CTIS bench test harness

[Lostchain]

CTIS is one of the coolest features on our trucks. I’ve been wanting to make a bench testing harness for quite some time, and I finally got around to it. It’s part of the forum lore around here that the controllers are unreliable. In practice I think they are extremely robust. I bought a pile of “bad” ones off eBay and so far they are function checking perfectly. It amazes me how many of them have stored codes for all kinds of wiring issues. Similar to my testing with the 100a alternators, it seems like a very large portion of “bad” units are suffering from terrible in-truck wiring issues, and actually have no problems whatsoever.

Anyways I’m having fun with it. It has J1939 and J1708 support and a switch to simulate the tank pressure switch. I would like to add a small pressure tank to test that PCU solenoids are strong enough to hold pressure and don’t leak.

 

[Keith Knight]

Interesting, so what do you mean by bad wiring? And how would it affect the CTIS.
9 years ago when I purchased my 2003 A1 the CTIS controller was bad, purchased a new one and never had another problem with the controller. Never having wiring problems but many different electrical components have failed.

 

[Lostchain]

Interesting, so what do you mean by bad wiring? And how would it affect the CTIS.
9 years ago when I purchased my 2003 A1 the CTIS controller was bad, purchased a new one and never had another problem with the controller. Never having wiring problems but many different electrical components have failed.

It’s pretty common apparently to get water intrusion in the 10 pin connector area of the CTIS harness and PCU, as well as grounding problems up at the dash and where the controller bolts to the panel. That little ground wire that is supposed to be clamped under the controller is actually the reference ground for the system and I am not sure what havok that causes when it’s not making clean contact with ground. When you re-tightened down your new controller you may have inadvertently improved the grounding.

Did you try your old one in anyone else’s truck? To be clear I’m not saying these can’t possibly ever fail. Maybe yours did. But for example: I was fiddling with one that had “Broken” and a huge white X written on it in grease pen. It had SIX separate stored codes for solenoid faults, PCU transducer errors, inflate trend, etc. I’m guessing in that truck the wiring to the PCU was screwed up or something but on the bench I cleared out all the codes and the thing worked perfect, solenoids snapping fine and the transducer read atmospheric pressure just fine.

 

[Keith Knight]

Good information thank you

 

[Ronmar]

Any of the “bad" units that you have tested good have 5 solid lights?

 

[Lostchain]

Any of the “bad" units that you have tested good have 5 solid lights?

I have not run across one of those yet. I haven’t made it through my pile though so we will see. That’s the only code (from my reading) that Dana documentation points to a faulty controller. @GeneralDisorder has a compelling theory that when you change the config pins to over write the internal memory, it may bring a 5 solid code back to life. It appears you can tell the memory is being overwritten by the first time the config pins are changed, the run flat light goes solid for a bit before it drops into blinking highway. Subsequent powerons start immediately in highway mode. I have had multiple units behave this way, so it’s possible the reconfig of the unit due to my bench harness is clearing out the config memory and allowing the controllers to boot.

I would love to get ahold of a known 5 solid light unit to test this theory.

 

[Keith Knight]

This is a great thread! Just saying….

 

[aw113sgte]

Not much to add, but I got 2 black controllers on eBay that were thrown away, no warranty, like $35 each. Both function perfectly fine. Sample size of 2.

 

[Ronmar]

I have not run across one of those yet. I haven’t made it through my pile though so we will see. That’s the only code (from my reading) that Dana documentation points to a faulty controller. @GeneralDisorder has a compelling theory that when you change the config pins to over write the internal memory, it may bring a 5 solid code back to life. It appears you can tell the memory is being overwritten by the first time the config pins are changed, the run flat light goes solid for a bit before it drops into blinking highway. Subsequent powerons start immediately in highway mode. I have had multiple units behave this way, so it’s possible the reconfig of the unit due to my bench harness is clearing out the config memory and allowing the controllers to boot.

I would love to get ahold of a known 5 solid light unit to test this theory.

And that has been a fairly frequent question over the past few years, both here and in other groups since I joined this club. “My CTIS has 5 solid lights”, mine included… That failure alone in what is a relatively small community puts CTIS into the high failure category IMO, not to mention all the other fault scenarios including system wiring, I have helped troubleshoot…

 

[GeneralDisorder]

And that has been a fairly frequent question over the past few years, both here and in other groups since I joined this club. “My CTIS has 5 solid lights”, mine included… That failure alone in what is a relatively small community puts CTIS into the high failure category IMO, not to mention all the other fault scenarios including system wiring, I have helped troubleshoot…

Wouldn't it be convenient if (some of) those unit just needed an option pin change that forces a reload of the option pin information from ROM to get them working again? I suppose that Dana and the Army don't want to mess with that at the unit level and it may indicate more than corrupt data in some cases - could be an indication of bad volatile memory being used to hold the current program. Could be a transient problem, something related to under/over voltage, etc. There's no good way to have soldiers attempt to have it load a different option file without several pitfalls - possibly the controller failing again at a later time, and at the very least it would make it well-known at the Motorpool level that these units can have their settings changed which is not the purpose of the system - the purpose is so the military can control the tire pressures at a global, Army-wide level and the soldier only needs to press a button. Having the tools and knowledge to perform this procedure would not be conducive to the over-riding goals of the system.

