CTIS hwy blinks again after 30 seconds

[Plasa]

Hello forum.
I know that there are a lot of CTIS threads, but I didn't found any usefull info, probably because I am blind... Sorry about it

I have a M1078 with CTIS partially working. I will try to explain what happen:
- Air tank is full at 120psi
- CTIS starting to work (hwy blinking)
- I hear that the tires are inflated (no air leak, but small flapping noise from the quick release valve?)
- sometimes it is interrupted (due pressure check)
- goes on for about 5 minutes
- ctis stops inflating and vents the tubes (the "hiss" in front)
- ctis hwy light is steady
- front quick release valve is venting about 10-15 seconds, then stops (like a italian mocca coffee machine )
- CTIS is doing the 30 second test (blinking again)
- CTIS starts all cycle again

What I checked:
- wheel valves are OK, they do not loose air. I loose the banjo bolts and hear no sound
- all tire pressure are 90 psi. Probably because of a change of the ECU.
- pressing another terrain button deflates. I didn't wait to see deflating the tires but both quick release valves are venting...
- I had a massive air loss in front wheel valve, change the diaphragm and now keeps the air.

It is normal that after inflating cycle and venting the quick release valve open for 10 seconds?
Can be that the from QRV have an issue?
Can be dangerous having 90 psi on a m1078?

Thanks and regards from Italy

Christian

 

[319cssb]

Sounds like a leak in one of the air hoses to the wheel

 

[Suprman]

Sounds like a hardware issue. If the system fills and is at highway pressure and tben a few seconds later it does a pressure test and thinks you need more pressure. The ecu could be programmed for higher pressure or it could be that high due to
a fault and the system thinks there is less. The excess coming out the qrv at the end of a cycle would be increased with the higher pressure.

 

[Ronmar]

If they vent at all, the QR valves should only vent very briefly. When the control valve solenoid on the PCU is released by the processor, it should open fast and quickly vent the air in the system so it passes the QR dump point of 10-15 PSI as fast as possible. If it is not releasing/venting quickly. A slow decrease in pressure past the QR dump point would cause them to open for an extended period untill the pressure finally drops low enough to close the QR’s. So maybe a sticky control valve or a clogged vent pipe? The PCU comtrol valve vents into the lower cover on the PCU that covers the solenoid valve coils. That cover is connected to a hose that connects to the floorboard port and dumps the air outside behind the grill.

There are max tire inflation pressures specced in the manuals... the tire manufacturers also specify max inflation pressures.

 

[coachgeo]

Suprman alluded to this....... It could it be possible you have ended up with a MTV CTIS computer? they run up to 85lb I believe so getting by error to 90lb may be in that computers margin of error. If that is the case consider yourself lucky. Is it to high? what is your load? what tire are you running?

Pull numbers off the ctis unit and report back here with them.

 

[319cssb]

@Plasa
read in the m1078_TM 9-2320-365-20-2 page 2-1856 and on as I mentioned before the TM hints to a air leak.
http://www.emilitarymanuals.com/pdf/M1078/TM9-2320-365-20-2.pdf


In my 1089 5 ton MTV I had the problem of the truck not being able to hold the tire pressure, as a result it would recycle all the time trying to get the pressure to 85psi. What fixed it in the end were new wheel valves as the rubber membrane inside was worn and would not hold the tire pressure as regulated.
Hope this will help you. But most importantly read the TM troubleshooting procedure and follow it. This is how I solved my CTIS issues

 

[Plasa]

Hello all!
Thank you for your infos.

@coachgo: I have Goodyear MV/T tires, weight is about 19.800 lbs (9000kg).

I untighten the banjo skrews and seems no wheel is loosing air. But today I will make the soap water test.
I'm quite sure that the ECU is not original, it was replaced from another truck. I will ask the vendor what truck was, and write down the numbers on the actual ECU.

