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CTIS 5 flashing lights

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Ronmar

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Well if you had a really restricted feed, it might cause the controller to not see the expected result of an inflate cycle, but so coukd a wonky pressure sensor circuit, or excessive leakage...
 
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GeneralDisorder

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LMTV89 said:
Yes, and after I idle for a few I can kill the power and restart and its good. Sometimes take 2 or 3 tries but I will drive with a HWY light.
Click to expand...
If you have significant tire pressure imbalances it can have a hard time till the system gets them equalized. Check your tire pressures before you startup the truck and make sure they are all even then see what it does. The most common issue with CTIS is leaking tires or bad wheel valves.
 
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Ronmar

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General beat me to it. Tire imbalance will cause this. After it has been sitting, Walk around with a tire pressure gauge and check all the tires before a startup To figure out which wheel valve is leaking. Another giveaway for this is to shutdown the truck, get in under the truck and put a baloon or rubber glove over the exhaust horn on the dump valves. If it inflates, you have a wheel valve leaking and feeding air to the dump exhaust port.

CTIS controls these 4 air bombs we roll around on with a pea-brained processor using a lookup table, stop watch and a pressure sensor. It is expecting certain things to happen in a certain amount of time, and it is expecting pressure to be stable when it checks it. If you have a low tire, when CTIS seals the system, gives a shot of air to open the wheel valves and looks to measure pressure, the pressure is unstable as air flows to the low tire, and it faults…

The same thing happens if you change the load significantly. It will flunk the first pressure test as the weight on the rear axle has significantly changed the tire pressures on that axle.
 
Keith Knight

Keith Knight

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The Diagnostic cable and software should be here today but the PCU rebuilt kit won’t be here till next week. While waiting to receive the cable to connect to the computer I pulled the PCU out. Took it apart nothing crazy, looked clean. But decided to find enough o-rings at the local hardware store to half way rebuild it so I could put it back together and test the ECU for codes.
Hooked the PCU up and connected the short air lines ending just before the dump valves. Guess what it’s working properly, then reconnected just the front system all the way to the tires and it still works lastly reconnected the rear system all the way to the tires and still working.

So it must have been something sticking or leaking in the PCU. I will pull the PCU back apart and completely rebuild it when I get the parts in.
Does the ECU hold old codes that I can pull?
 
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Lostchain

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good question, i know I have seen historic on mine when I was working on my 4 light problem, but I can't say i recall how many times I had power cycled the truck
 
Keith Knight

Keith Knight

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I did but it only showed me the last 3 codes. And one of the last things I did while troubleshooting I accidentally left the 6 pin connector off of the solenoids. So those were the codes. I received the PCU rebuild kit, super easy to rebuild put a little oring silicone lubricant on everything and it’s working perfectly.
I would definitely recommend any using the original CTIS to rebuild it. So now I have an entirely new CTIS system minus hoses and dump valves.
While I was in the programming of the CTIS I noticed the axle ratio 4.11. Question I have is I changed to the high speed gears 3.07 years ago and had caterpillar reprogram the ECU speedometer so it’s correct. But I’m wondering if I should change the CTIS and if so what is the axle ratio I should enter. Also I can access the ABS is there a setting ing there as well? Or by changing the caterpillar ECU does that take care of everything else???
 
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Ronmar

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4.11 isnt an LMTV ratio... 3.9 is...(I wish we had 4.11:))...

CTIS on the A0 counts output speed pulses from the trans and determines speed to compare against its lookup table for selected pressure to determine overspeed. Not sure if the newer trucks pull speed info off of the data bus or still count pulses...
 
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