 

[Ronmar]

Wouldn't it be convenient if (some of) those unit just needed an option pin change that forces a reload of the option pin information from ROM to get them working again? I suppose that Dana and the Army don't want to mess with that at the unit level and it may indicate more than corrupt data in some cases - could be an indication of bad volatile memory being used to hold the current program. Could be a transient problem, something related to under/over voltage, etc. There's no good way to have soldiers attempt to have it load a different option file without several pitfalls - possibly the controller failing again at a later time, and at the very least it would make it well-known at the Motorpool level that these units can have their settings changed which is not the purpose of the system - the purpose is so the military can control the tire pressures at a global, Army-wide level and the soldier only needs to press a button. Having the tools and knowledge to perform this procedure would not be conducive to the over-riding goals of the system.

Yep, would be very interesting, but considering the 5 solid = fatal fault coming from the manufacturer does not indicate this is possible… but they are in the business of selling modules

 

[KN6KXR]

Nice to see somebody do this on a bench. I made a "breakout harness" for my M936A2 that uses the same STE ICE components but on the truck. So I test and program on the vehicle.

It's different for the FMTV I have to make another breakout harness. The pins are in different locations. I bought the connectors just need bench time to solder it all up.....

So far the only controller I've found dead wouldn't light up at all. One day it just died. Checked the power supply all good, put another controller on and it worked, called it done. I think a lot of controllers are condemned by mistake. They are pretty robust devices especially the later ones that are fully potted.

 

[olly hondro]

Yeah, I swapped out a controller because it would not allow for deflation. Turned out the vent port on the frame was completely plugged with dead insects.

Insects blocking brake vent lines?

I had read about that here somewhere, and I thought that was pretty silly. Well, now not so much :)

www.steelsoldiers.com

 

[Primussucks]

I haven’t got too far into my CTIS yet. But my controller just doesn’t have any lights at all.

Considering my wheels don’t have any valves on them right now. And no plugs. It’s not a huge priority.
I’ll be doing eco hubs, CTIS seals, and inner bearing seals in the coming weeks. Also got some valves from Callmecolt.

So controller will quickly follow.

I did check the fuse and everything looked fine there, but haven’t looked beyond that.

Will be watching this thread. Thanks for the info.

 

[Lostchain]

I haven’t got too far into my CTIS yet. But my controller just doesn’t have any lights at all.

Considering my wheels don’t have any valves on them right now. And no plugs. It’s not a huge priority.
I’ll be doing eco hubs, CTIS seals, and inner bearing seals in the coming weeks. Also got some valves from Callmecolt.

So controller will quickly follow.

I did check the fuse and everything looked fine there, but haven’t looked beyond that.

Will be watching this thread. Thanks for the info.

So what I learned building my harness is that if you don’t have power going into the blackout pin, the display will stay off. So you should check for +24 at pins “S” (blackout) & “H” (ignition switched power) and then a good ground at “F” and “P”(reference ground). Check for these at the truck side of the connector.

 

[Ronmar]

Yep, the display does blackout i seem to recall helping with a problem like this…

 

[Primussucks]

So what I learned building my harness is that if you don’t have power going into the blackout pin, the display will stay off. So you should check for +24 at pins “S” (blackout) & “H” (ignition switched power) and then a good ground at “F” and “P”(reference ground). Check for these at the truck side of the connector.

great! thanks Lostchain.
I know something is working, since i can hear the manifold 'burp' under the PDP when i turn the truck off...
I hope to get the hubs swapped in the next few weeks and will use this post in my troubleshooting.

 

[Primussucks]

Yep, the display does blackout i seem to recall helping with a problem like this…

Ron..
I know you've posted it before, and I see it in your youtube video.. Do you have the pic handy with the pin outs labeled? Search is eluding me.

 

[KN6KXR]

Looks like there's one hosted here: http://manuals.chudov.com/M939-Series-Trucks/CTIS-AXTS-0015.pdf

The FMTV is the "flange mount wiring diagram" page 66.

 

[GeneralDisorder]

great! thanks Lostchain.
I know something is working, since i can hear the manifold 'burp' under the PDP when i turn the truck off...
I hope to get the hubs swapped in the next few weeks and will use this post in my troubleshooting.

What you are hearing under the PDP when you shut off the truck is the fan solenoid de-energizing and dumping the air from the pneumatic line that disengages the fan clutch. The CTIS you will hear after you power on the truck assuming there is enough air in the wet tank to open the brake protection valve and close the CTIS pressure switch. Usually - for most trucks this is after a short idle time to get the wet tank up to pressure but occasionally you run across a truck that doesn't bleed down overnight and will check tire pressure immediately. The CTIS controller checks tire pressure every 15 minutes by default.