M35A3 CTIS MANIFOLD PSI 1-3

[SniperCow]

I have a m35a3. ON THE PCU SCREEN IT SHOWS FLAT BLINKING AND WHEN IT TRIES TO SENSE/ADJUST, IT DISPLAYS MANIFOLD PSI 1-3. WHEN IT PERFORMS THIS OPERATION IT DROPS THE AIR PRESSURE FOR THE ENTIRE VEHICLE SYSTEM DOWN TO 90 psi AND IT STOPS WHEN IT HITS 90.

the tires hold air for days. I’ve reduced all tire air pressure to 20 psi. It does NOT fill them back up. The system has a slow leak in the transmission shift tower, other than that all is quiet and sealed well.

very little oil slime residue in the ports on the manifold.

I’ve read 2 threads that have zero responses on this exact situation. I’ve posted on those threads also.

 

[Wondering_Alaskan]

I have a m35a3. ON THE PCU SCREEN IT SHOWS FLAT BLINKING AND WHEN IT TRIES TO SENSE/ADJUST, IT DISPLAYS MANIFOLD PSI 1-3. WHEN IT PERFORMS THIS OPERATION IT DROPS THE AIR PRESSURE FOR THE ENTIRE VEHICLE SYSTEM DOWN TO 90 psi AND IT STOPS WHEN IT HITS 90.

the tires hold air for days. I’ve reduced all tire air pressure to 20 psi. It does NOT fill them back up. The system has a slow leak in the transmission shift tower, other than that all is quiet and sealed well.

very little oil slime residue in the ports on the manifold.

I’ve read 2 threads that have zero responses on this exact situation. I’ve posted on those threads also.

How did you get your CTIS system to pump up to 90PSI?? Mine is capped at 45PSI for highway... I have been trying to look into reprograming it pump up to 60psi as the wheel seals are rated to 65PSI on the stock A3 wheels, but have had no luck finding that information and am starting to look at a manual system I can build and install myself.

That all being said, I am currently having the same issue (although mine bounces from 3-5psi with flashing FLAT code) and I found that you could have an internal leak in the hub assembly at the quad seals or the bearing O-rings. From what I read, this will cause the flashing "flat" code, but without losing air pressure in your tires (depending on the bad seal). It should cause the air pressure to drop slowly in the air line though when it remains pressurized after turning off the truck. You will NOT be able to hear this leak with everything turned off and the wheel on the truck. You must dig into it and hunt down which wheel is causing the issue. That is what I gathered anyways. On that same thread I also read a bad axle flange cap can cause the issue as well if the outer bearing O-Ring is bad. Basically, a whole lot of dig in and see whats up.

EDIT: Just realized this post is over a year old. If you happen to read this, did you ever solve this issue? I'd love details if so.

 

[HDN]

How did you get your CTIS system to pump up to 90PSI?? Mine is capped at 45PSI for highway... I have been trying to look into reprograming it pump up to 60psi as the wheel seals are rated to 65PSI on the stock A3 wheels, but have had no luck finding that information and am starting to look at a manual system I can build and install myself.

That all being said, I am currently having the same issue (although mine bounces from 3-5psi with flashing FLAT code) and I found that you could have an internal leak in the hub assembly at the quad seals or the bearing O-rings. From what I read, this will cause the flashing "flat" code, but without losing air pressure in your tires (depending on the bad seal). It should cause the air pressure to drop slowly in the air line though when it remains pressurized after turning off the truck. You will NOT be able to hear this leak with everything turned off and the wheel on the truck. You must dig into it and hunt down which wheel is causing the issue. That is what I gathered anyways. On that same thread I also read a bad axle flange cap can cause the issue as well if the outer bearing O-Ring is bad. Basically, a whole lot of dig in and see whats up.

EDIT: Just realized this post is over a year old. If you happen to read this, did you ever solve this issue? I'd love details if so.

