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So thanks to all of your help, some troubleshoot and most importantly thanks to NV555, the CTIS came back to life. just as we assumed already, it was the pressure sensor, which is mounted at the valve block. update: with the CTIS working, the air dryer purges a lot more. Maybe that will take...

I do get a signal spray when the system reaches pressure. If the truck never had the tanks drained , then there could be a lot of water in the system. A sham shields mission is to do the least amount of work possible. Ask me how I know.

I have a gazillion things I need to go through, still. And If the air dryer filter doesn't need to be one of the things I have to spend money on right now, I'd prefer not to. Still got to change all fluids, filters. get the transmission fluid changed to OEM Allison recommended fluid and so on...

How do find out whether I need to change it?

I have a 2006 M1089A1, they only come with one style of airdryer in those years . The finned type was a thing of the 90's, if I'm not mistaken. i was asking about a) how to drain it ( think by using a 5/16 square drive) b) how to make sure it's not clogged then I can still decide whether I...

Do I understand it correctly, that to drain the air dryer and 'make sure it's not clogged' involves a 5/16 square drive? I don't know how else to make sure it's not clogged

that's correct, But it also has a shut off. If there is no pressure it won't even switch any resistance. Therefore, unless system pressure is building it won't even turn the CTIS on. Once the ECU senses a change it monitors the values. or throws an error code.

The variable pressure sender.

If I'm correct, I think on a working sensor there should be continuity between pin B and A should out of range on an empty tank. And on pressure there should be a resistance.

i think the issue might be the solenoid block itself. anyone got one for sale? i took off the exhaust hose and there is a faint amount of air coming out. the solenoid clicks, but there isn't much air coming through

Actually I got the slightly low voltage on the pressure switch by the tank. At the pressure sensor by the valve block I got over 5V , which is normal according to the troubleshooting guide. I do have a working diagnostic tool. But nothing to respond to it. The ECU pin J to Pressure transducer...

Well, I was able to establish a couple of things: -the air pressure goes up to 120PSI -the air dryer purges moisture from the center as it should. -wḣen I dump the air there is a bunch of moisture and then Ice flying from the purge valves. -the solenoid block likely doesn't have a stuck valve (i...

I have to apologize. apparently I was lying , what I've been messing with was the pressure sender of the wet tank and not the pressure transducer. That one is found on the valve body on the passenger side.

So if I understand the principle of operation of this transducer correctly it should be open in ambient air and closed under pressure, correct? I sprayed it with some stuffs and let it sit upside down for a while and then reinstall and see what happens.

All the pins on the cannon plug check out b, c and r to ground = ~60ohm all cross connections b to c, b to r and c to r =~ 120 ohm taht leaves a bad pcu pressure transducer? How do I check for that again? im getting 4.75V at the transducer plug.

That's exactly what mine does. two flashes then all 5. whether there is air in the tank or not. or full pressure. Same thing with the other good ECU. I'll grab my fluke 87 tomorrow and do some checking. thx wandering neurons

I posted earlier that the connector on the manifold has a tightened collar but the rear part of the plug is loosely moving left and right. That didn't seem to be normal to me. I think the entire plug should be solid when it's tightened on the plug

That's what I've done replaced with a known good one. I've bypassed the pressure switch before with no result will try again

What kills me is that even with 120psi. The CTIS goes right into fault. And still does not respond to DDT

So I got the new valve in the pressure still seems to stay at 100psi I turned the governor counter clockwise about a 1/4 turn. No change. I got a new CTIS module, which also goes into fault mode. so what if the governor is bad? does someone have a replacement?