M939 CTIS Reprogram, Anybody Done It?

[aleigh]

So even though my cab is stuck forward ha ha did not stop me from trying the new CTIS computer I got.

https://www.flickr.com/photos/adventioneering/27703157996/in/dateposted-public/

Flashes the lights when the power is first applied, then zero lights (regardless of headlight light position). So that's a problem for another day, once I get my hydro system worked out and the cab back down. I'm guessing at this point I need to start looking for a new valve controller too, just to eliminate it.

 

[Suprman]

Check the connections at the pneumatic valve in the passenger kick. You may have to clean them
up with an eraser.

 

[aleigh]

Wilco

 

[tennmogger]

So even though my cab is stuck forward ha ha did not stop me from trying the new CTIS computer I got.

https://www.flickr.com/photos/adventioneering/27703157996/in/dateposted-public/

Flashes the lights when the power is first applied, then zero lights (regardless of headlight light position). So that's a problem for another day, once I get my hydro system worked out and the cab back down. I'm guessing at this point I need to start looking for a new valve controller too, just to eliminate it.

Aleigh,

I also bought a replacement controller, NOS, same p/n 12378682, and same mfgr 1MVZ1-673204, as your new one. It behaves exactly like your description: Plug it in, power up truck, and CTIS lights blink once, then nothing.

A local guy with an LMTV let me plug his controller into my truck and his controller worked perfectly, lights and all. My cables and other components have to be ok. Yours might be also. I concluded that there is some incompatibility with the new controller. However, this dead-looking controller actually works to control the tire pressure!

Even with no lights, the system works fine. Obviously there is no blinky light feedback for the driver so we have to listen to the system and interpret if it's working or not.

Using my friends controller and seeing my system work proves to me that the zero-lighting issue must be due to a difference in this controller. Reading that your experience with this p/n controller is the same, supports my belief that this controller has something different than the original. I just can't prove it.

When you get your cab back in place, please try that controller again and post whether it works or not. Thanks!

[edit: I had gone through the troubleshooting on cables, etc, checked plugs/sockets, cleaned and sprayed with Deoxit, with no success]

 

[aleigh]

I am half not surprised I guess. The guy on the auction said it was off an MRAP or whatever so the PSI it's programmed with for the highway is too high, so that's a big clue. He claimed it'd work on a 1078 though. The description is as below, which I include just for the interest of it. Maybe our trucks are not rigged up with the sender wire for the illumination - see other threads where people say they are zero lights until they turn the headlights on. Maybe it's looking for a sense signal you see what I am saying. I've got the keypad headlight switch which I am guessing was a retrofit because I thought the early A0 trucks all came with the older mechanical switches. How about you?

HARD TO FINE NOS/NEW CTIS COMPUTER. OTHERWISE KNOWN AS: (CENTRAL TIRE INFLATION SYSTEM). FITS MANY TYPES OF LMTV FMTV M1078's TYPE MILITARY TRUCKS. WILL NOT WORK ON THE M936 SERIES TRUCKS, THEY ARE 24v. THIS CONTROLLER IS 16 VOLTS. WAS TOLD THESE CONTROLLERS ARE FOR THE MRAP TRUCKS. THE ON-ROAD PRESSURE WILL BE 70 LBS INSTEAD OF 60, OTHERWISE ALL OTHER OFF-ROAD PRESSURES WILL BE THE SAME. WILL WORK FINE ON LMTV & FMTV TRUCKS.

 

[Suprman]

That controller part numbe comes back to BAE cat mrap and fmtv. It should work fine in the lmtv trucks. Did you try and turn your headlights on? Some of the m939 controllers have blackout mode with the lights off.

 

[aleigh]

"Flashes the lights when the power is first applied, then zero lights (regardless of headlight light position)"

 

[aleigh]

Here's my guess, the A1s are wired with some sense line for it and the A0s are missing the line or the 18 year old mechanics flubbed it when retro'ing the switches in. Just like my Allison panel dims when the lights are any position rather than dimming when the panel lights are on. So the controller works fine but is dark. My problem in life is my CTIS is not known good and I was kind of hoping to have a very reliable controller to test with so I could get the fault codes and then o-scope the senders to see what the format was. Eyeroll. I will win eventually.

