CTIS troubleshooting

[ckouba]

Trying to troubleshoot my CTIS. Anyone seen something like this before?

I went for a drive and it was working fine. Stopped for a bit and when I restarted it, this happened. Solenoids keep cycling and when there's enough air you can hear the discharge.

Both Brandon and Rick have helped troubleshoot a bit, but we haven't been able to fix it.

Symptoms persist after controller swaps and PCU rebuild. If I unplug the controller, all is good.

Pressure regulator seems to be set correctly.

Any ideas?

 

[Ronmar]

That looks like a weak or high resistance electrical/ground connection to the coils of the PCU solenoids.

A bad connection will pass full voltage, untill you pull current thru it. On a relay or solenoid coil it sees full voltage, and starts to build a field to pull in the contacts or plug. Voltage drops, field collases, contacts releas, coil feeds back voltage, voltage peaks and the cycle repeats.

Pull the connector at the controller, turn on the main switch then jumper between H and R. You should hear only one click as the control solenoid pulls in. Remove the jumper and you should hear one click as it releases.

Repeat the test with jumper between H and B. This is the supply solenoid and you again should only hear one click when you apply or remove the jumper. You may hear airflow if the wet tank is above 85 PSI.

Same test jumper H to C(deflate solenoid). One click only Vasilli...

If you hear multiple clicking you have a bad circuit.

This is how I manually control. Install a jumper H-R and leave it there to hold the control valve closed, then momentarilly jump H to B to give a shot of air to pressurize the system. When done pull the H-R jumper to vent the system or shutoff the ign sw.

This is a great way to look.for leaks engine off as you can hold the system at presure indefinitely if your leaks are not too bad. Any leak will start venting tire air to match the leak.

 

[ckouba]

"One click only Vasilli..."

HA! Someone else who digs up obscure references!!!

But seriously, thanks for the pointer Ron. Will head out to give it a shot shortly.

Chris

 

[ckouba]

Hi Ron,

Just PM'd you.

 

[GeneralDisorder]

The controller keeps throwing codes for the solenoid circuits - mostly the control solenoid but sometimes also the deflate and inflate solenoids.

The pressure switch signal wire has 300 ohms of resistance to chassis ground even when unplugged on both ends.

Did you check the wiring harness where the pressure switch wiring diverges from the C/D/I solenoid wiring?

My guess is there is some harness damage that's involving both the pressure switch wiring and the solenoid wiring - since the system did work when he got the truck I am guessing this damage is a single fault that's causing all the problems.

The controller is telling us there's a wiring issue to the solenoids and since there's not a fully open circuit on the pressure switch wiring it's trying to activate the PCU control solenoid to check pressure before the pressure switch actually closes and tells the controller it's ok to perform the check.....

We have tried my controller in his truck and the symptoms are the same. His PCU is rebuilt and we also tried a second one. So it's neither the controller nor the PCU and that pretty much leaves a wiring fault. We have also checked that all the vent ports are clear and the air lines are connected correctly, etc.

 

[ckouba]

Is there an easy way to break down these connectors? Trying to check for continuity or cross-talk.

 

[Ronmar]

That black cover should slide back to expose where the wires are soldered into the pin cups.

 

[GeneralDisorder]

That black cover should slide back to expose where the wires are soldered into the pin cups.

Should. But they glued it. They are hard to remove in the best case with a 1/3 that number of wires. These are not coming out non-destructively.

 

[Ronmar]

Should. But they glued it. They are hard to remove in the best case with a 1/3 that number of wires. These are not coming out non-destructively.

Yep, they can be a pita. Glued! Morons…

He did the manual jumper method I described above and when he went H-B the jumper got hot in his hand, so something is pulling excessive current somewhere. When we last spoke he was working on looking for cross wiring between the solenoid wires To some other circuit.

i only see one intermediary connector on the harness(circled in red) but not on the solenoid or PCU pressure sensor circuits. They should run from controller connector to solenoid connector on the PCU. Identifying the short is one thing, finding where the actual fault is located, is something else

 

[ckouba]

No smoking gun in checking the cross-talk between wires to the PCU. All ohm out as independent. After picking brains and burning up my own all day, I am very inclined to wire up a parallel manual system like Ron has pioneered. It's looking extremely attractive right now.

My motivation to pull the dash apart to maybe find something is marginal.

 

[Keith Knight]

My CTIS has been working great for the past 7 years. I’ve been on the road full time in it and using it regularly. I’ve installed a switch on the CTIS harness so I can turn it on or off. I typically turn it on first thing before driving to get all the tires to 85 cold psi just in case any slow leak in the tires, then I shut the CTIS off. A few days ago when the system reached 120 psi I turned on the CTIS and the highway light started blinking like normal then I could hear the normal sounds from the passenger kick panel area and half way through the normal sounds it stopped and all 5 lights started flashing. Repeated this multiple times no change. I then read that is an indication of a large air leak so I removed the output air line port C on the valve body then ran pressurized air to the line with a regulator air a gauge. It held 85 psi for 20 minutes as I listened for air leaks. No leaks found holding pressure. When I removed the pressure from the line one of the dump valves opened up. Reconnect the output air line to port C turned the truck back on got the system back up to 120 psi, turtle CTIS on and now I have Highway and run flat starts flashing, then the first 4 lights start flashing. Turn it off the on 5 lights. Each time I turn it off and on I’m getting different lights flashing. Any suggestions?

