M1078 fmtv ctis

[No-0ne]

Brand new to the forum. I’ve been searching the forum for days and haven’t found my exact problem discussed so I figured this is as good as any of the other posts to ask for help. I have a 2005 SS M1088A1 rebuilt by ACELA in 2019. It’s been sitting near the coast for 5 years. Like an idiot I thought I could get in it and drive it home to Utah. Now I’m stuck in Johnson City TN waiting for a transport to ship it home. One of the issues that has me shipping it home is the CTIS isn’t working properly. When I start the truck the HWY light flashes as it fills the front tires (all 4 rear tires are holding full pressure consistently). It seems to take quite awhile but eventually the lite will go solid when the tire pressure reaches about 75 PSI. But the like only stays solid for maybe 1 min probably less and then it flashes again for a long time before it goes solid for another short period and repeats the cycle again. I’ve tried unplugging the ECU once the lite goes solid to see if the tires will stay at pressure and they won’t. They (both front tires) drain down to 45 psi in a mater of about 20 min or so And then hold tight at 45 psi. Again the rear tires stay at full psi. What can be going on? I can’t hear any leaks. I’ve sprayed soapy water all over the wheels and wheel valves and nothing. And if there was a leak why would it always return to 45psi. Is this an issue with the front axle quick release valve?

 

[GeneralDisorder]

Brand new to the forum. I’ve been searching the forum for days and haven’t found my exact problem discussed so I figured this is as good as any of the other posts to ask for help. I have a 2005 SS M1088A1 rebuilt by ACELA in 2019. It’s been sitting near the coast for 5 years. Like an idiot I thought I could get in it and drive it home to Utah. Now I’m stuck in Johnson City TN waiting for a transport to ship it home. One of the issues that has me shipping it home is the CTIS isn’t working properly. When I start the truck the HWY light flashes as it fills the front tires (all 4 rear tires are holding full pressure consistently). It seems to take quite awhile but eventually the lite will go solid when the tire pressure reaches about 75 PSI. But the like only stays solid for maybe 1 min probably less and then it flashes again for a long time before it goes solid for another short period and repeats the cycle again. I’ve tried unplugging the ECU once the lite goes solid to see if the tires will stay at pressure and they won’t. They (both front tires) drain down to 45 psi in a mater of about 20 min or so And then hold tight at 45 psi. Again the rear tires stay at full psi. What can be going on? I can’t hear any leaks. I’ve sprayed soapy water all over the wheels and wheel valves and nothing. And if there was a leak why would it always return to 45psi. Is this an issue with the front axle quick release valve?

If both front tires, but ONLY the front tires, are losing air down to 45 psi then the problem is likely one of the two wheel valves on the front wheels.

You can disconnect the wheel valve banjo bolt and zip tie a vinyl glove over the hose and see if it fills up the glove. That would indicate a leaking wheel valve diaphragm.

Once you find the leaking wheel valve just get a longer screw that's the same size and thread pitch as the phillips screw in the center of the wheel valve and thread it in till it forces the diaphragm shut or move the shrader core to the valve stem instead of the inflation nipple in the wheel valve and inflate that tire manually to whatever you like.

 

[No-0ne]

Thanks GeneralDisorder! Is the shrader valve at the fill point on the wheel (not the one on the wheel valve itself) a standard shrader valve? Does it have a valve core in it? I thought about doing as you suggest but I thought I read somewhere that there is no core in it and that it an odd size that can;t be filled with a typical air chuck.

 

[GeneralDisorder]

The Shrader core itself is the same as any other tire on a passenger car and fits both locations. You can remove the one from the wheel valve and install it into the valve stem. The valve stem has a slightly different connection but *most* adapters will work you just have to hold them as the valve stem doesn't have the threads they are expecting to grab onto. Occasionally you run into one that won't go on without a fight - just find another brand or model. Most of them work you just have to be smarter than a potato.

 

[Ronmar]

What general said. You will have to remove the elbow fitting on the small hose where it connects to the stem pipe that is bolted to the wheel. Looks like a standard Schrader core in the wheel stem.

you could also remove the cover screws on the wheel valve, there is a spring and a diaphragm inside, the inner center of the diaphragm seal the air in the tire, and there is usually debris or corrosion there allowing the tire air to leak away… sometimes for valve case screws snap, so putting a schrader in the wheel stem pipe is your fallback…

is this the only thing keeping you from driving?

