LMTV CTIS Question

[Stellaevil]

I've been running my CTIS in manual mode for over a year and would never go back to the computer setup. I did this primarily for reliability in the field, and flexibility in what pressures I can select.
Be careful with using too small a fitting as it will limit your fill times. I probably could have used smaller valves, but my setup works great and I am quite happy with the result.

It is good that you have a vent valve to dump the pressure to atmosphere so you are not running the air seals continually pressurized. How does this setup handle a deflation?

 

[Pointman0853]

Works perfectly, airs up , airs down. Very happy with the computer-less setup. Infinite pressure variations and works every time!

Pointman

 

[wandering neurons]

Welp, I did as SuprMan suggested and turned up the compressor governor 1/4 turn. Per the 20-3 TM, counterclockwise from the front of the motor increases pressure. That didn't do a thing. I finally paid attention (too poor to normally pay attention) and realized that my CTIS ECU fails when I power on the truck. Turn on the master switch, get 1-2 HWY flashes then goes all five flashing. Unless I've got a bad ECU or someone has some other thoughts, it's time to go all manual CTIS. Sad, because I paid good money for the ECU, PDU solenoids and valves. Sigh. FMTV FML.

 

[Stellaevil]

Welp, I did as SuprMan suggested and turned up the compressor governor 1/4 turn. Per the 20-3 TM, counterclockwise from the front of the motor increases pressure. That didn't do a thing. I finally paid attention (too poor to normally pay attention) and realized that my CTIS ECU fails when I power on the truck. Turn on the master switch, get 1-2 HWY flashes then goes all five flashing. Unless I've got a bad ECU or someone has some other thoughts, it's time to go all manual CTIS. Sad, because I paid good money for the ECU, PDU solenoids and valves. Sigh. FMTV FML.

The ECU is fine it doesn't like something from the pressure transducer. Follow the procedure in the guide.

https://www.steelsoldiers.com/showthread.php?175911-Central-Tire-Inflation-System-(CTIS)-AXTS-0015-2018

 

[wandering neurons]

Welp, I may have a fully functional CTIS! That is, pending fixing my two right rear air chambers so I can pressurize the air system on the truck.
I re-checked wiring and it checked good. Then I found a PCU on flea-bay, in the Memorabilia section! Looked pretty good other than a cracked fitting for the pressure relief fitting. It arrived today and I tore it apart. It was dated '07, whereas mine is a '97 model. Identical otherwise. I used my old lower half of the PCU and transplanted the upper half, with the solenoids and associated stems, and the pressure transducer. All solenoids measure 60 ohms, so good there. I used my old lower half as I've replaced all the moving parts and new seals between the halves. And it's cleaner than the newer one in that section.
Anyway, replaced everything, applied power (but did not start) and the HWY light just sits and flashes, waiting on air pressure. Not flash HWY 1-2 times then all five flashing forever after.
I'd guess that the pressure transducer had failed, causing the ECU to trigger five-flashing. Didn't matter if I pressured my truck from the engine compressor, or used shop air to pressurize via the front emergency glad hand. The flashing failure started immediately after power-on, regardless of air system pressure (0 oro 125 psi).
Will follow-up if anything changes, but log that in the CTIS WIN category for now!

 

[wandering neurons]

Update - did a temp fix to the brakes, fired up the truck. HWY light flashed for a few minutes, heard air at the tires for a few, then burst of pressure, hissing stopped, HWY light stopped flashing. Success!

Sort of - selected SAND mode, SAND started flashing. Got more air hissing, then after a few minutes, got flashing HWY and XC. Selected HWY, got flashing HWY, then after a few minutes, hissing stopped and HWY stopped flashing. I think I've got an air leak under the truck associated with the CTIS, but I'll have to crawl underneath and find it. But a 100% improvement!

Conclusion: The pressure transducer in the PCU was faulty. That tripped the ECU before the CTIS got air pressure, and before anything happens with the solenoids.

 

[Stellaevil]

Update - did a temp fix to the brakes, fired up the truck. HWY light flashed for a few minutes, heard air at the tires for a few, then burst of pressure, hissing stopped, HWY light stopped flashing. Success!

Sort of - selected SAND mode, SAND started flashing. Got more air hissing, then after a few minutes, got flashing HWY and XC. Selected HWY, got flashing HWY, then after a few minutes, hissing stopped and HWY stopped flashing. I think I've got an air leak under the truck associated with the CTIS, but I'll have to crawl underneath and find it. But a 100% improvement!
Conclusion: The pressure transducer in the PCU was faulty. That tripped the ECU before the CTIS got air pressure, and before anything happens with the solenoids.

You are correct about the leak, there should be no audible air during an inflate. Two flashing lights means the system is stuck between two modes and is not inflating fast enough. I like to use shop air plumbed to the wet tank to check for leaks. if you don't have >115psi to close the pressure switch you can short the harness connector with a paper clip. You just need +10psi above the tires to test properly.

 

[lrholding]

Finally got back to CTIS issue. Suprman i believe hit the nail on the head. I connected air supply to wet tank and repeatedly started the system searching for leaks. Suspected front left wheel hub was leaking. Capped supply line to wheel and system worked properly, steady terrain light (hwy), no more flashing of hwy and run flat!

