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If the gages are correct, 95 psi is not enough to activate the ctis initial self check.
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New M1089 FMTV owner
- Thread starter 319cssb
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I'll check the pressure at the air tank today. The last tank has an air fitting on it, I bet it never gets drained properly . I'll then bypass the pressure valve and see if that kicks the CTIS on. But I have suspicions since I don't even have to start the truck for the fault to show up.
wandering neurons
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WARNING - If you haven't been warned before, make sure that the truck master power switch is off when you are plugging/unplugging the ECU. Bad things can happen...
I managed to find a complete PCU on <large online auction site> in the Collectibles/LMTV or FMTV. Swapped entire upper half, including the PCU and solenoids. I tested the solenoids first to make sure none were opened/shorted.
My guess is that as soon as the ECU is powered, it does a POST (power-on self test) that includes the PCU, including ambient pressure from the PCU transducer. If the transducer is out of spec, then it fails to five flashing without even checking for ~120 psi at the wet tank.
I think that there were numbers on the transducer that came with my new PCU. I'll take apart my dash today and see if I can find and post them.
Just my $0.02
I managed to find a complete PCU on <large online auction site> in the Collectibles/LMTV or FMTV. Swapped entire upper half, including the PCU and solenoids. I tested the solenoids first to make sure none were opened/shorted.
My guess is that as soon as the ECU is powered, it does a POST (power-on self test) that includes the PCU, including ambient pressure from the PCU transducer. If the transducer is out of spec, then it fails to five flashing without even checking for ~120 psi at the wet tank.
I think that there were numbers on the transducer that came with my new PCU. I'll take apart my dash today and see if I can find and post them.
Just my $0.02
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It may not be recommended or condoned, but I took off several hoses from the PCU behind the passenger kick panel and sprayed some silicone lube into the unit. I felt that moisture had made its way in there and corroded things a bit. It seemed to help the solonoids on that unit cycle better for pressure checks and changes. FWIW. YMMV.
I was thinking of doing something like that myself. definitely something I am going to try now. thx TN
I took off various connectors and played Silicone spray in them. Also some down the hoses as much as I could. I noticed the connector on the lower right side had the color tight bot the rear end of the plug was able to twist. Not sure if that is supposed to be that way, But that could be an issue.
Connected the Miltope to the truck and I am getting some live data. So the next step is to download the CTIS file , that Suprman talked about (if I can find them )
Connected the Miltope to the truck and I am getting some live data. So the next step is to download the CTIS file , that Suprman talked about (if I can find them )
I actually made a mistake it's 100psi not 95psi
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Still not enough pressure.
So if i understand it correctly then every time I would have empty air tanks and turn on the truck it would show an error? because there isn't enough pressure?
I have downloaded this DDT and it keeps saying that the ECU is not responding. Updated the driver and it still is doing the same
I think the CTIS module might be at fault.
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The system won’t start till around 115 psi. Shouldn’t error for a certain time period from initial start. It knows to give time for the pressure to come up. You should still be able to communicate with it. Could be a bad ecu.
Bad ECU that's what I'm thinking
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Borrow one somewhere see if it works.
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He can connect to the engine. Same data bus on the c7 trucks.
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You want to see around 125 at governed pressure. As the air is building, once you reach governed pressure, the governor sends an air signal to the unloader valve on the compressor to stop making pressure and also to the air dryer to purge built up moisture out the bottom expello valve. The governor is on the air compressor there is a plastic cap under which is a slotted end threaded rod with a set nut, used to adjust the pressure set. May only take a 1/4 turn to adjust. A clogged up air dryer will cause low pressure also but you may not get the purge from the expello valve since you arent actually reaching the governors pressure setting if this is the case.
I'll get a new purge valve tomorrow. It keeps blowing without getting the proper pressure. Once I got the new valve in I'll see what kind of pressure I get then. And then maybe see what the governor adjustment would do.
I think the CTIS has a separate issue, since my DDT won't even connect to the ECU.
Thank you for your help Suprman
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?
so what if the governor is bad? does someone have a replacement?
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Over the counter part. Service the air dryer. May be compressor unloader needs a rebuild.