Dodgeviking

Hey crew. I have had issues with my 2012 turbo 6.7 I did an egr clean last January and it keeps throwing me a check engine light the code says it is for the exhaust sensor but I have replaced that on more than one occasion. Also clean that sensor during routine. I have taken it in to see what they come up with and they just want me to fix it for 600.00 even though I have told them that's not the problem. Any one have any suggestions as what else it could be? Thanks