LMTV CTIS Question

cjacksoncpa

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Ok, since this thread is about 5 lights flashing on the CTIS. I started to follow the TMs and got didn't get continuity on the socket A of the P84 connector and it says "
Repair wire 3032 from connector P84 socket A
to terminal lug TL85 (para 2-40) or replace
start and charging cable assembly (para 7-82)."
First how do I find "para 2-40" ?
Please excuse my lack of knowledge but is there any way to open up the plug to see if it is disconnected? I started tracing the wire and got part the way up and haven't found any problems with the wire. Any advise would be greatly appreciated.
 

Suprman

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Some plugs can be easily opened and others cannot. Get a tone tracer. Connect to the pin you think is bad and tone trace all the wires in the bundle. That pin may be connected somewhere else. In my experience, wiring damage is usually visible physical damage. If you inspected and everything looks good the harness is usually ok. Sometimes the Tm wire tracing can be confusing and every once in a while the older TMs have a wrong wire number here and there. Or updates have been done changing little things here and there and your older tm does not have it.
 

cjacksoncpa

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Wet Tank noise

I am uploading a video of a noise that is coming from the wet tank when the truck is off but there is still pressure in the tank. When I opened the drain valve it stop for about five to ten seconds and then restarted. Does anyone have an idea of if this is normal?
 

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tennmogger

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That's a small leak around the edge of the diaphragm in the over pressure valve. Mine was doing that, but faster. You can probably isolate the noise with a listening tube or feel the air escape.

You can pull the top off the o p valve (the thing that looks like a pressure regulator) by removing those two Phillips head screws. Drain the wet tank first, of course. It's also under spring pressure. Count the threads showing on the adjuster, back it out to relieve spring pressure and the job gets easier.

I cleaned and rebuilt mine once but it still leaked because the cap is warped from the years of being under spring pressure. Someone on here suggested a touch of RTV on the edges of the diaphragm and that worked great.
 

cjacksoncpa

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Thanks Suprman and Tennmogger for your advice and counsel!! The list of things to do the next time I work on the truck keeps growing. ;-)
 

Suprman

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Whats the best way to interface with the lmtv ctis control? Its my understanding that on the A1 C7 trucks that have data bus you can use a laptop with the dana software and access it thru the engine diagnostic port. Not sure about 3126 A1 trucks though. Supposedly there is an elusive Y cable in some of the later diagnostic kits.
Will
 

Suprman

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Not always on lmtv. Just indicates a hardware fault. The air tank pressure switch not closing will cause a time out error and give 5 solid leds. I believe pneumatic valve not responding can do the same.
 

Stellaevil

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Michigan
I just browse the new trouble shooting manual and could not find anything about 5 solid lights.
Thanks for taking the time to look at the manual. You are correct the 5 solid lights is not mentioned. We could not account for strange ECU behavior due to internal circuit failure, because basically anything goes. 5 solid lights is not a normal function condition so the conclusion that the ECU is "Toast" is most likely correct.
 

Stellaevil

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Location
Michigan
Whats the best way to interface with the lmtv ctis control? Its my understanding that on the A1 C7 trucks that have data bus you can use a laptop with the dana software and access it thru the engine diagnostic port. Not sure about 3126 A1 trucks though. Supposedly there is an elusive Y cable in some of the later diagnostic kits.
Will
A1 vehicles have a CTIS ECU that can communicate through J1708. Depending on when the truck was built the 2 com wires may or may not be connected to the vehicle diagnostic service bus. Black 9 way Deutsch. Find the connections in the CTIS service manual and ohm them out. if they are not connected you need a"y" cable to that basically breaks them out. Then using a laptop, the Dana DDT software, and a Com box you can talk to the CTIS. read fault codes, take control of specific functions, and use the troubleshooting trees in the manual. The issue is that there is not an inexpensive com box that I know of, most don't want to spend the 6 to 800 dollars.
 

firefinder

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Location
Macon,MO
Cable Configuration Update

I asked about the FMTV "Y" cable last week and received the attached wiring diagram. Can't answer whether the cable is the same for the M939A2 and FMTV.

Sorry, I didn't get this posted to the group earlier.

*****WARNING*****

JUST RECEIVED AN UPDATE - THIS CABLE CONFIGURATION IS FOR SOFTWARE UPDATING ONLY. PLEASE CONTACT STEELSOLDIERS USER - STELLAEVIL OR YOUR EQUIPMENT MANUFACTURER FOR ADDITIONAL INFORMATION BEFORE USING THIS CABLE CONFIGURATION.

*****WARNING*****

FMTV Harness.jpg
*****WARNING*****
 
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firefinder

Member
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Location
Macon,MO
Suprman,

Sorry, didn't receive any additional part numbers. Just the diagram. I am continuing to research part number for the FMTV "Y" cable also.
 

Coffey1

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Gray Court SC
Ok got the truck to quit dumping air buy changing the pcu.
But ecu and pcu are not communicating with each other.
Got one euc all it wants to do is flash it's 5 lights at me.
The other one won't do any thing at all but when I put in another truck it worked flawlessly.
 

Unclebigbad

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Nc
Our problem resulted in replacing the pressure switch on the 3rd tank with a switch that closes at 95lbs. Then the problem went away
 
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