 

[Third From Texas]

Yeah, it's obviously not the CTIS controller itself.
Unplugged, the tire pressure should hold whatever the pressure is set for indefinitely.
*also note that you can fry the controller plugging/unplugging it while it's power supply is hot so always be sure all power is off before plugging/unplugging it

So as others have stated you have a hardware leak either at the wheels, axel, fitting, valves, etc.
Isolating each tire from the systems and you should be good to drive with the controller disconnected.

 

[GeneralDisorder]

Yeah, it's obviously not the CTIS controller itself.
Unplugged, the tire pressure should hold whatever the pressure is set for indefinitely.
*also note that you can fry the controller plugging/unplugging it while it's power supply is hot so always be sure all power is off before plugging/unplugging it

So as others have stated you have a hardware leak either at the wheels, axel, fitting, valves, etc.
Isolating each tire from the systems and you should be good to drive with the controller disconnected.

To the power supply comment - very useful to wire in the optional CTIS OFF toggle switch that the harness and annunciator panel are already setup for. This way you can easily reset the controller or just fool it into holding some random pressure. Tell it to inflate to the moon and just toggle it off when you get to the pressure you want. Can even drive while letting it deflate till you find the best pressure for your speed and tires and then just kill the power to the controller.

 

[No-0ne]

Thanks everyone, for your input! Well I got in the truck and drove it to the parts store to get some penetrating oil to start the process of loosening up the screws so they don’t break off when I go to replace the diaphragm in the wheel valves. Miraculously the CTIS aired up the front tires and then the light held solid. So I decided to go for it and start the long drive home. The light held solid for about 4 hours and then started blinking. It never stopped blinking the rest of my 15 hours of driving. I made it from Johnson City TN to Bentonville AR. I came out this morning to find the the front tires low and now one of the rear tires completely flat! But just one. As suggested in an earlier commen, if it’s the wheel valve the opposite tire should be deflated also? Or do both front tires and now one rear tire have bad wheel valves?

I’m registered Commercial because I’m Turing this truck into a Septic Pump truck. So I have to go through every weight station. I’m worried about getting red tagged out in the middle of nowhere if the shut me down to do an inspection and my tires start going flat.

Am I at risk of causing more issues or problems with the system, running it for so long with the lights blinking and constantly filling tires? Am I going to burn up the control module?

Should I do a rebuild on all the wheel valves? Do you think that would solve my issues or are my problems with other component? Has anyone tried either of these kits? Would either one of these work?

https://www.danaaftermarket.com/spicer-commercial-vehicle/commercial-axle/tire-systems/part/Ctis%20Wheel%20Valve%20Upgrade%20Service%20Kit/505295?cp=1&catalog=PIMS_NA&partType=PART

Eaton Kit-Repair Wheel Valve P/N: 599913

599913 Eaton Kit-Repair Wheel Valve. We have Eaton differential parts, new in box in stock and ready to ship worldwide.

www.pgttruckparts.com

 

[Ronmar]

low tire = wheel valve, so you have 3 leaking wheel valves. They may have bad diaphragms, but they may simply be dirty and unable to seal...

you can take all the wheel valve plumbing off the wheels and run schraders in the stem pipe and not worry about it, but the wheel valves are easy enough to work on and quite reliable once you get them cleaned up and the system cycles them regularly.

that is the usual issue with CTIS, leakage in the system somewhere causing flashing lights, or the controller itself simply fails...

 

[GeneralDisorder]

You should rebuild the wheel valves - DO NOT buy the Chinese one's from Midwest Military. Only buy genuine Dana/Spicer/Eaton parts.

Then you should rebuild the PCU under the driver's side dash. Those two items - wheel valves and PCU - will cover 90% of the problems people encounter with the CTIS.

You can manually inflate the tires and disconnect the controller, or leave it in semi-fault mode if you like. The controller doesn't care what mode it's in or how long it's in fault vs. normal operation. It's normal for it to be ON at all times when the vehicle is running and it's a computer - it doesn't care (for the most part - not getting into the weeds of MTBF for driver MOSFET's, and other obscura) - what function it is performing - it's power draw is the basically the same regardless of what it's doing.