The control valve solenoid release quickly, a short and loud hiss. But after that the quick release valve continues to vent for about 10 seconds. Can be that 10 seconds are enough pressure loss that the entire system recycle again? When inflating no air loss on the quick release valve...

Can be that the pressure sensor on the PCU is faulty and sends wrong pressure to ECU? That can be the source why it's always inflating, and why it's always recycling... Is there a possibility to check it? I have no Y cable so no DDT. Just multimeter....

Thank you very much for helping me out!

Christian

 

[Plasa]

Hello again.
I'm now quite sure that the ECU is from a FMTV 5 ton truck. That can explain why the pressure is so high.
Are the ECU compatible with the original pressure transducer on the PCU? If I change the pressure transducer on the PCU, makes diffrence?
It's possible to change pressure settings? I read on other threads that settings depends on 2 pins (high, float, ground), but maybe they are set inside the ECU?

Thank you very much and sorry for all the questions...

Christian

 

[319cssb]

The ECU can be reprogrammed. But on the original (A0) truck it is very difficult. On A1 trucks it can be done with a laptop, the 'Dana diagnostic tool' software and a dearborn adaptor. There you just plug the laptop in change the target tire pressure and save.
But even if the pressure is too high, it should be able to hold that pressure. I think the secret lies with a faulty valve.


you could connect shop air to the truck. That way you can energize the ctis without running the engine, which makes spotting air leaks a lot easier

 

[Plasa]

Yes, I use shop air to the truck. Today I need to recheck it again. I untighten the banjo skrews, let's see if some tire has diffrent pressure...

Thank you very much!

Christian

 

[Plasa]

Hello again.
Now I am quite sure to found the reason. I gave a look to the ECU and as immagined it's not original. I did the following tests:
- deflate to cross country: works well, stops at 60psi and stay stable
- deflate to sand: works also, stops at 40psi and stay stable
- inflate again to cross country: takes about 20 minutes, but inflates again to 60psi and stays stable. 30 second test is correct and tubes vent correctly.
- shotdown and restart CTIS, system did the pressure test and works like a sharm.

But the highway pressure cannot be used, it's too high (90psi), so I think that the ecu is not compatible with the other components.
I attach a picture of the ecu. It is much older than the vehicle and not sealed, the electronic parts can easily changed, no gel inside.

Is there a way to change the pressure transducer or put some resistance between ecu and transducer to get the correct psi value, or it's better to change entire ecu?

What I've learned is that even if the seem identical, pay attention what type of ecu you have. I think running entire system with 90psi can create some serious damage...

Thank you!

Christian

 

[coachgeo]

...

But the highway pressure cannot be used, it's too high (90psi), so I think that the ecu is not compatible with the other components....[/IMG]

Gesendet von meinem EVA-L09 mit Tapatalk

the M1078's ctis programed military PSI is for ability to jumping from "on road" to "off road" quickly. For majority of highway use it is way to low. Leads to excessive tire wear spongy ride. If yours is NOT an air problem but actually an MTV controller You will find many with an LMTV want exactly what you have; a MTV CTIS controller for their LMTV, especially if they are looking toward an Overland Camper build!!! Simply put the higher psi like you have is better for highway use. The MTV tire you run is Max at 100psi if I am not mistaken. Im betting your tires will settle out around 80psi.

Compromise.... With Power off...... just unplug your ctis. Set pressure to where you want with a tire gauge. Once a Month plug it back up and restart truck and let it do its thing. Turn off truck and repeat.

PS- if you use tapatalk to load pics... ASAP go back and use the link they provide to load your picture to the bulletin board instead of leaving them hosted by tapatalk.

 

[Plasa]

Hello Coachgo!
I verify the pressure and in fact is above 90 psi. Main problem is that the ctis does not work with this pressure, continue to inflate, recycle everytime, pressure test after 30 seconds is always negative, so starts again to inflate.