There are four seals involved in the hub CTIS, and they're all part of the quad seal: An o-ring on both the inner and outer bearing, and a ridged (it has an X-shaped cross section) in each of the bearing cups where the bearing bores protrude. The flange cap or flange gasket shouldn't affect CTIS as long as the outer quad seals are good. And yes, you definitely have to disassemble the hub to get to the seals. The seals have to be removed anyway to pack the bearings, except perhaps the bearing cup seals, unless they pop out during the job I suppose.

I'm not sure where to find good quad seal replacements. The last ones I got from Big Mike's had good o-rings, but the X-shaped cross section seals weren't the right diameter - they were too small. I actually destroyed a couple trying to drive the inner bearing into the hub because the inner bearing bore sheared a chunk off them. I ended up reusing the old bearing cup seals, but I don't run CTIS on my truck right now, so I'm not very concerned about their performance.

It was pretty cool learning how the CTIS works on the A3, seeing how air gets from the truck to recycled modified A2 axles and in through the special inner bearings and to the hubs, but it is definitely maintenance-intensive.

I'm not sure if it's possible to re-program the CTIS computer. I don't see anything in the manual about it. The few guys who have A3s on here with working CTIS just manually inflate the tires to the pressure they want if they want to go above 45 PSI.

 

[Wondering_Alaskan]

There are four seals involved in the hub CTIS, and they're all part of the quad seal: An o-ring on both the inner and outer bearing, and a ridged (it has an X-shaped cross section) in each of the bearing cups where the bearing bores protrude. The flange cap or flange gasket shouldn't affect CTIS as long as the outer quad seals are good. And yes, you definitely have to disassemble the hub to get to the seals. The seals have to be removed anyway to pack the bearings, except perhaps the bearing cup seals, unless they pop out during the job I suppose.

I'm not sure where to find good quad seal replacements. The last ones I got from Big Mike's had good o-rings, but the X-shaped cross section seals weren't the right diameter - they were too small. I actually destroyed a couple trying to drive the inner bearing into the hub because the inner bearing bore sheared a chunk off them. I ended up reusing the old bearing cup seals, but I don't run CTIS on my truck right now, so I'm not very concerned about their performance.

It was pretty cool learning how the CTIS works on the A3, seeing how air gets from the truck to recycled modified A2 axles and in through the special inner bearings and to the hubs, but it is definitely maintenance-intensive.

I'm not sure if it's possible to re-program the CTIS computer. I don't see anything in the manual about it. The few guys who have A3s on here with working CTIS just manually inflate the tires to the pressure they want if they want to go above 45 PSI.

There are good quad seal replacements (and all the other parts, except the keyway gasket, which you can just use silicone gasket maker) all over the place. eBay, Big Mikes I think still has them, Oshkosh has them, Boyce Equipment, and quite a few more. Even the retainers are popping up more and more and readily in stock in many places. I just rebuilt one of my hubs up front about 2wks ago and I was able to source all the parts without issue. I destroyed my first inner bearing o-ring too. You have to be incredibly gentle and move slow over the spindle threads. lol

Whoever touched my truck I bought last though skipped soooooo many steps in the rebuild, it makes sense why my CTIS isn't functional at the moment. No sealant between the spindle & knuckle, no quad seals or retainers installed, and no sealant for the key-way or between the mating surface of the bearing races & hub assembly. I'm shocked my wheel stayed on for the 8000 miles I put on the truck till I finally blew the wheel bearing on that side. lol I'm in the process of pulling off every wheel and hub assembly, tearing them apart, and rebuilding. If they skipped all that on one wheel, chances are the rest are trash too. Going to be spendy, but I am looking forward to getting my CTIS functional again as I daily drive my A3 and go offroad, camping, road trips, etc in it.

I think that's what I am going to have to do with my CTIS to go above 45psi. I found the thread to build a manual manifold and saw it can work in unison with the CTIS computer from CM automotive. Hoping to put that together once I get my hubs rebuild with all the proper parts. lol I know you can reprogram the ones in the Stewart & Stevensons & some of the 5tons that run the same system, but I have yet to find anything on this and CM Automotive seems to be out of business, or their website is dead at least to try and reach out to them about it.