The wheel valve diaphragms are frequently the biggest source of problems due to their environment and being largely ignored unless they malfunction. Be CAREFUL taking out the cover screws. Hit them with a punch, and some penetrating oil, and then use a torch on them. They rust to the alloy housing and if you just start turning them they snap off at about a 50% rate. Removing tiny rusted fasteners like this is an ART FORM so if you know some old grey beard that is tuned up for that purpose like some of us around here are - please ask for help and advice. These are no joke they WILL break and you'll not have fun trying to chew a steel bolt out of an alloy housing after the fact.

 

[No-0ne]

What general said. You will have to remove the elbow fitting on the small hose where it connects to the stem pipe that is bolted to the wheel. Looks like a standard Schrader core in the wheel stem.

you could also remove the cover screws on the wheel valve, there is a spring and a diaphragm inside, the inner center of the diaphragm seal the air in the tire, and there is usually debris or corrosion there allowing the tire air to leak away… sometimes for valve case screws snap, so putting a schrader in the wheel stem pipe is your fallback…

is this the only thing keeping you from driving?

View attachment 941521

As far as what’s keeping me from driving, there’s this issue with the CTIS and now I have a Air dryer with the heater unplugged because the mechanic put a air dyer with a 12V heater on it. DOT inspectors don’t like to see things unplugged. I have the same concern with disconnecting the CTIS. I don’t think DOT is going to like seeing a wheel hose disconnecte. Probably be ok if I was able to remove the whole system and plug where the banjo bolt is for the air coming from the axle. Anyone know what size plug I would need?

 

[No-0ne]

Thanks again! Are those kit links I referenced the right ones?

 

[GeneralDisorder]

As far as what’s keeping me from driving, there’s this issue with the CTIS and now I have a Air dryer with the heater unplugged because the mechanic put a air dyer with a 12V heater on it. DOT inspectors don’t like to see things unplugged. I have the same concern with disconnecting the CTIS. I don’t think DOT is going to like seeing a wheel hose disconnecte. Probably be ok if I was able to remove the whole system and plug where the banjo bolt is for the air coming from the axle. Anyone know what size plug I would need?

You don't need anything to remove the wheel valve except an allen socket for the valve, a crescent wrench for the banjo and a Shrader tool. You simply remove the entire valve and hose assembly and install the shrader directly into the valve stem. You can leave the lug nut open to the elements for a short time. The hollow lug nut should be plugged eventually. Probably a rubber plug from the hardware store would work for the short term. It's a weird straight pipe thread that it uses on that banjo - it's not something you will find but they can be made. Remove the controller and tuck the wiring under the dash. The inspectors aren't looking for the truck to have CTIS since that's a military feature. With the wheel valves and hoses removed and the controller not present they aren't going to see anything that will raise an eyebrow,

 

[GeneralDisorder]

Thanks again! Are those kit links I referenced the right ones?

Not sure on that but I doubt it. There's WAY more part numbers for various wheel valve types than you probably are aware of. The CTIS system went through decades of design and development and many different variations. Many of the alloy wheels have the wheel valve literally built directly into the wheel casting so Hutchinson was also involved. Without pictures and without cross-referenceing the part number I can't say for sure, but if that's just some random wheel valve kit you found on google the chances of it being the correct kit are about 3%

 

[Ronmar]

If I recall the banjo bolt is an 18MM x 1.5MM pitch(I can confirm that when i get home). That metric pitch actually coincides with a standard pitch bolt, as that has been the root cause of a few CTIS problems I have helped troubleshoot over the years. on these problems, someone had threaded a standard solid bolt in where the hollow banjo bolt is supposed to be, cutting off the air connection to that wheel and creating inflate and deflate issues...

 

[No-0ne]

I tried removing the wheel valves today and putting a valve core in the shrader valve so I could air it up but the valve core wouldn’t seat deep enough. The nipple stuck probably 1/8” out of the stem. I event took the core out of the stem on the wheel valves itself and tried using it but same fit. I tried trimming the nipple back till it was flush with the valve stem but the air chuck wouldn’t seal against that valve stem well enough to put air in the tire.

Is there a different type of valve core that fits this stem?

 

[GeneralDisorder]

Nope. I've done that hundreds of times and never had an issue. Go get some new cores I guess. Could be a defective valve stem I guess. Have to dismount the tire to replace that.