M923A2 CTIS Problem

Stellaevil

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Michigan
No tires loose pressure with the plug off the ECU. If it was bad hub seal wouldn't that tire leak down? Going to pull the PCU, dismantle it and clean it up and see what happens.
The nice thing about the system is that nothing is pressurized when the system is not functioning. Only the tire hose is pressurized so the air seals have a much longer working life.
 

Suprman

Well-known member
Supporting Vendor
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The system does a pressure test to look for leaks and to determine tire pressure. If it senses high pressure it sends 12psi to hold open the wheel valves and dump. If the wheel valves dont have that continuous 12psi they will not stay open to dump. A bad hub seal will trick the pressure test but will leak when the pcu sends fill pressure so the wheel valves will end up seeing lower pressure than intended and will dump instead of fill.
 

Stellaevil

Member
99
12
8
Location
Michigan
The system does a pressure test to look for leaks and to determine tire pressure. If it senses high pressure it sends 12psi to hold open the wheel valves and dump. If the wheel valves dont have that continuous 12psi they will not stay open to dump. A bad hub seal will trick the pressure test but will leak when the pcu sends fill pressure so the wheel valves will end up seeing lower pressure than intended and will dump instead of fill.
This is partly correct: When the system pressure checks it cannot tell the difference between a low tire and a leak. It will only log a fault if an airline is completely disconnected and the reading is below 5psi. Any reading above 5 psi and it will just assume low tires and start inflating. Run Flat should be blinking so there will pressure checks every 15 seconds. When a pressure check opens the wheel valves, the tires will feed any leak between the valve and the QRVs. Only a leak big enough for the system to stall or loose air during an inflate will cause a fault to log.
 

Stellaevil

Member
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12
8
Location
Michigan
In case anyone is curious about my credentials and I am not trying to brag; I just want to help because I can. I started work for the original supplier of CTIS in their test lab. I moved with the business to the current company that produce this system. I have been the companies only CTIS application specialist for the last 10 years. I have personally built, tested, fixed, installed, and written the service manual on this system for 27 years now. When the military has a CTIS question it gets routed to me. The more I can help you guys out the fewer phone calls I have to answer. The updated manual has a lot of tips for troubleshooting problems when the vehicle is too old to hook up a laptop to. Thanks for you service!
 

Jbulach

Well-known member
Steel Soldiers Supporter
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Sunman Indiana
In case anyone is curious about my credentials and I am not trying to brag; I just want to help because I can. I started work for the original supplier of CTIS in their test lab. I moved with the business to the current company that produce this system. I have been the companies only CTIS application specialist for the last 10 years. I have personally built, tested, fixed, installed, and written the service manual on this system for 27 years now. When the military has a CTIS question it gets routed to me. The more I can help you guys out the fewer phone calls I have to answer. The updated manual has a lot of tips for troubleshooting problems when the vehicle is too old to hook up a laptop to. Thanks for you service!
I'll bet therooster2001 and 74m35a2 would love to hear your thoughts on the "M939 CTIS reprogram, Anybody done it?" thread!
 

Stellaevil

Member
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Location
Michigan
Welcome! We are proud to have you join this group!

Your expertise is a valued asset.
I am realizing that there are probably many CTIS threads that I don't know about that I could be of help with. Can someone here maybe start a new generic CTIS thread and I can try to answer any related questions all in one place. My designations for vehicles is different from the exact military system so here is what I refer to for CTIS programs. M939 (BMY), FMTV all variants, MTVR all variants, MATV, ASV All, International, FL-M917, Cougar, We did not do HUMVEE or Striker, JLTV but those are not available quite yet. There may be a kit available soon for higher pressure on FMTVs.
 

BlueSkyPIC

New member
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0
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Location
Miramar, FL
Hey guys,

I had my batteries disconnected charging since I hadn't ran the truck in 2 months. Once I reconnected the batteries I cant get the ECU to respond. No lights at all. The CTIS was working 2 months ago just fine. If I disconnect the ECU and then reconnect I get the over speed light and highway light on for a second and then nothing. ECU seems to have power but the buttons don't light up or do anything when pushed. Any ideas where to start? Batteries are good. New air dryer installed. Couldn't find anything in the tm for my situation.