Anyone know where to get required hub seal and other required parts?

LRHOLDING

 

[NV555]

I do not trust the CTIS system. My is working as it should however I just leave it unplugged unless I need to change the tire pressure.

If anyone is in a bind I have an extra working controller.

 

[Ohiobenz]

I get the simplicity of going manual, but the automatic check every 15 mins has it's own value.
It sounds like just disassembling everything and making sure there are no leaks, including the PSU, is the most logical way to start. Otherwise it sounds like just chasing your tail....
Has anyone done a flowchart of the CTIS functions?

 

[lrholding]

The latest version (2018, 017) of the Dana/Spicer troubleshooting guide seems to have the most detail of the system function.

Soapy water spray bottle, shop air supplying the wet tank and a very quite area to listen for leaks worked for me.

LRHolding

 

[Ohiobenz]

The latest version (2018, 017) of the Dana/Spicer troubleshooting guide seems to have the most detail of the system function.

Soapy water spray bottle, shop air supplying the wet tank and a very quite area to listen for leaks worked for me.

LRHolding

Been reading the trouble shooting guide, good stuff. Right now Im still in the beginning stages of ownership. The plan is to work from the wheels forward and just rebuild everything....

 

[wandering neurons]

OK, not 100% operational as hoped. From HWY, if I select XC or SAND, get about 30-40 seconds of pressure coming heavily from both QRVs underneath (verified by crawling underneath and checking both). After the 30-40 seconds, HWY and XC lights come on steady. Press XC or SAND again, another 30-40 seconds. Press HWY and tires re-inflate normally. I can't find or hear any leaks from valves or seals. I tried unscrewing the screw on the CTIS wheel valve three turns per -20-2 CTIS troubleshooting. Nothing happened. I did not pull the screw completely out though.
I'm thinking either bad wheel valves or the filters therein. I was also thinking that there could be valve cores in the stems in the wheels, but if I press the core on the wheel valve I get air coming out.

Beuller?

Update - did a temp fix to the brakes, fired up the truck. HWY light flashed for a few minutes, heard air at the tires for a few, then burst of pressure, hissing stopped, HWY light stopped flashing. Success!

Sort of - selected SAND mode, SAND started flashing. Got more air hissing, then after a few minutes, got flashing HWY and XC. Selected HWY, got flashing HWY, then after a few minutes, hissing stopped and HWY stopped flashing. I think I've got an air leak under the truck associated with the CTIS, but I'll have to crawl underneath and find it. But a 100% improvement!

Conclusion: The pressure transducer in the PCU was faulty. That tripped the ECU before the CTIS got air pressure, and before anything happens with the solenoids.

 

[Stellaevil]

OK, not 100% operational as hoped. From HWY, if I select XC or SAND, get about 30-40 seconds of pressure coming heavily from both QRVs underneath (verified by crawling underneath and checking both). After the 30-40 seconds, HWY and XC lights come on steady. Press XC or SAND again, another 30-40 seconds. Press HWY and tires re-inflate normally. I can't find or hear any leaks from valves or seals. I tried unscrewing the screw on the CTIS wheel valve three turns per -20-2 CTIS troubleshooting. Nothing happened. I did not pull the screw completely out though.
I'm thinking either bad wheel valves or the filters therein. I was also thinking that there could be valve cores in the stems in the wheels, but if I press the core on the wheel valve I get air coming out.
Beuller?

One of two things; check the starting tire pressures and when is stops, if it did not deflate more than 5psi it will log a "between modes" fault (filters). Or, the deflation relief valve on the PCU (brass valve) is out of range stuck or dirty will log a 2 light fault.

 

[wandering neurons]

Well, the brass valve on the PCU has been checked and swapped, so I just ordered a set of filters, though the order may take a few days. I'm going to double-check the wheel valves, I may have tested them while the CTIS was pressuring the tires. But that's an easy test...

Thanks for the info, will post when I find out the results. I'm > < this close to having this working...

One of two things; check the starting tire pressures and when is stops, if it did not deflate more than 5psi it will log a "between modes" fault (filters). Or, the deflation relief valve on the PCU (brass valve) is out of range stuck or dirty will log a 2 light fault.

 

[spankybear]

So if I am reading this thread right all lights on steady is a bad ECU? It was working fine but I had removed the ECU to get the panel behind off. Putting everything back together and when I powered up all lights where flashing... when I started it up yesterday all lights where on steady. What did i do?

 

[Coffey1]

You didn't unhook it and rehook it with power on.
That can fry it's tiny little brain.

 

[spankybear]

You didn't unhook it and rehook it with power on.
That can fry it's tiny little brain.

No and the batteries where disconnected...

 

[Stellaevil]

You didn't unhook it and rehook it with power on.
That can fry it's tiny little brain.

Never Happen!
The connector key is pretty reliable and the circuit is tested for reverse voltage and large power spikes. They simply get old and the capacitors in the power supply start to leak.

 

[spankybear]

Never Happen!
The connector key is pretty reliable and the circuit is tested for reverse voltage and large power spikes. They simply get old and the capacitors in the power supply start to leak.

Are they potted or can you service the unit?