Also the test procedure Ron described earlier is would that be a good test for this situation?

 

[Ronmar]

My CTIS has been working great for the past 7 years. I’ve been on the road full time in it and using it regularly. I’ve installed a switch on the CTIS harness so I can turn it on or off. I typically turn it on first thing before driving to get all the tires to 85 cold psi just in case any slow leak in the tires, then I shut the CTIS off. A few days ago when the system reached 120 psi I turned on the CTIS and the highway light started blinking like normal then I could hear the normal sounds from the passenger kick panel area and half way through the normal sounds it stopped and all 5 lights started flashing. Repeated this multiple times no change. I then read that is an indication of a large air leak so I removed the output air line port C on the valve body then ran pressurized air to the line with a regulator air a gauge. It held 85 psi for 20 minutes as I listened for air leaks. No leaks found holding pressure. When I removed the pressure from the line one of the dump valves opened up. Reconnect the output air line to port C turned the truck back on got the system back up to 120 psi, turtle CTIS on and now I have Highway and run flat starts flashing, then the first 4 lights start flashing. Turn it off the on 5 lights. Each time I turn it off and on I’m getting different lights flashing. Any suggestions?

Also the test procedure Ron described earlier is would that be a good test for this situation?

The test I described above would be a good next test.

Disconnecting line C and applying regulated air directly to the system is another great way to look for system leaks. You said you connected a line and regulator. Did you shutoff the air supply after you pressurized the system? If the regulated supply was connected it would probably make up for any leaks…

if you pressurized it then closed a valve to remove the supply source and it held for 20 minutes you are probably OK… The dump valves venting briefly is perfectly normal when you disconnect air from that line. the dumps see their input go to zero and make their output go to zero by briefly dumping output side air out the vent. When the wheel valves go below ~5psi, they close and there is no more air left to vent.

connecting air directly to the PCU output line does not however check the PCU for leaks. With the air tanks full, Using the jumpers like I described above, if you put in a jumper between H and R, to close the control solenoid valve and seal the system, then briefly jumper H to B to deliver a shot of supply air to pressurize the system and open the wheel valves, it should also be able to set like that with the system at tire pressure until you pull the H-R jumper or shut off the main switch.

As soon as I do this I immediately get under the truck to see if there is any air coming out of the dump vents. Any air coming out of the dump vents indicates a leak, because as the leak lowers system pressure, the dumps(remote control pressure regulators) will match the decreasing input/system pressure on their output by venting tire air. This would be my same first check if I were applying air directly to the PCU output line(line c in the drawing). Apply air briefly to pressurize the system then close the valve, then check the dump vents. Putting a balloon or rubber glove over the vent port is a good way to monitor for slow leaks that are too small to see or feel.

since you have already tested the main system plumbing minus PCU, and it held pressure, if you detect dump vent air leakage using the jumpers, it is probably the PCU leaking…

 

[ckouba]

After a bunch of troubleshooting and narrowing down my fault to (probably) a wiring issue back inside the dash, I now have functional CTIS again. Functionality was restored with 3 switches and re-wiring the PCU solenoids to work manually in the manner which Ronmar documented in his video. It's quite simple to make work and based on conversations with him, the ability to adjust to any specific pressure should be pretty useful. In hindsight, I should have done this long ago and based on the minimal effort it took, I am very glad I didn't rip my dash apart to chase the wiring.

So a MASSIVE thank you to both Rick, who spent a several hours investigating the issue at my house, and Ron, for the time he spent putting together and documenting the manual activation system- and also for the hour or two he spent on the phone with me explaining how the system works. Thanks gents!

The thread which does the explaining:

Manual CTIS, electric over pneumatic.

Ok, so my CTIS ECU is a brick with 5 solid lights and if I spend too much more on this project my wife will probably bury me in it:) That being said, I am also a bit of a control freak so I am converting to manual CTIS. I have looked at the valve and regulator method but decided to go about it...

www.steelsoldiers.com

Ron's system which I copied into my truck:

My end goal after I acquire the required components:

Currently I used three switches which I literally had lying around, and because I don't have a pressure gauge yet, I have to manually check at the wheels for what my pressure is running. I can confirm the system does run the pressures up and down as desired, I just need to get a more permanent arrangement installed. I was very happy that my system was mechanically healthy and am more than happy to make it work with a little extra wire and a few switches.

My "system":

 

[GeneralDisorder]

That's absolutely excellent that the system is mechanically solid and any method of control that gets it working to your liking is all that matters.

My remaining concern is that we pretty much know for a FACT that you have wiring harness damage and we don't know where it's located - which brings up the potential for that damage to continue to progress into other wires or even other circuits depending on what it's rubbing on or being pinched by, etc. I recall an incident with a Denali not long ago where a harness bundle was rubbing on a driveshaft and wore through till some tail lights didn't work and then went a bit farther and lit up every dash indicator, and then a bit farther and the alternator stopped charging and then a bit farther and...... till the truck had to be towed. Fortunately there was a service bulletin about this potential issue (flawed design) so tracking it down was rather simple after putting the pieces together.