CTIS connection question

[Ue413]

My M931a2 has a ctis unit that shows no lights when plugged in, however, as I plug and unplug connector, the lights activate. It's almost like it will stay connected at the half way point, but will not.

I plugged this controller in myM23a2, and same thing. My controler from my M923a2 works fine in M931a2, but not the opposite.

Anyone have this issue? If so, how did you resolve? Thank you.

 

[Coffey1]

If your doing this with power on your risking killing the ecu if it goes to 5 solid lights you killed it.

 

[adamsoffroadperformance]

lol mine only works and lights up if I turn on the headlights.

 

[74M35A2]

Sounds like a cracked solder joint on the back side of the board the connector is attached to. As you are wiggling the pins, it is making and breaking the connection.

I have heard of the "only works when light switch is on" issue. Not sure what that is about, but more than one person has had it behave that way.

 

[adamsoffroadperformance]

I'm guessing it has to be a ground somewhere or something is connected wrong somewhere else in the truck

 

[Ue413]

Not a ground...a different module works fine. It is something in the module.

 

[adamsoffroadperformance]

Sorry I meant my problem

 

[Ue413]

Didn't realize until I opened the box, but nothing is going to fail due to water or vibration on the controller. The box is completely encased in potting....which makes it virtually unbreakable and unfixable.

 

[tennmogger]

Didn't realize until I opened the box, but nothing is going to fail due to water or vibration on the controller. The box is completely encased in potting....which makes it virtually unbreakable and unfixable.

I have a CTIS control box that behaves as you described in first post. There might be a common mismatch between some box versions and truck wiring.

After plugging it in with power off, then turn power on, I get a flash of lights, then all lights go out. Lights do not come back on under any circumstances yet the module works and controls the CTIS. It is fully functional except for lack of any light indicators. I quickly realized the lights are not really necessary. After you listen to the CTIS operate properly for many cycles, you notice when it is 'wrong'. Sounds are better for diagnostics than the stupid lights!

But you have to remember what mode you left it in or reset it at the beginning of the drive.

Where did you get your CTIS box? Was it in the truck when you got it? In my case, I suspect a vehicle compatibility issue because the control box was bought as 'NOS' but may have come from another vehicle. Anyway, it does the job, sorta. (BTW, a second box I bought NOS was DOA.)

 

[Ue413]

Great tip.....mine came with truck, and I just assumed it didn't work. I will give it a shot and report back.

 

[Ue413]

Finally had a chance to check, and it works just as you describe yours did. Thanks for the advice!

 

[tennmogger]

Great, so your CTIS works! The more you use it, the better you will know if it ceases to work. Pay attention to how it sounds when you start the truck, and how it sounds at the 15 minute checks, and soon you won't care that the lights don't work! Some day someone will figure out what the incompatibility is.

Taking the passenger kickplate off to expose the valve box makes it easier to hear.

Bob

 

[Suprman]

The M939A2 pneumatic valve is exposed on the cab floor with a metal cover partially over it. But the system is pretty much identical.