M931A2 CTIS stopped working

[ichudov]

I have a M931A2 semi tractor.

It used to have a functional CTIS, it would deflate the wheels and inflate them. I tested it a couple of months ago.

Now (1 month later) it is not working. The symptom is as follows:

1) I start the truck
2) A few seconds later, farts are heard as the CTIS performs start-up operations
3) CTIS starts blinking all lights

Could anyone shed some light on what likely is the culprit, I want to maintain it in a running condition if possible.

The tires seem all to be inflated properly.

 

[doghead]

http://www.google.com/url?sa=t&rct=...=2gn39HCGdJKPlCwV77AiQA&bvm=bv.54934254,d.dmg

 

[HASSON1911]

Mine quit working too, found out on of the hub seals went and filled the valve with oil, made the computer show 5 flashing stars. If you want the cool factor Id start there checking the tire valves. If you had it just as a convenience, do what I did unplug the controller and plug off the tires.

 

[chadande]

I had that happen when I picked up my truck last winter.
Pressing sand and letting it air down right away after flipping on the power fixed it, I assume by equalizing the pressure in all the tires. But your mileage may vary.
Good luck.

 

[ichudov]

I had that happen when I picked up my truck last winter.
Pressing sand and letting it air down right away after flipping on the power fixed it, I assume by equalizing the pressure in all the tires. But your mileage may vary.
Good luck.

Thanks. I have a vague recollection of having done the same thing once. I will try that exact thing again in the morning.

 

[ichudov]

An update. I think that it has not stopped working. I think that CTIS is properly reacting to imbalance of pressure between tires and displaying a warning.

When I started the truck this morning, I saw five lights, then I hit RUN FLAT, SAND, HWY. That got the truck on the right track, it inflated all tires for highway, no more warning blinking lights.

 

[chadande]

Sweet, glad that worked. I like CTIS and use it regularly if for nothing else than I think it's cool.

 

[bulldog_mack13]

I have a new issue , I read the TM doghead posted.

My CTIS was working on the trip home. I had a air problem and the truck wouldn't cut off building air at the correct PSI. I replaced the check valves and rebuilt the air dryer and fixed the issue 100%.

Now when I crank my truck and its running , the CTIS doesn't make the "buzzing" noise on the PCU on the firewall in the cab and it doesn't make the "fart" noise outside the truck when it does its checks and the single HWY light always blinks...

PCU that went bad or what do you think guys?

 

[bulldog_mack13]

Bump?

 

[Suprman]

The governor is on the firewall the pressure protective valve is down between the air dryer and tank area. See if your wipers and horn work. If the ppv does not open then there is no air supply for the ctis. Replace the ppv.

 

[bulldog_mack13]

Everything works as it should but the CTIS light stays blinking HWY and no noises are heard.

 

[bulldog_mack13]

Also , when you drain the air tanks if you drain number one , it drains all the air out of the truck without turning the others?

 

[Suprman]

If the hwy light is flashing and the system is just idling it is probably waiting for the signal that the air tank has 120psi so it can do an initial pressure check. There is a switch on one of the tanks for this. There is also a small catch filter on the air feed to the valve body in the cab. The lower section unscrews you can clean it out.

 

[bulldog_mack13]

Suprman , I fixed the filter your talking about in the cab.

Can you get me a pic or tell me how to find the switch your talking about. I figured there had to something that's not sending a signal to the CTIS.

I replaced everything going from the air dryer itself to the wet tank.

 

[Suprman]

There are 3 switches on the tanks 2 are for the low air warning and one is ctis I dont remember which is which but you can see them when you look in towards the tanks from the passenger side by the air petcocks.

 

[bulldog_mack13]

Ok , I know what your talking about. I will take it off and see if Napa or anyone has one tomorrow. Thanks for helping me!

 

[Suprman]

Napa won't have one. Make sure both tanks go up to 120psi. You can jump the wires that go to the switch with a wire and see if the system does a pressure check. It could just be a bad contact. Some of the switches are actually rebuildable. I have seen controllers go bad also.

 

[bulldog_mack13]

I checked the switch that has the two wires near the air drains. The truck builds 120. The PCU in the picture doesn't make a noise. I know the power cord that goes to the left side top of the PCU is unhooked I did it to move it around. When its unhooked all 5 lights flash , hook it up it goes back to 1.

 

[Suprman]

Did you find the correct switch and verify that it closes at around 120psi. The other 2 switches close around 60psi they don't affect the ctis. You can unscrew the ctis air feed filter and start the truck to see if you have a good air feed with no blockages. If the pressure switch is working properly and you have a good air feed, all of the electrical connectors are connected and the hwy light is flashing on the controller then it could be a bad controller.

 

[bulldog_mack13]

Can you put up a picture or tell me more about the 120 switch , its not the one that's under the exhaust elbow with two wires coming from the top?

I do have good air feed from the yellow line , electric is connected. If you can tell me more about the 120psi switch in case I checked the wrong one.

Id hate to think I have a bad push button controller for the CTIS that went bad out of no where. , Jay