M923A2 CTIS Problem

1 Patriot-of-many

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Then you probably have a bad solenoid in the pneumatic unit. Fairly easy to replace. You'll have to remove the shield on the floor, disconnect the pneumatic unit from the two airlines and the electrical connection on the pressure switch. Could be the pressure switch too. Any way to replace the solenoids remove the bottom cover and test each solenoid, there are 3 of them. Splice in a new solenoid where one doesn't test good. I'm off the cuff here, don't remember what they should show as, do a search for Peter Paul solenoid on here otherwise send me a pm and I'll dig everything up. I've replaced a few.
 

Stellaevil

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good call. one tested at 47ohms and the other 2 tested open. ill see if I can run some of them down. thanks
If a solenoid is bad or "open" the ECU will fault out and turn off the the led indicators as soon as the ignition is turned on. If the highway led is blinking, when the supply tank reaches 115psi the system should do the first pressure check, if the 5L fault is then active it is because the pressure read too low. Maybe a dirty PCU cartridge and check the axle vent tubes during the "pressure check" (1.5 seconds) for air blowing out. This is an axle air seal leak.

There are 2 grounds on a M-939 PCU solenoid pack. See AXTS-0015 "2017" on Dana.com
 

74M35A2

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If a solenoid is bad or "open" the ECU will fault out and turn off the the led indicators as soon as the ignition is turned on. If the highway led is blinking, when the supply tank reaches 115psi the system should do the first pressure check, if the 5L fault is then active it is because the pressure read too low. Maybe a dirty PCU cartridge and check the axle vent tubes during the "pressure check" (1.5 seconds) for air blowing out. This is an axle air seal leak.

There are 2 grounds on a M-939 PCU solenoid pack. See AXTS-0015 "2017" on Dana.com
Added to friend list....
 

brazengoat06

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ok replaced the faulty solenoids and system functions. however it cant seem to inflate the tires. I do have a leaking wheel valve that will get fixed but also hear a lot of air movement in the rear hub area. cant tell if this noise normal or a hub leak. any tips?

also what fails in the wheel valves that cause them to leak? Oring?
 

Stellaevil

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ok replaced the faulty solenoids and system functions. however it cant seem to inflate the tires. I do have a leaking wheel valve that will get fixed but also hear a lot of air movement in the rear hub area. cant tell if this noise normal or a hub leak. any tips?

also what fails in the wheel valves that cause them to leak? Oring?
During an inflation check for air coming out the axle vent tubes, this is a hub air seal leak. The engine driven compressor has a very low output at idle so if you can run the engine at WOT when inflating. Wheel valves can be an old diaphragm or rusty seat that can be cleaned and the diaphragm can sometimes be oiled and massaged. If the system reaches Highway pressures and the valves won't close, the issue could be temperatures below 20F, you can loosen the WV lid screw a few turns and re-tighten and check that they now close. If they just leak down overnight check the internal seat.
 
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Tinstar

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I got tired of spending money on new parts and still chasing issues.
Finally threw in towel and installed Shrader valves in the wheel stems.
All manual now but no more ctis airing down tires, etc.

Will keep system installed and intact for future use.
 

therooster2001

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^^ That's a great way to stabilize it while still keeping things able to be used later / pick the problem back up later when you have time.

I understand the patience and money frustrations, but we have VERY knowledgeable CTIS people including a recent poster who IS the authority. My advice to anyone with a CTIS gremlin, is to stick with it. I can't think of few things cooler (yes maybe a bit extravagant, but so is the recent AC craze, and no pun intended there) than CTIS.

And not to get too preachy, but this is a solving forum. "We" even troubleshot the mystery issue from the guy who killed three engines in a row or the grinding transfer case. Yay us. Wes (Simp) routinely troubleshoots issues somehow while he's driving from the road for posters, and is like 99% correct (how does he do that anyway?) Smart mofo's on here. Someone even posted the manual CTIS plumbing valve option, go with that before giving up on CTIS. Encouragement to fix and learn drives this forum.

