MHC Kenworth - Cheyenne

On 4/22/20 my check engine light came on my *** semi truck. I called MHC Kenworth and was told they were able to look at it. I drove my semi into their repair shop and they connected it to the diagnostic computer. The tech advised me the code was for abnormal crankcase pressure. I was advised they wanted to do a blow by test. The test was performed and it was found to be in spec. The tech stated "it may need a new crankcase filter". I informed the tech the filter was replaced less than one month prior. He also stated the sensor could be bad. The tech performed the test on the sensor and replaced the sensor. My check engine light turned off. The repair shop said I was good to go. After reviewing the bill, the tech stated in his write up that the original sensor tested fine but he still replaced it. I asked why the sensor was replaced if it tested okay? He replied sometimes they will test good and still send a fault code.
The bill amount was for $926.17, which I paid in full. I left the repair shop to continue on my route. I drove 45 miles west and the check engine light came back on. I called MHC back. They said to bring it back in. I told the service manager that it was not a good idea as the truck was fully loaded. Returning would have involved going back up over a 10,000 foot mountain with a check engine light on. He replied that was a wise decision. I told him I was going to Rawlings, WY, as that was a safer route, to have it looked at the next morning at Elk Mountain Diesel. Within 30 minutes they had the semi diagnosed with a cracked air to air cooler.The engine will not initiate a code for air to air as it is not electronically controlled. But it will cause multiple other codes as it did. I asked them if that would cause the engine codes for crankcase pressure and low boost. They replied yes. I also called *** and *** to verify. Both shops were also confirmed a cracked air to air would cause those codes. $2500.00 later it was fixed!