What should be possible is to insert a resistance (maybe a potentiometer) to rise/lower the voltage of the transducer signal. but without exact specs it's a trial and error. and can be a expensive trial error game

 

[coachgeo]

Hello Coachgo!
I verify the pressure and in fact is above 90 psi. Main problem is that the ctis does not work with this pressure, continue to inflate, recycle everytime, pressure test after 30 seconds is always negative, so starts again to inflate.

What should be possible is to insert a resistance (maybe a potentiometer) to rise/lower the voltage of the transducer signal. but without exact specs it's a trial and error. and can be a expensive trial error game

sounds like you determine the pressure you are getting is due to other issues so may/may not be an MTV controller. In that case do as others have suggested and trouble shoot further before worrying about modifying controller. The Technical Manuals aka TM's (repair, maintain, driver) can be found here. There is also lot of discussions in here on CTIS and several have links to the manual for troubleshoot of the controller.

PS.... much thanks for uploading your pic direct to this board now. Helps the archives stay helpful for many years to come.

 

[Plasa]

sounds like you determine the pressure you are getting is due to other issues so may/may not be an MTV controller. In that case do as others have suggested and trouble shoot further before worrying about modifying controller. The Technical Manuals aka TM's (repair, maintain, driver) can be found here. There is also lot of discussions in here on CTIS and several have links to the manual for troubleshoot of the controller.

PS.... much thanks for uploading your pic direct to this board now. Helps the archives stay helpful for many years to come.

Yes you are right, but strange thing is that ctis don't work only with the 95psi pressure. I am scared about the high pressure, on front tiresbI got 95 psi, and max psi for tire is 95. I would be more than happy if pressure is around 75/80 psi, but staying so near on max is scaring me...
What I am thinking is to let it be like now and not use the highway terrain. But I don't like half working systems...

Thank to you for the great support you give to me and all others! This is a great forum!

Christian

 

[319cssb]

@plasa you're welcome. I am glad Suprman and I were able to point you in the right direction.

 

[coachgeo]

@plasa you're welcome. I am glad Suprman and I were able to point you in the right direction.

At lease now for sure he wont be on a wild goose chase, trying to chase down problems..... that were potentially not problems..... just an MTV controller doing what it is supposed to do. Too bad that is not the case as it appears to be like yall surmised earlier. It will be an advantage if he is lucky enough to have got an MTV controller on her.

While he chases symptoms and solutions via TM's etc. maybe someone will pipe in who has the right knowledge to identify which controller he as via pic he posted. Will help in his troubleshooting as he seeks and fixes leaks and/or bad valves etc. Steady 60psi on cross country still sounds MTV-ish. Will be interesting to see what each ctis selection puts psi at once leaks/valves issue are fixed.

 

[coachgeo]

...
What I am thinking is to let it be like now and not use the highway terrain....

Until you get time to dig into it further.... set it to whatever gets you close to pressure you want to drive at.... turn off truck then unplug cable from side of the unit in the cab.

 

[Plasa]

Until you get time to dig into it further.... set it to whatever gets you close to pressure you want to drive at.... turn off truck then unplug cable from side of the unit in the cab.

The pressures are:
highway: 95psi, tires don't loose air, but CTIS continues to inflate.
cross country: 60psi, working perfect
sand: 40psi: working perfect

So I also think it's a MTV ECU, but I don't know if I should happy or not...

I don't know if all the components (wheel valve, PCU, QRV etc) are made for this high pressure or they get damaged when I let the tires inflate so much...

I am also trying to use the truck as a overland camper...

Nearly 1 year that I am working on it, but I got the truck only 2 month ago...
Christian

 

[coachgeo]

whomever did the interior of both cab and rear habitat did an awesome job. Would love to see more. Curious of your rear bumper too.

As to MTV CTIS valve causing issues with other components..... have not heard/seen a mention that valves used are any different between the LMTV's and the MTV's. Pretty sure it is all same valves so once you're all repaired in leaks and valves, if it is an MTV controller you should be fine in that respect.

Others with more knowledge will chime and and clarify though.