 

[aleigh]

update: so according to the documentation I have, pin S is the blackout input. It should be at battery voltage for lights, or grounded out for no lights. I haven't checked mine yet, I have other complications, tennmogger maybe you want to look at yours.

 

[99nouns]

I have another thread going it has the ctis 90psi wrecker upgrade info and part numbers of the
newest ecu. The newest model should have interface capability similiar to the lmtv.

Link please

 

[aleigh]

So I got my cab down - another story - and checked pin S. Sure enough, no voltage, regardless of the light switch position. It's not grounded either, it's just nothing. I took the cable apart and it is wired. It vanishes off into the dash to who knows where. I haven't tried jumping 24V into it but I surmise this is the problem - something elsewhere is wrong in the truck, it's not getting the signal line, hence no ECU lights. My old one lit up fine before I took it apart.

 

[aleigh]

Ha so the TMs are "wrong", and the breaker schematic. Or so it seems. They label the relay K52 as "CTIS Overspeed Indication Relay".
Pin S on the CTIS ECU makes its way to the K52 relay. If that relay is closed to 87A which is connected to CB40 - the CTIS breaker - it is hot to 24V. This is the normal position.
If the TB3-51 block energizes from CB66 (blackout markers, etc) then K52 closes to nothing, S goes to nothing, and we're not getting our lights.

So I went out to my truck and discovered I had a relay in K52 but it was missing the 87A pin. ha ha. So I put the right kind in.

Now I have CTIS lights!

 

[therooster2001]

Nice troubleshooting! My old ECU didn't need the service lights on, my new one does. You must have had the old one. So your relay was a four pin, not 5? Think someone just put the wrong type back in?

 

[aleigh]

So on my 1078A0 the relay is normally closed to 87A which means that the CTIS lights get 12V normally just when the truck is on. The headlight position does not matter for that. However when you select blackout lighting it energizes the relay and closes it to 87, which drops pin S, which turns the lights out. It also does other things, like dim the WTEC II to an even dimmer level.

So I get and keep lights as soon as I turn the truck on.

And yeah 5 pin I guess - can't count. I think someone just put the wrong one in. Identical problem with the hazards - now I know why the rear didn't work. And they had put a 12V relay in for the exciter - wow that thing was hot - and put the 24V one you needed for that in a 12V slot. Facepalm.

So now my problem is... no lights come on (other than the words). When I press a button it lights up solid but just goes out when I release it. Truck running, up to pressure. This is better than my old ECU which gave 5 lights though so maybe it was toast after all. Back to the TMs!

 

[ScubaCat]

So, I have not read every post in this thread yet, just the first and last couple pages to get the gist of it... Question, has anyone looked at the CTIS modules from the M35A3 trucks? I like those because they are designed to be more easily mounted out of the way, to me anyway, than the conventional M939A2 style along the shifter.

 

[therooster2001]

OK. So a quick update as I did not do a separate thread. This will be short.

I think I will cheat to get the protocol feed by jacking the ECU from the inside through that pin header. I'll see if it's going to be awful. I did figure out how I am going to display it though. Check this out. Don't get too excited, it's just the TV code, not any CTIS stuff yet. Second half is a capabilities demo. Baby steps.

https://youtu.be/4QWraNRuirw

 

[grendel]

I am in for a new controller with diagnostics. . Happy to fund some of it, by buying three.

 

[therooster2001]

OK, I soldered up the 1708 and 1939 connections to wires. Now I need to figure out which protocol and then see what data it gives. The unknown here is that I used a CTIS controller that I didn't check on the truck. This was the one I took apart before. Let's hope that it still works!

 

[grendel]

I can send several known working ones.

 

[Suprman]

Here is some info about the newer model controller.