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Hi and Welcome to the Site!
So, the simple fact is that CTIS has nothing to do with your radiator. I mean I know that both things happened at the same time - but they aren't connected by plumbing - in any way. There are several valves in the CTIS system.
So, take a look at this thread:
Hi together i had my first weekend trip yesterday with my A2. Not long, only 50km. The Beast swing sometimes. If i start the truck the tires fill up (one or two tires lose air if it´s longer as a week not startet). But the the HWY lamp flash and show that it fill or try to fill. After 1 hour...
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The filter could be stopped up.
Remove it and soak it in brake parts cleaner.
Get the system all up to pressure, Shut engine down and restart truck. Press the highway mode if it clicks then you hear some air moving in the valve body on the floor then the valves outside makes a noise and then all the lights flash....
If when you push the button it just flashes and flashes then all five start flashing it is not seeing the correct pressure in the secondary wet tank. I had this problem and just jumper-ed the switch. the down side to this is there is a possibility, be it a slight one that the tires can be filling up and you can loose brakes. I have had this bypassed for a while now and it airs the tires up so slow that I have never seen my secondary pressure drop bellow 100psi when airing up the tires. Jump switch at cannon plug and see if system operates.
You might also read the few page summary on CTIS attached below