Low tire sensor kept going off. kept taking vehicle to north cascade ford and les schwab tire centers to have sensors reset and tires checked. different tires at different times were low. started at approximately 41000 miles. on october 7,2017 front driver tire was completely flat. aired it up and went to les schwab. after checking all 4 tires and not finding any problem with the tires, which were purchased at les schwab the tire technician found that three of the four wheels that came on the vehicle when purchased (purchased new from north cascade ford) were cracked and allowing air from the tires to leak out. called the service department at north cascade ford and the only response was the warranty has expired, suggested a call to ford customer service which resulted in a conversation with a person who did not dpeak english very understandably saying they would focument the phone call. les schwab tire center did document the cracked wheels on the invoice of the new wheels that were purchased from them.