the ground connections to the harness are good? Seems like quite a few problems like this end up being a bad ground, so that's always my first step.

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Gunnyjeep, Welcome to the FMCA Forums!

Do you have this electrical compartment on the right rear?

there is a relay labeled engine ignition, I believe that powers the ECM and TCM. I would check it for power and grounds, the schematic for the relay is stamped on the side.

323AADB7-FC1B-40B2-97AA-225CF2523886.jpeg

0D73F4CD-59AA-47CF-9061-B5A937CC3210.jpeg

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You say you checked the fuses, which ones, where,   Did you check fuses in the module box under the shift plate. There are 2 in it, 10 screw to access it. How did you check the fuses, by looking at them or with an ohm meter? Just ask me how I know this issue... I spent 100 bucks and less than 10 minutes of a techs time to solve the same issue. I caused the issue changing/cleaning in the battery compartment. Be sure too that there are 2 hot wires connected that service this part of the system.  

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37 minutes ago, RSBILLEDWARDS said:

You say you checked the fuses, which ones, where,   Did you check fuses in the module box under the shift plate. There are 2 in it, 10 screw to access it. How did you check the fuses, by looking at them or with an ohm meter? Just ask me how I know this issue... I spent 100 bucks and less than 10 minutes of a techs time to solve the same issue. I caused the issue changing/cleaning in the battery compartment. Be sure too that there are 2 hot wires connected that service this part of the system.  

I actually pulled and replaced fuses in the electrical compartment (I learned this lesson also the hard way), haven't checked the module box (wasn't aware of it - have the side panel off and can see the bottom of the shift plate, I see a box mounted below it with two plugs going to it. can't see much else due to the wiring harnesses.

 

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11 hours ago, RSBILLEDWARDS said:

Did you check fuses in the module box under the shift plate.

Bill, he also doesn't have power to the Cummins ECM (no wait to start lamp).

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I had to remove the pad from inside coach, then the screws for the box.  The "flickering of the ATC for 1/2 houre", suggests a loss connection or bad ground.  not fuse. 

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Check all connections for continuity. Many problems from not having a good connection. I kind of remember a earlier post about bad connections being a problem.

Bill

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Here's where I'm at, On the VMI I have 13.4 volts at Pin J1 and J2 and 2.2V at pin C1 with the ignition off, when ignition is on pin J1 and J2 drops to 5.4V and C1 stays at 2.2V From the VMI to the ECU I'm not getting any power with or without the key, batteries are charged and no difference with battery boost pushed

Allison wiring diagram.JPG

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Have you looked at ignition switch?  13.4 to 5.4 is a big draw!  If the switch is good, move on to solenoid.

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18 hours ago, Gunnyjeep said:

Plugged everything back in and tested the 2 fuses in the VMI which both read 12.3V

vmi.jpg

 

18 hours ago, Gunnyjeep said:

Plugged everything back in and tested the 2 fuses in the VMI which both read 12.3V

vmi.jpg

What voltage do you get at the Diagnostic Connector terminals A and H.

Jim

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Gunnyjeep. Welcome to the forum. Thanks for your service!

Could you post the Make, Model and year of the coach also include the model of the transmission.

If everything  was wired the same it would be to simple . Like flight line avionics nothing stands still . LOL

There are some highly skilled members on this Forum. Maybe if you offer the information requested we can get everybody on the same page

Rich.

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24 minutes ago, DickandLois said:

Gunnyjeep. Welcome to the forum. Thanks for your service!

Could you post the Make, Model and year of the coach also include the model of the transmission.

If everything  was wired the same it would be to simple . Like flight line avionics nothing stands still . LOL

There are some highly skilled members on this Forum. Maybe if you offer the information requested we can get everybody on the same page

Rich.

2004 Holiday Rambler Imperial DP 400 HP Cummin's

Rich, should be a 3000 series Allison

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With that information It is possible there is a 10 amp fuse located in the VIM(Vehicle interface  module) Most of the wiring in this module is for relay circuits used to get the different control modules cross connected properly .Could be the point where the supply voltage is interrupted. Not much information on this fuse location out on the network.

Hope this clears the missing Allison power.

Rich.

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1 hour ago, DickandLois said:

With that information It is possible there is a 10 amp fuse located in the VIM(Vehicle interface  module) Most of the wiring in this module is for relay circuits used to get the different control modules cross connected properly .Could be the point where the supply voltage is interrupted. Not much information on this fuse location out on the network.

Hope this clears the missing Allison power.

Rich.

It also appears he is missing ECM power, "no wait to start light" with the ignition switched to ON.

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UPDATE: Problem was a power wire to the starter that was pinched, without a load it was reading 13.4 volts as soon as you tried to start it dropped to 5.2 volts. We are back to being mobile - Thanks Everyone for the help!!!

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27 minutes ago, Gunnyjeep said:

UPDATE: Problem was a power wire to the starter that was pinched, without a load it was reading 13.4 volts as soon as you tried to start it dropped to 5.2 volts. We are back to being mobile - Thanks Everyone for the help!!!

Where was it Pinched at? 

Glad you got it resolved!

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41 minutes ago, Gunnyjeep said:

UPDATE: Problem was a power wire to the starter that was pinched, without a load it was reading 13.4 volts as soon as you tried to start it dropped to 5.2 volts. We are back to being mobile - Thanks Everyone for the help!!!

As mentioned above Good job>Hope we did not muddy the water to much! Good to know you are back on the road..

Rich.

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