Jrgrain

I have a 2007 Mack 460. It has a slight miss and a lack of power. The dealer said new engine harness, injectors and lines. 5k later no difference. I have another 07 with the same motor and a buddy with a couple Mack’s 2001-2007. So I am looking for ideas on what to do about the miss and lack of power or recommendations on a laptop I can purchase to reflash my ecm and diagnose my own trucks seeing the dealer is not much help

I have a new to me 07 ct713. The lighting bolt light has been on since I got it. I did the fault code test and came up with 3-1. What do I do to fix this? Replace the exhaust temp sensor? Any help would be great.