M939 CTIS Controller for my FMTV?

[Kevin Means]

Hi again everyone. When we bought our M1083, the CTIS controller's lights were all steady red when powered up, which I've learned means it is pretty much useless. While searching for a replacement, I came across an identical-looking Spicer controller, but it says it is for an M939 rig. I watched a YouTube video of a guy who installed one in his LMTV and he said it works fine - albeit with slightly higher tire pressure settings. Is there any reason such a controller would NOT work in our M1083? Thanks

Kevin

 

[GeneralDisorder]

Don't do that without careful research and understanding of the wiring differences. The YouTuber you saw may have just got lucky because most of the older truck CTIS controllers like the 900 series have undocumented voltages on CANBUS pins and they often cause the J1939 resistors to literally burst into flames if you put one in an FMTV. That guy may already have burnt out his coms resistors and doesn't know or understand what he did. Follow youtube videos at your and your trucks peril. The CTIS system is very mis-understood and often deleted or disfigured due to this lack of understanding. He also might have an A0 truck and those trucks don't have communication busses so they won't be damaged by a 900 series controller (but it would damage the diagnostic Y-harness if you tried to use it for coms with the controller). But that is not the case for an A1+ truck. And in any case the pressure settings and overspeeds are different/wrong.

Also the various modules have different settings programs and some are not going to give you the expected results because they come from a different vehicle series and their pre-programmed settings that are chosen by the chassis wiring harness you plug them into may be radically wrong for your use case which would require a DPA and the software to change the settings. But those settings changes will only be temporary if the module goes into a different harness configuration it will revert to standard programming. You can't go off what someone says the settings are because they can be (temporarily) changed and the controller contains 9 different programs that are chosen by each specific vehicle's wiring as determined by the Army. Thus moving compatible controllers between trucks will NOT result in the pressure settings from a differently configured truck being erroneously applied to the wrong truck configuration and causing an accident.

 

[Ronmar]

Yep, may or may not work… can replace the whole thing with 3 switches and a pressure gauge for simple manual control…

 

[KN6KXR]

OK first read through this: http://manuals.chudov.com/M939-Series-Trucks/CTIS-AXTS-0015.pdf

The pinout looks like it will work but as stated above the data pins are in different spots. I would not plug one into an FMTV/LMTV unless I disconnected the data buss on the vehicle from the controller. I would not hesitate to plug an FMTV controller into a M939 series as they were never wired in for it.

I know this because I have an M936A2 and an M1087A0 and have made adapter harnesses with data breakouts for both of them. They are a PITA to make I was disappointed the M939 CTIS harness would not work with the M1087 harness and had to make another. At any rate once you do this you can plug a Dearborn adapter and a laptop into it and reprogram them using the Dana software. I'm happy with the result except that I can't get the software to go over 80psi (for the 939) it keeps asking me for a factory challenge code and Spicer is no help.... otherwise nice to be able to do that.

As for the 5 lights.... I think there's a lot of misinformation out there about this. The only time the controller is toast I've found is when there are no lights at all. Everything else I found was another part of the system failing something. I've had bad PCU's, bad wheel valves, bad hub seals, etc. etc.. The only dead controller I experienced had no lights at all.

 

[Ronmar]

Well mine had 5 solid lights on when I got the truck. Every other part of the system was fine, including the pressure sensor and switch, but that unit was an absolute dead fish,,no function at any time under any condition…

 

[GeneralDisorder]

I have seen multiple 5 solid light failures that were completely unrecoverable. So has @Lostchain who put together a full bench test station for the CTIS controllers using a new old stock FMTV harness. It is absolutely a thing. Not even changing the chassis wiring to use a different program will work. They are just dead. My guess is corrupted EPROM's. While the power supply may function, the boot-up sequence is not completing. At least that's my guess.

 

[MatthewWBailey]

Yep, may or may not work… can replace the whole thing with 3 switches and a pressure gauge for simple manual control…

But everyone likes bells and whistles!. I'm still gouging out a scrap CTIS controller box to salvage the connector so I can do your relay setup.

 

[Ronmar]

I’m getting too old for bells and whistles… I just want crap to work when I flip the switch