CTIS 5 flashing lights, no air leaks, no mechanical faults.

[RobertoGatos]

I've hit a bit of a wall. Got 5 flashing lights on my CTIS, and after tracking down all the leaks (there were a few) the system still defaults once the system runs its first pressure check, and tries to inflate. What I'm experiencing is the following:

When the system cycles on, the pneumatic controller has a very slight amount of air coming out of it. I can keep this pressure held back with my thumb. When I do this, the system acts normally. No defaults. Keeps trying to "inflate" albeit VERY slowly. If I allow the pneumatic controller to vent to the output line (headed to wheels) it defaults. There appear to be no leaks between the pneumatic controller and wheels. I can inflate, and deflate using a remote air source.

Replaced the ECU, pneumatic controller, and pressure transducer with units known to be good. Once the system tries to cycle, there is again only a very slight amount of air coming though the output line. Nowhere near the volume of air a functional system puts out. The supply line to the pneumatic controller has plenty of high pressure air, and does not seem to be the issue.

Would like to know if there is something in place that can prevent the pneumatic controller from fully opening?

 

[aztec]

iam having same problem tires stay up no faults until first cycle then 5 lts no leaks

 

[Suprman]

If it goes to 5 flashing lights after the initial pressure check, chances are you have an air leak somewhere. Wheel valve o ring, hub seal something like that. It could also be not enough air feed to the valve body. Clean out the catch trap. Turn up the air governor to 135 psi.

 

[Andyrv6av8r]

What I'm experiencing is the following:

When the system cycles on, the pneumatic controller has a very slight amount of air coming out of it. I can keep this pressure held back with my thumb. When I do this, the system acts normally. No defaults. Keeps trying to "inflate" albeit VERY slowly.

Where exactly are you detecting this air venting in the cab? I hear air going through lines when the system checks the pressure and inflates but I never get any air venting inside of the cab.

 

[doghead]

There are a couple of similar thread if you scroll down, maybe one of them can help you.

 

[RobertoGatos]

Verified there are no leaks after the pneumatic controller. aztec, the easy way to do that is by unthreading the output line from the controller and pressurizing with a remote air source. Have a helper spray soapy water.

If that checks out, unscrew the output line on the pneumatic controller. When the unit cycles on, it should put out a huge blast of air. If only a trickle, than maybe we do have the same problem...

If it goes to 5 flashing lights after the initial pressure check, chances are you have an air leak somewhere. Wheel valve o ring, hub seal something like that. It could also be not enough air feed to the valve body. Clean out the catch trap. Turn up the air governor to 135 psi.

Superman, If I have a huge volume of air coming into the pneumatic controller, (as much I would expect to come out) wouldn't that mean the moisture trap is clear? You are talking about the small moisture catch under the dash correct?

 

[RobertoGatos]

Where exactly are you detecting this air venting in the cab? I hear air going through lines when the system checks the pressure and inflates but I never get any air venting inside of the cab.

After unscrewing the output line of the pneumatic controller. There is a MUCH lower volume of air flowing than an operational system.

 

[Suprman]

There is a over pressure valve on the side of the valve body. That can go bad and leak. There are o rings in the valve body that can leak out the side of the valve body. But if you already swapped out the controller and valve body with tested good ones then chances are that's not your issue. The catch trap is a good place to start by cleaning it out and making sure you have a good 130psi air feed.

 

[Andyrv6av8r]

When the system cycles on, the pneumatic controller has a very slight amount of air coming out of it. I can keep this pressure held back with my thumb. When I do this, the system acts normally. No defaults. Keeps trying to "inflate" albeit VERY slowly.

Do you mean after you have taken the output line to the wheels loose? Maybe when the system comes online what you're feeling is the 12 psi the controller is sending to the wheel vales to check pressure?

 

[Suprman]

Fill the tanks shut off the truck turn on power and run have someone in the cab press run flat or hwy and walk around the truck listening for leaks. I just did this today and was able to find a leaking wheel valve on a truck I just got in.

 

[RobertoGatos]

There is a over pressure valve on the side of the valve body. That can go bad and leak. There are o rings in the valve body that can leak out the side of the valve body. But if you already swapped out the controller and valve body with tested good ones then chances are that's not your issue. The catch trap is a good place to start by cleaning it out and making sure you have a good 130psi air feed.

Catch trap clean as a whistle, and yes, swapped controllers, but thats good to know for the future.

 

[RobertoGatos]

Do you mean after you have taken the output line to the wheels loose? Maybe when the system comes online what you're feeling is the 12 psi the controller is sending to the wheel vales to check pressure?

Yes, but the air is coming out so slowly. On my other trucks, there is a much larger burst of air. You can also hear the difference between this truck and others. The one I'm having issues with does not "click" as loudly when the CTIS engages.

 

[1 Patriot-of-many]

Don't know why the DANA/Spicer CTIS troubleshooting PDF isn't a sticky, do a search for it. Lots of good info to figure out the problem.