Thanks

Bill
 

Stellaevil

Member
99
12
8
Location
Michigan
Hey guys,

I had my batteries disconnected charging since I hadn't ran the truck in 2 months. Once I reconnected the batteries I cant get the ECU to respond. No lights at all. The CTIS was working 2 months ago just fine. If I disconnect the ECU and then reconnect I get the over speed light and highway light on for a second and then nothing. ECU seems to have power but the buttons don't light up or do anything when pushed. Any ideas where to start? Batteries are good. New air dryer installed. Couldn't find anything in the tm for my situation.
Thanks Bill
Because it wowed when it powered on there are a couple of things to look for. First make sure the lights are not in "Blackout" Second If there is a PCU solenoid disconnected it is "no light Fault" Don't ask why, it may be to prevent circuit damage if there is a short.
 

74M35A2

Well-known member
4,127
193
63
Location
Livonia, MI
In case anyone is curious about my credentials and I am not trying to brag; I just want to help because I can. I started work for the original supplier of CTIS in their test lab. I moved with the business to the current company that produce this system. I have been the companies only CTIS application specialist for the last 10 years. I have personally built, tested, fixed, installed, and written the service manual on this system for 27 years now. When the military has a CTIS question it gets routed to me. The more I can help you guys out the fewer phone calls I have to answer. The updated manual has a lot of tips for troubleshooting problems when the vehicle is too old to hook up a laptop to. Thanks for you service!
Sweet. Your inbox will be full in 3...2...1...

Which CTIS control module do I need if I want to communicate with it using the Dana diag software? Easier to go by app vs part number, but both is best I presume. Have 1990 M925a2 right now, CTIS works perfectly, but will not communicate using the Dana specified interface. I made in inline harness which added comm terminals, which were not there in the factory truck side harness. This is actually the content of the other CTIS reflash thread in the 5t mod section. Pleasr and thanks. Apology if you already mentioned it.
 

BlueSkyPIC

New member
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0
1
Location
Miramar, FL
Because it wowed when it powered on there are a couple of things to look for. First make sure the lights are not in "Blackout" Second If there is a PCU solenoid disconnected it is "no light Fault" Don't ask why, it may be to prevent circuit damage if there is a short.
Not in blackout. How can I check if there's a PCU solenoid disconnected? I don't believe it's that but I'll check. Hoping for an easy fix but I'm thinking the PCU is bad.

Thanks Stellaevil for the help.
 

therooster2001

Active member
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Location
Colorado
There is an ohm test I believe to test connectivity to it. Should be in the TM. I might have a spare to test if you want. It was a take off, in unknown condition, but I bet working.
 

Stellaevil

Member
99
12
8
Location
Michigan
Yes, mine is like that. Thanks.
Download the manual from link posted on page 12, disconnect the ECU and ohm the solenoid sockets from the harness to a ground. Any open circuit is a problem I think you should get 60 ohms, just make sure they all read the same but not open. I you find an open disconnect the PCU and check it separately or the harness. Look for bent or pushed back pins.
 

IanW

New member
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0
0
Location
Indiana
Hey guys. New to the forum. I have a M923a2. We put 1600's on it. System worked fine, but one tire has a slow leak. I didn't drive the truck for a few weeks and the tire got pretty low (didn't check pressure). It would attempt to air it up for a few min, then I would get flashing lights. I read in this thread to press emer and run flat at the same time and it would pressure the tires down to the same pressure, then inflate them back up to whatever setting I choose. All the tires deflated, but now the system attempts to air them up, but fails to do so. I'll get a steady light on the emer and the mode I select. Anyone have an idea what is going on? Thanks in advance.
 

Andyrv6av8r

Well-known member
Steel Soldiers Supporter
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Location
Spartanburg,SC
Hey guys. New to the forum. I have a M923a2. We put 1600's on it. System worked fine, but one tire has a slow leak. I didn't drive the truck for a few weeks and the tire got pretty low (didn't check pressure). It would attempt to air it up for a few min, then I would get flashing lights. I read in this thread to press emer and run flat at the same time and it would pressure the tires down to the same pressure, then inflate them back up to whatever setting I choose. All the tires deflated, but now the system attempts to air them up, but fails to do so. I'll get a steady light on the emer and the mode I select. Anyone have an idea what is going on? Thanks in advance.
Just press Run Flat only at power up and see what it does. Bump your throttle up around 1000-1200 rpms also to supply enough air.
 

capnkirk

New member
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0
Location
Miami, OK
Just press Run Flat only at power up and see what it does. Bump your throttle up around 1000-1200 rpms also to supply enough air.
This is good advice. If your tires are super low and you have the option, I made a glad hand to female air tool quick connect to run tools off the truck. If you are close to shop air, make a male to make quick connect so you can back feed shop air to your truck. Tires will air up much faster than if you're just running of the onboard supply.
 
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