I took my Sonata in for service campaign 953 last week. I have noticed upon return of my vehicle several issues that have emerged post 953 knock sensor detection system software update. I am feeling a pulsating shuttering vibration whenever I am depressing the brake pedal. It does vary in intensity. I have also noticed that when idling on a cold start the needle of the tachometer will very nervously increase and decrease in engine speed. Last but not least is the automatic electronic climate control has really lost it's mind. I can hear the front defroster operating when it is not activated. The automatic fan setting will prematurely blow out cold air from the vents before it is properly heated. In order to receive any heat at all, I will have to increase the temperature to a much higher temperature setting than I did before. Prior to the Service Campaign 953 software update, I never once experienced any of the above mentioned problems. Has anyone else experienced the same problems or is able to shed some light on this??? Thank you so much.

 

Since this should all be covered by warranty, suggest you return it to shop that did the work and have them fix it.