5 Flashing Lights or DDM – Dashes "--" (Codes 26, 27)
Type: Low Pressure
Air Pressure Check
Note that the Central Tire Inflation System is not continuously
pressurized; pressure checks occur on a periodic basis. During
tire pressure checks, the system delivers compressed air
to each channel for approximately two seconds while monitoring
the pressure in that channel.
Code Description
A “Low Pressure” code indicates an extreme low pressure
reading. The most likely cause is an open line which would
have a clearly audible leak during a pressure check. A secondary
cause could be a faulty air delivery system (i.e. Pneumatic
Control Unit [PCU]Low Pressure (Codes 26, 27) electrically or
pneumatically disconnected).
Other components that can cause a Low Pressure code are:
• Electrically or pneumatically disconnected PCU
• Faulty PCU
• Restricted line between the supply tank and PCU
• Faulty PCU sensor
• Open line from PCU to Quick Release Valve
• Open line from Quick Release Valve to Wheel Valve
To correctly diagnose the faulty component, connect the Diagnostic
Tool (see "Diagnostics" for test equipment and descriptions)
and follow the procedure in the Low Pressure
troubleshooting tree.
See “Troubleshooting Tips” for general guidelines on system
diagnostics.
System Mode Condition Possible Causes (listed in order of likely occurrence)
System waits to
check pressures
Faulty pneumatic system,
or extremely low pressure
reading
• Open line between PCU and wheel valve
• Significant hub air seal leakage
• Open solenoid (PCU electrically or pneumatically disconnected)
• Crimped or plugged line between supply tank and PCU
• Faulty PCU sensor (ex. frozen water contamination)
• PCU failure, supply or control off
• Pressure switch failure, shorted closed
• Faulty ECU

 

[1 Patriot-of-many]

Don't know why the DANA/Spicer CTIS troubleshooting PDF isn't a sticky, do a search for it. Lots of good info to figure out the problem.

5 Flashing Lights or DDM – Dashes "--" (Codes 26, 27)
Type: Low Pressure
Air Pressure Check
Note that the Central Tire Inflation System is not continuously
pressurized; pressure checks occur on a periodic basis. During
tire pressure checks, the system delivers compressed air
to each channel for approximately two seconds while monitoring
the pressure in that channel.
Code Description
A “Low Pressure” code indicates an extreme low pressure
reading. The most likely cause is an open line which would
have a clearly audible leak during a pressure check. A secondary
cause could be a faulty air delivery system (i.e. Pneumatic
Control Unit [PCU]Low Pressure (Codes 26, 27) electrically or
pneumatically disconnected).
Other components that can cause a Low Pressure code are:
• Electrically or pneumatically disconnected PCU
• Faulty PCU
• Restricted line between the supply tank and PCU
• Faulty PCU sensor
• Open line from PCU to Quick Release Valve
• Open line from Quick Release Valve to Wheel Valve
To correctly diagnose the faulty component, connect the Diagnostic
Tool (see "Diagnostics" for test equipment and descriptions)
and follow the procedure in the Low Pressure
troubleshooting tree.
See “Troubleshooting Tips” for general guidelines on system
diagnostics.
System Mode Condition Possible Causes (listed in order of likely occurrence)
System waits to
check pressures
Faulty pneumatic system,
or extremely low pressure
reading
• Open line between PCU and wheel valve
• Significant hub air seal leakage
• Open solenoid (PCU electrically or pneumatically disconnected)
• Crimped or plugged line between supply tank and PCU
• Faulty PCU sensor (ex. frozen water contamination)
• PCU failure, supply or control off
• Pressure switch failure, shorted closed
• Faulty ECU

I had a bad solenoid on one of trucks. Try holding the run flat button down for a couple seconds and see if it starts inflating.

 

[RobertoGatos]

1 Patriot-of-many Thanks for posting. Read through the trouble shooting pdf awhile back. Wish I had the diagnostic tool! Is the PCU sensor what the TM calls the "pressure transducer"? If so, I already replaced that when swapping out the pneumatic controller.

Its my understanding that when flashing 5 red lights, you cannot override the system by pressing run flat. It stays in the failure mode (for me at least).

 

[1 Patriot-of-many]

No, I have that happen on a couple of my trucks and the run flat overrides it, at least on mine. I'd start by swapping out or testing the PCU. Testing the PCU for continuity is somewhere in that pdf. I used it precisely for that and found I had a bad solenoid. Swapped out one of my other trucks for it and worked. Those solenoids can be bought and spliced in to replace the bad one or just find someone parting out an A2 truck. Someone had posted not too long ago where and what solenoids he used. Just make sure you are testing the right contacts on the pcu, you might have to look at your cable, it's a little confusing from the pics.

Are you sure you swapped out a known good unit? The pressure transducer is that square block top unit that attaches to the PCU AFAIK.

 

[RobertoGatos]

Yeah, all the parts I swapped are operable. Thinking I might need to check for continuity between the PCU and brain?

 

[1 Patriot-of-many]

Yeah, all the parts I swapped are operable. Thinking I might need to check for continuity between the PCU and brain?

Yeah that's one of the possibilities, according to what I've read it's a rarity for the brain itself to be the culprit but you never know. Wish i had the tool too, it would make it much simpler to narrow down the problem. Good luck. Nice you got one of the upgraded roll over cabs i see!

 

[Suprman]

Take an air hose from your compressor with the truck off and feed air into the valve body output. You want to be over 40psi. Search for leaks. They are hard to find with the system on it senses and goes into protect very rapidly. A common place for an air leak are the rear wheel valve feed stems coming out of the hub on the style that is held on with a pressure fitting. The whole valve slips up a bit but you won't notice it just from looking.

 

[dfwernig]

You can do the continuity test that is specified in the TM. Only requires a continuity tester, couple bucks at Auto Zone. If you need a solenoid, this should be the part.

http://www.ebay.com/itm/New-Peter-P...-/260849425693?rd=1&ssPageName=STRK:MERFB:IID