Some fool even thought he'd make a CTIS diagnostic monitor for us. Who was that guy anyways? Didn't Stellaevil already give that guy the right info to keep that project moving? Oh right.. "picking the problem back up later when you have time". I resemble that remark. Oh wait.
 

Stellaevil

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I cannot give advice on behalf of the company I work at for obvious legal reasons but I don't mind using my knowledge of the CTIS product to help everyone here. I have 27 years on all US based military vehicles using the Eaton/#### systems. Mechanical and electronic test lab technician to applications engineering. As these threads continue to expand I will continue to post the AXTS-0015 (2017) Troubleshooting Guide. Just Google it. Parts can be very expensive so identifying the problem is critical.
 
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brazengoat06

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Can't get may system to inflate past 28 psi. Then as the system shuts off the left front bleeds down to 18psi. I rebuilt that air valve with no resolve. I do have a rear axle hub leak, is that enough to prevent inflation past 28psi?
 

Andyrv6av8r

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Can't get may system to inflate past 28 psi. Then as the system shuts off the left front bleeds down to 18psi. I rebuilt that air valve with no resolve. I do have a rear axle hub leak, is that enough to prevent inflation past 28psi?
Take a pair of Visegrips and pinch that hub supply line off to see if it fixes your problem.
 

Stellaevil

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Can't get may system to inflate past 28 psi. Then as the system shuts off the left front bleeds down to 18psi. I rebuilt that air valve with no resolve. I do have a rear axle hub leak, is that enough to prevent inflation past 28psi?
If you are inflating at idle, yes a hub leak can be a problem. It is recommended to inflate at full throttle when possible. If a wheel valves will not close at 28psi the valve diaphragm may be bad but it would have to be really bad or very hard. More likely it could be a restriction in the Hub or air lines from the hub to the QRV. Remove the wheel valve control line from the hub and blow compressed air through it If it is not blowing out the QRV snorkel freely then that is a problem.
 

Stellaevil

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Updated Troubleshooting Guide
FMTV Wiring was not correct.
[h=1]Forum: Technical Manuals[/h]https://www.steelsoldiers.com/showthread.php?175911-Central-Tire-Inflation-System-(CTIS)-AXTS-0015-2018
 

galaxie428

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Hi all. I have had my M923A2 for a little over 4 years with a perfectly good working CTIS. Recently I started getting the 5 lights flashing after some time of the system trying to fill up. It is too cold out to try to do much trouble shooting right now but I did take the truck for a drive yesterday. I aired down to emergency while slowly driving on the back roads. Once it aired down to emergency, no flashing lights. I aired up to x-c and once it hit it, no flashing lights. I put it back on hwy and got the 5 flashing lights again. I checked the tire pressure with a gauge when I got home and both the front and middle axle tires were all at 50PSI, the back axle, both tires were at 40 PSI. I also noticed that the quick release valve on the drivers side rear over the rear tires was leaking what seems like a significant amount of air out of the port that has a dust cover on it. The dust cover is dry rotted but not sure that really matters. If it ever warms up a bit, I would like to start troubleshooting and fixing this. Thoughts on where to start? Thanks.

exhaust valve.jpg
 

Stellaevil

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Remove the the duckbills from the the QRVs see if that fixes the issue. They need to be open to properly close the wheel valves.
5 lights on power up; Electrical issue
5 lights after the first pressure check; large air leak, check the axle vents for the seals leaking.
5 lights after the system has inflated for a while. Inflate at high idle or full throttle.
 

crzyxj

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Our 923 just flashes one light and never does anything else. I cannot figure it out. the pressure sensor on the wet tank is working and it only once flashed all 5. I am not hearing the pressure check clicking and cannot find a leak, I do have one brake actuator leaking and thats it. Primary tank is always at 95psi and secondary is at 120. Any ideas, I have tried everything on this post other than swapping parts
 

74M35A2

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If you hear no solenoid clicking, then it is waiting for system air pressure to reach 100psi. As the sensors age, this slips. Set your truck air pressure to 120psi, and try it. Most of these truck will not be able keep up with filling at an idle, bit will do it quickly at speed.
 
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